The progressive failure characteristics of geomaterial are a remarkable and challenging topic in geotechnical engineering.To study the effect of salt content and temperature on the progressive failure characteristics ...The progressive failure characteristics of geomaterial are a remarkable and challenging topic in geotechnical engineering.To study the effect of salt content and temperature on the progressive failure characteristics of frozen sodium sulfate saline sandy soil,a series of uniaxial compression tests were performed by integrating digital image correlation(DIC)technology into the testing apparatus.The evolution law of the uniaxial compression strength(UCS),the failure strain,and the formation of the shear band of the frozen sodium sulfate saline sandy soil were analyzed.The test results show that within the scope of this study,with the increase of salt content,both the UCS and the shear band angle initially decrease with increasing salt content before showing an increase.In contrast,the failure strain and the width of the shear band exhibit an initial increase followed by a decrease in the samples.In addition,to investigate the brittle failure characteristics of frozen sodium sulfate saline sandy soil,two classic brittleness evaluation methods were employed to quantitatively assess the brittleness level for the soil samples.The findings suggest that the failure characteristics under all test conditions in this study belong to the transition stage between brittle and ductile,indicating that frozen sodium sulfate saline sandy soil exhibits certain brittle behavior under uniaxial compression conditions,and the brittleness index basically decreases and then increases with the rise in salt content.展开更多
To investigate the temperature susceptibility and nonlinear memory effects of artificially frozen soil creep behavior,this study conducted uniaxial step-loading creep tests under controlled temperatures ranging from-1...To investigate the temperature susceptibility and nonlinear memory effects of artificially frozen soil creep behavior,this study conducted uniaxial step-loading creep tests under controlled temperatures ranging from-10℃to-20℃.The transient creep characteristics and steady-state creep rates of artificially frozen soils were systematically examined with respect to variations in temperature and stress.Experimental results demonstrate that decreasing temperatures lead to a decaying trend in the steady-state creep rate of silty frozen soil,confirming that low-temperature environments significantly inhibit plastic flow while enhancing material stiffness.Based on fractional calculus theory,a fractional derivative creep model was established.By incorporating temperature dependencies,the model was further improved to account for both stress and temperature effects.The model predictions align closely with experimental data,achieving over 91%agreement(standard deviation±1.8%),and effectively capture the stress-strain behavior of artificially frozen soil under varying thermal conditions.This research provides a reliable theoretical foundation for studying deformation characteristics in cold-regions engineering.展开更多
Due to the high water content in warm frozen soil,the pore water pressure and pore ice pressure generated within the sample during loading significantlyinfluencethe deformation and strength of the soil skeleton.Theref...Due to the high water content in warm frozen soil,the pore water pressure and pore ice pressure generated within the sample during loading significantlyinfluencethe deformation and strength of the soil skeleton.Therefore,it is essential to develop a constitutive model for warm frozen soil that can capture the changes in ice pressure and water pressure.This study introduces a macro-meso constitutive model based on a binary-medium framework to describe the mechanical behavior of warm frozen soil.In this model,warm frozen soil is conceptualized as consisting of bonded and frictional elements from a meso perspective.The bonded elements are modeled using a macro-meso elastic constitutive approach based on poromechanics,while the frictional elements employ a macro-meso elastoplastic approach,also grounded in poromechanics.These two elements are then linked within the binarymedium model framework.By replicating the experimental curves of warm frozen soils,the theoretical results from the proposed model show excellent agreement with experimental data.This consistency indicates that the model effectively simulates the strain softening and volumetric expansion behaviors of warm frozen soil samples under various conditions.Additionally,the constitutive model predicts changes in unfrozen water pressure,frozen temperature,unfrozen water saturation,and porosity during the loading process of warm frozen soil samples.展开更多
Frost heave and thaw settlement in cold regions pose a significant threat to engineering construction.Optical frequency domain reflectometry(OFDR)based on Rayleigh scattering can be applied to monitor ground deformati...Frost heave and thaw settlement in cold regions pose a significant threat to engineering construction.Optical frequency domain reflectometry(OFDR)based on Rayleigh scattering can be applied to monitor ground deformation in frozen soil areas,where the interface behavior of soil-embedded fiber optic sensors governs the monitoring accuracy.In this paper,a series of pullout tests were conducted on fiber optic(FO)cables embedded in the frozen soil to investigate the cable‒soil interface behavior.An experimental study was performed on interaction effects,particularly focused on the water content of unfrozen soil,freezing duration,and differential distribution of water content in frozen soil.The highresolution axial strains of FO cables were obtained using a sensing interrogator,and were used to calculate the interface shear stress.The interfacial mechanical response was analytically modeled using the ideal elasto‒plastic and softening constitutive models.Three freezing periods,correlating with the phase change process between ice and water,were analyzed.The results shows that the freezing effect can amplify the peak shear stress at the cable-soil interface by eight times.A criterion for the interface coupling states was proposed by normalizing the pullout force‒displacement information.Additionally,the applicability of existing theoretical models was discussed by comparing the results of theoretical back‒calculations with experimental measurements.This study provides new insights into the progressive interfacial failure behavior between strain sensing cable and frozen soil,which can be used to assist the interpretation of FO monitoring results of frozen soil deformation.展开更多
According to the announcement of General Administration of Quality Supervision,Inspection and Quarantine of the People's Republic of China,the risk of microbial items in frozen drinks is very high,and it is diffic...According to the announcement of General Administration of Quality Supervision,Inspection and Quarantine of the People's Republic of China,the risk of microbial items in frozen drinks is very high,and it is difficult to improve.For example,a recent spot check showed that 42 kinds of frozen drinks had microbial indicators exceeding the standard.Part of the reason is that the design of the production workshop is not conducive to the rapid removal of production water,resulting in continuous moisture throughout the workshop,which provides a breeding bed for microorganisms to breed and then contaminates the product.Therefore,research is carried out from the design point of view to fundamentally reduce the moisture in the workshop and build a dry workshop for frozen drinks production,so as to effectively reduce the risk of microbial contamination of frozen drinks.展开更多
Here,a seismic-response analysis model was proposed for evaluating the nonlinear seismic response of a pile-supported bridge pier under frozen and thawed soil conditions.The effect of a seasonally frozen soil layer on...Here,a seismic-response analysis model was proposed for evaluating the nonlinear seismic response of a pile-supported bridge pier under frozen and thawed soil conditions.The effect of a seasonally frozen soil layer on the seismic vulnerability of a pile-supported bridge pier was evaluated based on reliability theory.Although the frozen soil layer inhibited the seismic response of the ground surface to a certain extent,it exacerbated the acceleration response at the bridge pier top owing to the low radiation damping effect of the frozen soil layer.Furthermore,the frozen soil layer reduced the lateral displacement of the bridge pier top relative to the ground surface by approximately 80%,thereby preventing damage caused by earthquakes,such as falling girders.Compared to the thawed state of the ground surface,the bending moment of the bridge pier in frozen ground increases.However,the bending moment of the pile foundation in frozen ground decreases,thereby lessening the seismic vulnerability of the bridge pile foundation.The results of this can provide a reference for the seismic response analysis and seismic risk assessment of pile-supported bridges in seasonally frozen regions.展开更多
Objective:This study aims to develop a deep multiscale image learning system(DMILS)to differentiate malignant from benign thyroid follicular neoplasms on multiscale whole-slide images(WSIs)of intraoperative frozen pat...Objective:This study aims to develop a deep multiscale image learning system(DMILS)to differentiate malignant from benign thyroid follicular neoplasms on multiscale whole-slide images(WSIs)of intraoperative frozen pathological images.Methods:A total of 1,213 patients were divided into training and validation sets,an internal test set,a pooled external test set,and a pooled prospective test set at three centers.DMILS was constructed using a deep learningbased weakly supervised method based on multiscale WSIs at 10×,20×,and 40×magnifications.The performance of the DMILS was compared with that of a single magnification and validated in two pathologist-unidentified subsets.Results:The DMILS yielded good performance,with areas under the receiver operating characteristic curves(AUCs)of 0.848,0.857,0.810,and 0.787 in the training and validation sets,internal test set,pooled external test set,and pooled prospective test set,respectively.The AUC of the DMILS was higher than that of a single magnification,with 0.788 of 10×,0.824 of 20×,and 0.775 of 40×in the internal test set.Moreover,DMILS yielded satisfactory performance on the two pathologist-unidentified subsets.Furthermore,the most indicative region predicted by DMILS is the follicular epithelium.Conclusions:DMILS has good performance in differentiating thyroid follicular neoplasms on multiscale WSIs of intraoperative frozen pathological images.展开更多
The artificial ground-freezing method is the main technical means for the excavation of mines and tunnels through the water-rich sand layer,and the comprehensive understanding of the mechanical properties of frozen sa...The artificial ground-freezing method is the main technical means for the excavation of mines and tunnels through the water-rich sand layer,and the comprehensive understanding of the mechanical properties of frozen saturated sand and the stress-strain relationship under complex stress can provide important guidance.In this study,a series of true triaxial tests of frozen saturated sand samples were conducted.Combined with the test data,the effects of temperature and medium principal stress ratio(b)on the strength and deformation characteristics of frozen saturated sand are discussed.In addition,a cohesion tensor is introduced to the Wu-Lin hypoplastic model.A scalar value is used to characterize the effect of temperature on the strength of frozen soil.The defect that the original model cannot describe the tensile capacity of frozen soil under low stress conditions is clearly solved.In addition,the cumulative deformation state variable is introduced to improve the response performance of the model in triaxial compression tests.The hypoplastic model of frozen soil has shown good performance in simulating triaxial compression tests at different temperatures and medium principal stress ratios.展开更多
The pile-plate structure has proven highly effective support for high-speed railway subgrades,particularly in poor geological conditions.Although its efficacy in non-frozen regions is well-established,its potential in...The pile-plate structure has proven highly effective support for high-speed railway subgrades,particularly in poor geological conditions.Although its efficacy in non-frozen regions is well-established,its potential in frozen regions remains underexplored.In seasonally frozen areas,F-T(freeze-thaw)cycles threaten subgrade stability,necessitating research on pile-plate structure’s behavior under such conditions.To address this challenge,a scaled model experiment was conducted on a silty sand foundation,simulating F-T cycles using temperature control devices.Key parameters,including soil temperature,frozen depth,and displacement,were systematically monitored.Results indicate that the bearing plate functions as an effective insulation layer,significantly reducing sub-zero temperature penetration.Additionally,the anchoring action of the piles mitigates frost heave in the foundation soil,while the plate middle restrains soil deformation more effectively due to increased constraint.The thermal insulation provided by the plate maintains higher soil temperatures,delaying the onset of freezing.By the end of each freezing stage,the vertical displacement in the natural subgrade is approximately 4 times greater than that beneath the pile-plate structure.Furthermore,the frost depth is about 1.3-1.4 times and 1.6-4.9 times greater than that measured below the plate edge and middle,respectively.These insights contribute to the development of more resilient designs for high-speed railway subgrades in seasonally frozen regions,offering engineers a robust,scientifically-backed foundation for future infrastructure projects.展开更多
To ensure the safe operation of trains in seasonally frozen regions, achieving accurate and interpretable displacement prediction of tunnel portal slopes is a fundamental requirement. In this paper, we developed a hyb...To ensure the safe operation of trains in seasonally frozen regions, achieving accurate and interpretable displacement prediction of tunnel portal slopes is a fundamental requirement. In this paper, we developed a hybrid prediction model that integrates dual signal decomposition with an interpretable deep neural network. The Complete Ensemble Empirical Mode Decomposition with Adaptive Noise(CEEMDAN) first decomposes the original signals, then performs mode selection and reconstruction based on sample entropy and clustering to suppress redundancy. The high-frequency components are further analyzed using VMD and optimized via DLABC, thereby enhancing multi-scale dynamic feature extraction. On this basis, a Convolutional Neural Network(CNN)-Long Short-Term Memory(LSTM)-Attention model, tuned by the Dung Beetle Optimizer(DBO), is constructed to jointly capture local features, temporal dependencies, and key time-specific responses. Results show the proposed model achieves R^(2)>0.99 and MSE<0.07 across multiple monitoring points, significantly outperforming single-decomposition models(e.g., VMD-BP, R^(2)=0.896, MSE=1.700). The dual decomposition strategy proves effective in noise suppression and feature enhancement. Additionally, the SHapley Additive ex Planations(SHAP) analysis visualizes the model's decision process, quantifying the contribution of key factors to slope deformation, thus improving transparency and reliability. The model demonstrates specific adaptability to freeze-thaw environments, providing a robust framework for forecasting slope deformation and issuing early warnings in seasonally frozen regions.展开更多
Objective To assess the efficacy and possible adverse effects of acupuncture on frozen shoulder. Methods Based on the key words, i.e. acupuncture, electroacupuncture, acupuncture-moxibustion, frozen shoulder, adhesive...Objective To assess the efficacy and possible adverse effects of acupuncture on frozen shoulder. Methods Based on the key words, i.e. acupuncture, electroacupuncture, acupuncture-moxibustion, frozen shoulder, adhesive capsulitis, shoulder disorders etc., the Chinese databases were retrieved, including Oochrane Musculoskeleta Group, Oochrane Controlled Trials Register, Oochrane Complementary Medicine Field, and the central database of the Oochrane Library as well as MEDLINE, EMBASE and Chinese Biomedical CD （OBM-disc）. 20 Chinese medical journals and relevant academic conference proceedings have been searched manually. The reference lists of identified documents were checked as the supplementary retrieval. Results 6 randomized controlled trials on frozen shoulder with acupuncture and electroacupuncture were included, indicating quite advanced study quality. There were 34 to 257 participants in the trials, 668 in total. The total OR of CMS/OSA was OR 3.49 （95 % CI - 2.64 to 9.63）, the total OR of VAS was OR - 1.24 （95% CI -3.50 to 1.01）, the total OR of ROM was OR 35.70 （95% CI 22.91 to 48.49）; the total OR of MELLE was OR 4.30 （95% OI 2.32 to 7.98）. Conclusion It is shown in the present limited inclusive trials on frozen shoulder that acupuncture is the safe therapy and effective on improving the global function, relieving pain, and improving the range of motion of shoulder. All the therapeutic effects of acupuncture are superior to those in control group. However, much more high quality trials are required to provide much stronger evidence. Additionally, much more evidences on validity of frozen shoulder with other assessing indexes involved are required in the treatment with acupuncture.展开更多
Objective To explore better therapies for the treatment of frozen shoulder. Methods One hundred and seventy-four cases were divided into a filiform needle group （56 cases）, an electroacupuncture group （57 cases） a...Objective To explore better therapies for the treatment of frozen shoulder. Methods One hundred and seventy-four cases were divided into a filiform needle group （56 cases）, an electroacupuncture group （57 cases） and a warming needle group （61 cases） according to the randomized, controlled and single-blind study principles. Jiānqián （肩前 Extra）, Jiānyú （肩髃 LI 15）, Jiānliáo （肩髎 TE 14）, Nàoshū （臑俞 SI 10）, Wàiguān （外关 TE 5）, Hégǔ （合谷 LI 4） were used in all three groups but treated with filiform needle, electroacupuncture and warming needle technique respectively. The needles were retained for 30 min. It was given once every other day and 5 times constituted as one course. Pain indices and activity degree of shoulders were measured and recorded before and after treatment every time. Results The total effective rate was 93.0% （53/57） in the electroacupuncture group and 95.1% （58/61） in the warming needle group, both superior to that of 78.6% （44/56） in the filiform needle group （both P〈0.01）, but there was no significant difference between electroacupuncture group and warming needle group （P〉0.05）. After one course of treatment, the decline indices of shoulder pain of electroacupuncture group （4.28±0.22） and warming needle group （3.74±0.17） were both significantly greater than that of filiform needle group （2.78±0.18）（both P〈0.01）. And the decline indices of electroacupuncture group was also greater than that of warming needle group （P〈0.05）. The improvements of shoulder activity degree of warming needle group （76.92±5.53） and electroacupuncture group （60.37±3.80） were both greater than that of filiform needle group （42.50±3.67） （both P〈0.01）. And shoulder activity degree of warming needle group was also greater than that of electroacupuncture group （P〈0.01）. After one course of treatment, improvement of shoulder activity degree and decline indices of shoulder pain in these three groups were better than that after the first time treatment （all P〈0.01）. Conclusion All these three acupuncture therapies can achieve good therapeutic effects for frozen shoulder. The therapeutic effects of electroacupuncture and warming needle groups are superior to that of filiform needle group. All these three therapies could significantly reduce patients’ pain and improve their shoulder activity degree. The analgesic effect of electroacupuncture is the best, and the shoulder activity degree improved by warming needle is the best. The improvement of clinical therapeutic effect mainly depends on the therapy and the treatment times when the same acupoints are selected and the condition of illness are similar.展开更多
To study the influence of temperature and water content on ultrasonic wave velocity and to establish the relationship between ultrasonic wave velocity and frozen silty clay strength, ultrasonic tests were conducted to...To study the influence of temperature and water content on ultrasonic wave velocity and to establish the relationship between ultrasonic wave velocity and frozen silty clay strength, ultrasonic tests were conducted to frozen silty clay by using RSM-SY5（T） nonmetal supersonic test meter, and the tensile strength and compressive strength of silty clay were measured under various negative temperatures. Test and analysis results indicate that, ultrasonic wave velocity rapidly changes in the temperature range of-1 ℃ to -5 ℃. Ultrasonic wave velocity increased with an increase of water content until the water content reached the critical water content, while decreased with an increase of water content after the water content exceeded the critical water content. This study showed that there was strong positive correlation between the ul- trasonic wave velocity and the frozen soil strength. As ultrasonic wave velocity increased, either tensile strength or com- pressive strength increased. Based on the experimental data, the relationship between ultrasonic wave velocity and frozen silty clay strength was obtained through regression analysis. It was found that the ultrasonic test technique can be used to test frozen soils and lay the foundation for the determination of frozen soil strength.展开更多
Determining the mechanical properties of frozen rock is highly important in cold-area engineering.These properties are essentially correlated with the content of liquid water remaining in frozen rock.Therefore,accurat...Determining the mechanical properties of frozen rock is highly important in cold-area engineering.These properties are essentially correlated with the content of liquid water remaining in frozen rock.Therefore,accurate determination of unfrozen water content could allow rapid evaluation of mechanical properties of frozen rock.This paper investigates the hysteresis characteristics of ultrasonic waves applied to sandstone(in terms of the parameters of P-wave velocity,amplitude,dominant frequency and quality factor Q)and their relationships with unfrozen water content during the freeze-thaw process.Their correlations are analysed in terms of their potential for use as indicators of freezing state and unfrozen water content.The results show that:(1)During a freeze-thaw cycle,the ultrasonic parameters and unfrozen water content of sandstone have significant hysteresis with changes in temperature.(2)There are three clear stages of change during freezing:supercooled stage(0℃to-2℃),rapid freezing stage(-2℃to-3℃),and stable freezing stage(-3℃to-20℃).The changes in unfrozen water content and ultrasonic parameters with freezing temperature are inverse.(3)During a single freeze-thaw cycle,the ultrasonic parameters of sandstone are significantly correlated with its unfrozen water content,and this correlation is affected by the pore structure.For sandstones with mesopores greater than 50%,there are inflection points in the curves of ultrasonic parameters vs.unfrozen water content at-3℃during freezing and at-1℃during thawing.It was found that thermal deformation of the mineral-grain skeleton and variations in the phase composition of pore water change the propagation path of ultrasonic waves.The inflection point in the curve of dominant frequency vs.temperature clearly marks the end of the rapid freezing stage of pore water,in which more than 70%of the pore water freezes.Consequently,the dominant frequency can be used as an index to conveniently estimate the unfrozen water content of frozen rock and,hence,its mechanical properties.展开更多
Due to the presence of ice and unfrozen water in pores of frozen rock,the rock fracture behaviors are susceptible to temperature.In this study,the potential thawing-induced softening effects on the fracture behaviors ...Due to the presence of ice and unfrozen water in pores of frozen rock,the rock fracture behaviors are susceptible to temperature.In this study,the potential thawing-induced softening effects on the fracture behaviors of frozen rock is evaluated by testing the tension fracture toughness(KIC)of frozen rock at different temperatures(i.e.-20℃,-15℃,-12℃,-10℃,-8℃,-6℃,-4℃,-2℃,and 0℃).Acoustic emission(AE)and digital image correlation(DIC)methods are utilized to analyze the microcrack propagation during fracturing.The melting of pore ice is measured using nuclear magnetic resonance(NMR)method.The results indicate that:(1)The KIC of frozen rock decreases moderately between-20℃ and-4℃,and rapidly between-4℃ and 0℃.(2)At-20℃ to-4℃,the fracturing process,deduced from the DIC results at the notch tip,exhibits three stages:elastic deformation,microcrack propagation and microcrack coalescence.However,at-4℃e0℃,only the latter two stages are observed.(3)At-4℃e0℃,the AE activities during fracturing are less than that at-20℃ to-4℃,while more small events are reported.(4)The NMR results demonstrate a reverse variation trend in pore ice content with increasing temperature,that is,a moderate decrease is followed by a sharp decrease and-4℃ is exactly the critical temperature.Next,we interpret the thawing-induced softening effect by linking the evolution in microscopic structure of frozen rock with its macroscopic fracture behaviors as follow:from-20℃ to-4℃,the thickening of the unfrozen water film diminishes the cementation strength between ice and rock skeleton,leading to the decrease in fracture parameters.From-4℃ to 0℃,the cementation effect of ice almost vanishes,and the filling effect of pore ice is reduced significantly,which facilitates microcrack propagation and thus the easier fracture of frozen rocks.展开更多
The acquisition of spatial-temporal information of frozen soil is fundamental for the study of frozen soil dynamics and its feedback to climate change in cold regions.With advancement of remote sensing and better unde...The acquisition of spatial-temporal information of frozen soil is fundamental for the study of frozen soil dynamics and its feedback to climate change in cold regions.With advancement of remote sensing and better understanding of frozen soil dynamics,discrimination of freeze and thaw status of surface soil based on passive microwave remote sensing and numerical simulation of frozen soil processes under water and heat transfer principles provides valuable means for regional and global frozen soil dynamic monitoring and systematic spatial-temporal responses to global change.However,as an important data source of frozen soil processes,remotely sensed information has not yet been fully utilized in the numerical simulation of frozen soil processes.Although great progress has been made in remote sensing and frozen soil physics,yet few frozen soil research has been done on the application of remotely sensed information in association with the numerical model for frozen soil process studies.In the present study,a distributed numerical model for frozen soil dynamic studies based on coupled water-heat transferring theory in association with remotely sensed frozen soil datasets was developed.In order to reduce the uncertainty of the simulation,the remotely sensed frozen soil information was used to monitor and modify relevant parameters in the process of model simulation.The remotely sensed information and numerically simulated spatial-temporal frozen soil processes were validated by in-situ field observations in cold regions near the town of Naqu on the East-Central Tibetan Plateau.The results suggest that the overall accuracy of the algorithm for discriminating freeze and thaw status of surface soil based on passive microwave remote sensing was more than 95%.These results provided an accurate initial freeze and thaw status of surface soil for coupling and calibrating the numerical model of this study.The numerically simulated frozen soil processes demonstrated good performance of the distributed numerical model based on the coupled water-heat transferring theory.The relatively larger uncertainties of the numerical model were found in alternating periods between freezing and thawing of surface soil.The average accuracy increased by about 5%after integrating remotely sensed information on the surface soil.The simulation accuracy was significantly improved,especially in transition periods between freezing and thawing of the surface soil.展开更多
Adopting the quasi-three-dimensional （Quasi-3D） numerical method to optimize the anti-freeze design parameters of an underground pipeline usually involves heavy numerical calculations. Here, the fitting formulae bet...Adopting the quasi-three-dimensional （Quasi-3D） numerical method to optimize the anti-freeze design parameters of an underground pipeline usually involves heavy numerical calculations. Here, the fitting formulae between the safe con-veyance distance （SCD） of a water pipeline and six influencing factors are established based on the lowest water temper-ature （LWT） along the pipeline axis direction. With reference to the current widely used anti-freeze design approaches for underground pipelines in seasonally frozen areas, this paper first analyzes the feasibility of applying the maximum frozen penetration （MFP） instead of the mean annual ground surface temperature （MAGST） and soil water content （SWC） to calculate the SCD. The results show that the SCD depends on the buried depth if the MFP is fixed and the variation of the MAGST and SWC combination does not significantly change the SCD. A comprehensive formula for the SCD is estab-lished based on the relationships between the SCD and several primary influencing factors and the interaction among them. This formula involves five easy-to-access parameters： the MFP, buried depth, pipeline diameter, flow velocity, and inlet water temperature. A comparison between the analytical method and the numerical results based on the Quasi-3D method indicates that the two methods are in good agreement overall. The analytic method can be used to optimize the anti-freeze design parameters of underground water pipelines in seasonally frozen areas under the condition of a 1.5 safety coefficient.展开更多
Ultrasonic P-wave tests of frozen silt and frozen sand were conducted during uniaxial loading by using an RSM^-SY5（T） nonmetal ultrasonic test meter to study the velocity characteristics of P-waves. The experimental...Ultrasonic P-wave tests of frozen silt and frozen sand were conducted during uniaxial loading by using an RSM^-SY5（T） nonmetal ultrasonic test meter to study the velocity characteristics of P-waves. The experimental results indicate that the P-wave velocity is affected by soil materials, temperature, and external loads, so the P-wave velocity is different in frozen silt and frozen sand, but all decrease with an increase of temperature and increase at first and then decrease with strain during the loading process. There is an exponential relationship between uniaxial compressive strength and P-wave ve- locity, and the correlation between them is very good. The characteristic parameters of acoustic waves can, to some extent, reflect the development of internal cracks in frozen soils during loading.展开更多
In permafrost regions with warm frozen soil,subgrade thaw-collapse phenomenon commonly occurs,facing thaw collapse problems of the existed frozen soil subgrade,thus it is difficult to use traditional methods such as a...In permafrost regions with warm frozen soil,subgrade thaw-collapse phenomenon commonly occurs,facing thaw collapse problems of the existed frozen soil subgrade,thus it is difficult to use traditional methods such as active cooling and passive protection technology to stabilize the existed warm frozen soil subgrade.This study derives a novel stabilizer method,a long-short(L-S)cement-mixed batter pile composite foundation to stabilize the existed warm frozen soil subgrade.To solve the thawcollapse problems in warm frozen soil subgrade,high water content and large compressibility characteristics were compared between soft soil and warm frozen soils.Theoretical analysis of heat conduction and numerical simulation of finite element model were used to study the freeze–thaw process and evaluate the stabilized effects of the L-S cement-mixed batter piles on the warm frozen soil foundation of the Qinghai-Xizang Highway.Furthermore,the thaw process and mechanical properties of foundation and piles were analyzed by introducing the hydration heat factor in the thermodynamic control equation.The results indicate that the thawing displacement of the existed warm frozen soil subgrade was reduced owing to the“support”and“grasp”effects of the L-S cement-mixed batter piles on the surrounding soil.The composite ground formed by strengthening the warm frozen ground with batter piles could considerably improve the bearing capacity of the existed warm frozen ground,effectively restrain the deformation of the upper embankment,and improve the strength of the ground.The analysis can provide method for the construction design of cement mixing batter pile foundation in cold regions.展开更多
In this study, frozen red sandstone specimens were impacted by a Split Hopkinson bar (SHPB), with a velocity of 4.558 ~ 6.823 ms-1. The temperature of the specimens was maintained at -15℃ during the experiment. For c...In this study, frozen red sandstone specimens were impacted by a Split Hopkinson bar (SHPB), with a velocity of 4.558 ~ 6.823 ms-1. The temperature of the specimens was maintained at -15℃ during the experiment. For comparison purposes, static uniaxial compression tests were conducted in advance using a freezing triaxial test machine. Four stress-strain curves were obtained in diff erent average strain rates. The test results suggested that when the average strain rate is low, the specimen strength changes gradually;but when it is high, its strength changes rapidly. When the average strain rate is 120.73 s-1, the peak value of stress is as high as 82.96 MPa, which is about two times that of the static compressive strength of 44.1 MPa. A constitutive model was established that was composed of the damaged, viscoelastic and spring bodies, and revealed the variations of compressive strength and strain for the frozen red sandstone under diff erent high strain rates. The test results also showed that the failure form was correlated to the average strain rate of the frozen red sandstone. When the average strain rate is low, the damage was only distributed on the specimen’s edges. However, as the average strain rate increases, the damage range extended to the central parts of the specimen. When the average strain rate reached 107.34s-1, the specimen was smashed.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42372312,and 42172299)the Pyramid Talent Training Project of Beijing University of Civil Engineering and Architecture(Grant No.JDYC20220807).
文摘The progressive failure characteristics of geomaterial are a remarkable and challenging topic in geotechnical engineering.To study the effect of salt content and temperature on the progressive failure characteristics of frozen sodium sulfate saline sandy soil,a series of uniaxial compression tests were performed by integrating digital image correlation(DIC)technology into the testing apparatus.The evolution law of the uniaxial compression strength(UCS),the failure strain,and the formation of the shear band of the frozen sodium sulfate saline sandy soil were analyzed.The test results show that within the scope of this study,with the increase of salt content,both the UCS and the shear band angle initially decrease with increasing salt content before showing an increase.In contrast,the failure strain and the width of the shear band exhibit an initial increase followed by a decrease in the samples.In addition,to investigate the brittle failure characteristics of frozen sodium sulfate saline sandy soil,two classic brittleness evaluation methods were employed to quantitatively assess the brittleness level for the soil samples.The findings suggest that the failure characteristics under all test conditions in this study belong to the transition stage between brittle and ductile,indicating that frozen sodium sulfate saline sandy soil exhibits certain brittle behavior under uniaxial compression conditions,and the brittleness index basically decreases and then increases with the rise in salt content.
基金National Key Research and Development Program of China“Structural Stability Assessment Techniques and Demonstration for Masonry Ancient Pagodas”(2023YFF0906005)。
文摘To investigate the temperature susceptibility and nonlinear memory effects of artificially frozen soil creep behavior,this study conducted uniaxial step-loading creep tests under controlled temperatures ranging from-10℃to-20℃.The transient creep characteristics and steady-state creep rates of artificially frozen soils were systematically examined with respect to variations in temperature and stress.Experimental results demonstrate that decreasing temperatures lead to a decaying trend in the steady-state creep rate of silty frozen soil,confirming that low-temperature environments significantly inhibit plastic flow while enhancing material stiffness.Based on fractional calculus theory,a fractional derivative creep model was established.By incorporating temperature dependencies,the model was further improved to account for both stress and temperature effects.The model predictions align closely with experimental data,achieving over 91%agreement(standard deviation±1.8%),and effectively capture the stress-strain behavior of artificially frozen soil under varying thermal conditions.This research provides a reliable theoretical foundation for studying deformation characteristics in cold-regions engineering.
基金the financial support from the funding of the National Natural Science Foundation of China(NSFC)(Grant Nos.42401160 and U22A20596)the Science and Technology Plan Project of Linzhi(Grant No.SYQ2024-13).
文摘Due to the high water content in warm frozen soil,the pore water pressure and pore ice pressure generated within the sample during loading significantlyinfluencethe deformation and strength of the soil skeleton.Therefore,it is essential to develop a constitutive model for warm frozen soil that can capture the changes in ice pressure and water pressure.This study introduces a macro-meso constitutive model based on a binary-medium framework to describe the mechanical behavior of warm frozen soil.In this model,warm frozen soil is conceptualized as consisting of bonded and frictional elements from a meso perspective.The bonded elements are modeled using a macro-meso elastic constitutive approach based on poromechanics,while the frictional elements employ a macro-meso elastoplastic approach,also grounded in poromechanics.These two elements are then linked within the binarymedium model framework.By replicating the experimental curves of warm frozen soils,the theoretical results from the proposed model show excellent agreement with experimental data.This consistency indicates that the model effectively simulates the strain softening and volumetric expansion behaviors of warm frozen soil samples under various conditions.Additionally,the constitutive model predicts changes in unfrozen water pressure,frozen temperature,unfrozen water saturation,and porosity during the loading process of warm frozen soil samples.
基金the National Key Research and Development Program of China(Grant No.2023YFF1303501)the National Science Fund for Distinguished Young Scholars of China(Grant No.42225702)the Open Fund of State Key Laboratory of Frozen Soil Engineering(Grant No.SKLFSE201814).
文摘Frost heave and thaw settlement in cold regions pose a significant threat to engineering construction.Optical frequency domain reflectometry(OFDR)based on Rayleigh scattering can be applied to monitor ground deformation in frozen soil areas,where the interface behavior of soil-embedded fiber optic sensors governs the monitoring accuracy.In this paper,a series of pullout tests were conducted on fiber optic(FO)cables embedded in the frozen soil to investigate the cable‒soil interface behavior.An experimental study was performed on interaction effects,particularly focused on the water content of unfrozen soil,freezing duration,and differential distribution of water content in frozen soil.The highresolution axial strains of FO cables were obtained using a sensing interrogator,and were used to calculate the interface shear stress.The interfacial mechanical response was analytically modeled using the ideal elasto‒plastic and softening constitutive models.Three freezing periods,correlating with the phase change process between ice and water,were analyzed.The results shows that the freezing effect can amplify the peak shear stress at the cable-soil interface by eight times.A criterion for the interface coupling states was proposed by normalizing the pullout force‒displacement information.Additionally,the applicability of existing theoretical models was discussed by comparing the results of theoretical back‒calculations with experimental measurements.This study provides new insights into the progressive interfacial failure behavior between strain sensing cable and frozen soil,which can be used to assist the interpretation of FO monitoring results of frozen soil deformation.
文摘According to the announcement of General Administration of Quality Supervision,Inspection and Quarantine of the People's Republic of China,the risk of microbial items in frozen drinks is very high,and it is difficult to improve.For example,a recent spot check showed that 42 kinds of frozen drinks had microbial indicators exceeding the standard.Part of the reason is that the design of the production workshop is not conducive to the rapid removal of production water,resulting in continuous moisture throughout the workshop,which provides a breeding bed for microorganisms to breed and then contaminates the product.Therefore,research is carried out from the design point of view to fundamentally reduce the moisture in the workshop and build a dry workshop for frozen drinks production,so as to effectively reduce the risk of microbial contamination of frozen drinks.
基金National Natural Science Foundation of China under Grant Nos.52068045,U21A2012 and 41825015。
文摘Here,a seismic-response analysis model was proposed for evaluating the nonlinear seismic response of a pile-supported bridge pier under frozen and thawed soil conditions.The effect of a seasonally frozen soil layer on the seismic vulnerability of a pile-supported bridge pier was evaluated based on reliability theory.Although the frozen soil layer inhibited the seismic response of the ground surface to a certain extent,it exacerbated the acceleration response at the bridge pier top owing to the low radiation damping effect of the frozen soil layer.Furthermore,the frozen soil layer reduced the lateral displacement of the bridge pier top relative to the ground surface by approximately 80%,thereby preventing damage caused by earthquakes,such as falling girders.Compared to the thawed state of the ground surface,the bending moment of the bridge pier in frozen ground increases.However,the bending moment of the pile foundation in frozen ground decreases,thereby lessening the seismic vulnerability of the bridge pile foundation.The results of this can provide a reference for the seismic response analysis and seismic risk assessment of pile-supported bridges in seasonally frozen regions.
基金supported by the Taishan Scholar Project(No.ts20190991,tsqn202211378)the Key R&D Project of Shandong Province(No.2022CXPT023)the General Program of National Natural Science Foundation of China(No.82371933)。
文摘Objective:This study aims to develop a deep multiscale image learning system(DMILS)to differentiate malignant from benign thyroid follicular neoplasms on multiscale whole-slide images(WSIs)of intraoperative frozen pathological images.Methods:A total of 1,213 patients were divided into training and validation sets,an internal test set,a pooled external test set,and a pooled prospective test set at three centers.DMILS was constructed using a deep learningbased weakly supervised method based on multiscale WSIs at 10×,20×,and 40×magnifications.The performance of the DMILS was compared with that of a single magnification and validated in two pathologist-unidentified subsets.Results:The DMILS yielded good performance,with areas under the receiver operating characteristic curves(AUCs)of 0.848,0.857,0.810,and 0.787 in the training and validation sets,internal test set,pooled external test set,and pooled prospective test set,respectively.The AUC of the DMILS was higher than that of a single magnification,with 0.788 of 10×,0.824 of 20×,and 0.775 of 40×in the internal test set.Moreover,DMILS yielded satisfactory performance on the two pathologist-unidentified subsets.Furthermore,the most indicative region predicted by DMILS is the follicular epithelium.Conclusions:DMILS has good performance in differentiating thyroid follicular neoplasms on multiscale WSIs of intraoperative frozen pathological images.
基金support provided by the Open Project Foundation for Key Laboratories of Universities in Fujian Province(KF-T18014)the Scientific Research Project of Shaanxi Coalfield Geology Group Co.,Ltd.(SMDZ-2019CX-7).
文摘The artificial ground-freezing method is the main technical means for the excavation of mines and tunnels through the water-rich sand layer,and the comprehensive understanding of the mechanical properties of frozen saturated sand and the stress-strain relationship under complex stress can provide important guidance.In this study,a series of true triaxial tests of frozen saturated sand samples were conducted.Combined with the test data,the effects of temperature and medium principal stress ratio(b)on the strength and deformation characteristics of frozen saturated sand are discussed.In addition,a cohesion tensor is introduced to the Wu-Lin hypoplastic model.A scalar value is used to characterize the effect of temperature on the strength of frozen soil.The defect that the original model cannot describe the tensile capacity of frozen soil under low stress conditions is clearly solved.In addition,the cumulative deformation state variable is introduced to improve the response performance of the model in triaxial compression tests.The hypoplastic model of frozen soil has shown good performance in simulating triaxial compression tests at different temperatures and medium principal stress ratios.
基金The authors express their gratitude to the financial support from National Key R&D Program of China(No.2023YFB2604001)National Natural Science Foundation of China(No.52478475,No.52378463 and No.52168066).
文摘The pile-plate structure has proven highly effective support for high-speed railway subgrades,particularly in poor geological conditions.Although its efficacy in non-frozen regions is well-established,its potential in frozen regions remains underexplored.In seasonally frozen areas,F-T(freeze-thaw)cycles threaten subgrade stability,necessitating research on pile-plate structure’s behavior under such conditions.To address this challenge,a scaled model experiment was conducted on a silty sand foundation,simulating F-T cycles using temperature control devices.Key parameters,including soil temperature,frozen depth,and displacement,were systematically monitored.Results indicate that the bearing plate functions as an effective insulation layer,significantly reducing sub-zero temperature penetration.Additionally,the anchoring action of the piles mitigates frost heave in the foundation soil,while the plate middle restrains soil deformation more effectively due to increased constraint.The thermal insulation provided by the plate maintains higher soil temperatures,delaying the onset of freezing.By the end of each freezing stage,the vertical displacement in the natural subgrade is approximately 4 times greater than that beneath the pile-plate structure.Furthermore,the frost depth is about 1.3-1.4 times and 1.6-4.9 times greater than that measured below the plate edge and middle,respectively.These insights contribute to the development of more resilient designs for high-speed railway subgrades in seasonally frozen regions,offering engineers a robust,scientifically-backed foundation for future infrastructure projects.
基金Dalian Jiaotong University for its support during this research。
文摘To ensure the safe operation of trains in seasonally frozen regions, achieving accurate and interpretable displacement prediction of tunnel portal slopes is a fundamental requirement. In this paper, we developed a hybrid prediction model that integrates dual signal decomposition with an interpretable deep neural network. The Complete Ensemble Empirical Mode Decomposition with Adaptive Noise(CEEMDAN) first decomposes the original signals, then performs mode selection and reconstruction based on sample entropy and clustering to suppress redundancy. The high-frequency components are further analyzed using VMD and optimized via DLABC, thereby enhancing multi-scale dynamic feature extraction. On this basis, a Convolutional Neural Network(CNN)-Long Short-Term Memory(LSTM)-Attention model, tuned by the Dung Beetle Optimizer(DBO), is constructed to jointly capture local features, temporal dependencies, and key time-specific responses. Results show the proposed model achieves R^(2)>0.99 and MSE<0.07 across multiple monitoring points, significantly outperforming single-decomposition models(e.g., VMD-BP, R^(2)=0.896, MSE=1.700). The dual decomposition strategy proves effective in noise suppression and feature enhancement. Additionally, the SHapley Additive ex Planations(SHAP) analysis visualizes the model's decision process, quantifying the contribution of key factors to slope deformation, thus improving transparency and reliability. The model demonstrates specific adaptability to freeze-thaw environments, providing a robust framework for forecasting slope deformation and issuing early warnings in seasonally frozen regions.
文摘Objective To assess the efficacy and possible adverse effects of acupuncture on frozen shoulder. Methods Based on the key words, i.e. acupuncture, electroacupuncture, acupuncture-moxibustion, frozen shoulder, adhesive capsulitis, shoulder disorders etc., the Chinese databases were retrieved, including Oochrane Musculoskeleta Group, Oochrane Controlled Trials Register, Oochrane Complementary Medicine Field, and the central database of the Oochrane Library as well as MEDLINE, EMBASE and Chinese Biomedical CD （OBM-disc）. 20 Chinese medical journals and relevant academic conference proceedings have been searched manually. The reference lists of identified documents were checked as the supplementary retrieval. Results 6 randomized controlled trials on frozen shoulder with acupuncture and electroacupuncture were included, indicating quite advanced study quality. There were 34 to 257 participants in the trials, 668 in total. The total OR of CMS/OSA was OR 3.49 （95 % CI - 2.64 to 9.63）, the total OR of VAS was OR - 1.24 （95% CI -3.50 to 1.01）, the total OR of ROM was OR 35.70 （95% CI 22.91 to 48.49）; the total OR of MELLE was OR 4.30 （95% OI 2.32 to 7.98）. Conclusion It is shown in the present limited inclusive trials on frozen shoulder that acupuncture is the safe therapy and effective on improving the global function, relieving pain, and improving the range of motion of shoulder. All the therapeutic effects of acupuncture are superior to those in control group. However, much more high quality trials are required to provide much stronger evidence. Additionally, much more evidences on validity of frozen shoulder with other assessing indexes involved are required in the treatment with acupuncture.
基金Supported by key project of Zhejiang Administra on of Tradi onal Chinese Medicine: 2007 ZA 011
文摘Objective To explore better therapies for the treatment of frozen shoulder. Methods One hundred and seventy-four cases were divided into a filiform needle group （56 cases）, an electroacupuncture group （57 cases） and a warming needle group （61 cases） according to the randomized, controlled and single-blind study principles. Jiānqián （肩前 Extra）, Jiānyú （肩髃 LI 15）, Jiānliáo （肩髎 TE 14）, Nàoshū （臑俞 SI 10）, Wàiguān （外关 TE 5）, Hégǔ （合谷 LI 4） were used in all three groups but treated with filiform needle, electroacupuncture and warming needle technique respectively. The needles were retained for 30 min. It was given once every other day and 5 times constituted as one course. Pain indices and activity degree of shoulders were measured and recorded before and after treatment every time. Results The total effective rate was 93.0% （53/57） in the electroacupuncture group and 95.1% （58/61） in the warming needle group, both superior to that of 78.6% （44/56） in the filiform needle group （both P〈0.01）, but there was no significant difference between electroacupuncture group and warming needle group （P〉0.05）. After one course of treatment, the decline indices of shoulder pain of electroacupuncture group （4.28±0.22） and warming needle group （3.74±0.17） were both significantly greater than that of filiform needle group （2.78±0.18）（both P〈0.01）. And the decline indices of electroacupuncture group was also greater than that of warming needle group （P〈0.05）. The improvements of shoulder activity degree of warming needle group （76.92±5.53） and electroacupuncture group （60.37±3.80） were both greater than that of filiform needle group （42.50±3.67） （both P〈0.01）. And shoulder activity degree of warming needle group was also greater than that of electroacupuncture group （P〈0.01）. After one course of treatment, improvement of shoulder activity degree and decline indices of shoulder pain in these three groups were better than that after the first time treatment （all P〈0.01）. Conclusion All these three acupuncture therapies can achieve good therapeutic effects for frozen shoulder. The therapeutic effects of electroacupuncture and warming needle groups are superior to that of filiform needle group. All these three therapies could significantly reduce patients’ pain and improve their shoulder activity degree. The analgesic effect of electroacupuncture is the best, and the shoulder activity degree improved by warming needle is the best. The improvement of clinical therapeutic effect mainly depends on the therapy and the treatment times when the same acupoints are selected and the condition of illness are similar.
基金supported by the National Natural Science Foundation of China (No.41271080 and No.41230630)the Western Project Program of the Chinese Academy of Sciences(KZCX2-XB3-19)the open fund of Qinghai Research and Observation Base, Key Laboratory of Highway Construction and Maintenance Technology in Permafrost Region Ministry of Transport, PRC (2012-12-4)
文摘To study the influence of temperature and water content on ultrasonic wave velocity and to establish the relationship between ultrasonic wave velocity and frozen silty clay strength, ultrasonic tests were conducted to frozen silty clay by using RSM-SY5（T） nonmetal supersonic test meter, and the tensile strength and compressive strength of silty clay were measured under various negative temperatures. Test and analysis results indicate that, ultrasonic wave velocity rapidly changes in the temperature range of-1 ℃ to -5 ℃. Ultrasonic wave velocity increased with an increase of water content until the water content reached the critical water content, while decreased with an increase of water content after the water content exceeded the critical water content. This study showed that there was strong positive correlation between the ul- trasonic wave velocity and the frozen soil strength. As ultrasonic wave velocity increased, either tensile strength or com- pressive strength increased. Based on the experimental data, the relationship between ultrasonic wave velocity and frozen silty clay strength was obtained through regression analysis. It was found that the ultrasonic test technique can be used to test frozen soils and lay the foundation for the determination of frozen soil strength.
基金the National Natural Science Foundation of China(Grant No.41702334).
文摘Determining the mechanical properties of frozen rock is highly important in cold-area engineering.These properties are essentially correlated with the content of liquid water remaining in frozen rock.Therefore,accurate determination of unfrozen water content could allow rapid evaluation of mechanical properties of frozen rock.This paper investigates the hysteresis characteristics of ultrasonic waves applied to sandstone(in terms of the parameters of P-wave velocity,amplitude,dominant frequency and quality factor Q)and their relationships with unfrozen water content during the freeze-thaw process.Their correlations are analysed in terms of their potential for use as indicators of freezing state and unfrozen water content.The results show that:(1)During a freeze-thaw cycle,the ultrasonic parameters and unfrozen water content of sandstone have significant hysteresis with changes in temperature.(2)There are three clear stages of change during freezing:supercooled stage(0℃to-2℃),rapid freezing stage(-2℃to-3℃),and stable freezing stage(-3℃to-20℃).The changes in unfrozen water content and ultrasonic parameters with freezing temperature are inverse.(3)During a single freeze-thaw cycle,the ultrasonic parameters of sandstone are significantly correlated with its unfrozen water content,and this correlation is affected by the pore structure.For sandstones with mesopores greater than 50%,there are inflection points in the curves of ultrasonic parameters vs.unfrozen water content at-3℃during freezing and at-1℃during thawing.It was found that thermal deformation of the mineral-grain skeleton and variations in the phase composition of pore water change the propagation path of ultrasonic waves.The inflection point in the curve of dominant frequency vs.temperature clearly marks the end of the rapid freezing stage of pore water,in which more than 70%of the pore water freezes.Consequently,the dominant frequency can be used as an index to conveniently estimate the unfrozen water content of frozen rock and,hence,its mechanical properties.
基金We acknowledge the funding support from the National Natural Science Foundation of China(Grant No.42271148).
文摘Due to the presence of ice and unfrozen water in pores of frozen rock,the rock fracture behaviors are susceptible to temperature.In this study,the potential thawing-induced softening effects on the fracture behaviors of frozen rock is evaluated by testing the tension fracture toughness(KIC)of frozen rock at different temperatures(i.e.-20℃,-15℃,-12℃,-10℃,-8℃,-6℃,-4℃,-2℃,and 0℃).Acoustic emission(AE)and digital image correlation(DIC)methods are utilized to analyze the microcrack propagation during fracturing.The melting of pore ice is measured using nuclear magnetic resonance(NMR)method.The results indicate that:(1)The KIC of frozen rock decreases moderately between-20℃ and-4℃,and rapidly between-4℃ and 0℃.(2)At-20℃ to-4℃,the fracturing process,deduced from the DIC results at the notch tip,exhibits three stages:elastic deformation,microcrack propagation and microcrack coalescence.However,at-4℃e0℃,only the latter two stages are observed.(3)At-4℃e0℃,the AE activities during fracturing are less than that at-20℃ to-4℃,while more small events are reported.(4)The NMR results demonstrate a reverse variation trend in pore ice content with increasing temperature,that is,a moderate decrease is followed by a sharp decrease and-4℃ is exactly the critical temperature.Next,we interpret the thawing-induced softening effect by linking the evolution in microscopic structure of frozen rock with its macroscopic fracture behaviors as follow:from-20℃ to-4℃,the thickening of the unfrozen water film diminishes the cementation strength between ice and rock skeleton,leading to the decrease in fracture parameters.From-4℃ to 0℃,the cementation effect of ice almost vanishes,and the filling effect of pore ice is reduced significantly,which facilitates microcrack propagation and thus the easier fracture of frozen rocks.
基金This work was supported by the National Key R&D Program of(Grant No.2016YFA0602302).
文摘The acquisition of spatial-temporal information of frozen soil is fundamental for the study of frozen soil dynamics and its feedback to climate change in cold regions.With advancement of remote sensing and better understanding of frozen soil dynamics,discrimination of freeze and thaw status of surface soil based on passive microwave remote sensing and numerical simulation of frozen soil processes under water and heat transfer principles provides valuable means for regional and global frozen soil dynamic monitoring and systematic spatial-temporal responses to global change.However,as an important data source of frozen soil processes,remotely sensed information has not yet been fully utilized in the numerical simulation of frozen soil processes.Although great progress has been made in remote sensing and frozen soil physics,yet few frozen soil research has been done on the application of remotely sensed information in association with the numerical model for frozen soil process studies.In the present study,a distributed numerical model for frozen soil dynamic studies based on coupled water-heat transferring theory in association with remotely sensed frozen soil datasets was developed.In order to reduce the uncertainty of the simulation,the remotely sensed frozen soil information was used to monitor and modify relevant parameters in the process of model simulation.The remotely sensed information and numerically simulated spatial-temporal frozen soil processes were validated by in-situ field observations in cold regions near the town of Naqu on the East-Central Tibetan Plateau.The results suggest that the overall accuracy of the algorithm for discriminating freeze and thaw status of surface soil based on passive microwave remote sensing was more than 95%.These results provided an accurate initial freeze and thaw status of surface soil for coupling and calibrating the numerical model of this study.The numerically simulated frozen soil processes demonstrated good performance of the distributed numerical model based on the coupled water-heat transferring theory.The relatively larger uncertainties of the numerical model were found in alternating periods between freezing and thawing of surface soil.The average accuracy increased by about 5%after integrating remotely sensed information on the surface soil.The simulation accuracy was significantly improved,especially in transition periods between freezing and thawing of the surface soil.
基金financially supported by the National Basic Research Program of China (No. 2013CBA01803)the National Natural Science Foundation of China (No. 41101065)and the CAS "Equipment Development Project for Scientific Research" (No. YZ201523)
文摘Adopting the quasi-three-dimensional （Quasi-3D） numerical method to optimize the anti-freeze design parameters of an underground pipeline usually involves heavy numerical calculations. Here, the fitting formulae between the safe con-veyance distance （SCD） of a water pipeline and six influencing factors are established based on the lowest water temper-ature （LWT） along the pipeline axis direction. With reference to the current widely used anti-freeze design approaches for underground pipelines in seasonally frozen areas, this paper first analyzes the feasibility of applying the maximum frozen penetration （MFP） instead of the mean annual ground surface temperature （MAGST） and soil water content （SWC） to calculate the SCD. The results show that the SCD depends on the buried depth if the MFP is fixed and the variation of the MAGST and SWC combination does not significantly change the SCD. A comprehensive formula for the SCD is estab-lished based on the relationships between the SCD and several primary influencing factors and the interaction among them. This formula involves five easy-to-access parameters： the MFP, buried depth, pipeline diameter, flow velocity, and inlet water temperature. A comparison between the analytical method and the numerical results based on the Quasi-3D method indicates that the two methods are in good agreement overall. The analytic method can be used to optimize the anti-freeze design parameters of underground water pipelines in seasonally frozen areas under the condition of a 1.5 safety coefficient.
基金supported by the National Natural Science Foundation of China (No. 41271080)the National Basic Research Program ("973") of China (No. 2012CB026102)the Western Project Program of the Chinese Academy of Sciences (No. KZCX2-XB3-19)
文摘Ultrasonic P-wave tests of frozen silt and frozen sand were conducted during uniaxial loading by using an RSM^-SY5（T） nonmetal ultrasonic test meter to study the velocity characteristics of P-waves. The experimental results indicate that the P-wave velocity is affected by soil materials, temperature, and external loads, so the P-wave velocity is different in frozen silt and frozen sand, but all decrease with an increase of temperature and increase at first and then decrease with strain during the loading process. There is an exponential relationship between uniaxial compressive strength and P-wave ve- locity, and the correlation between them is very good. The characteristic parameters of acoustic waves can, to some extent, reflect the development of internal cracks in frozen soils during loading.
基金supported by the National Natural Science Foundation of China(Grant No.41971086)Natural Science Foundation of Shanxi Province(Grant No.2023-JC-QN-0626,2022JQ-467).
文摘In permafrost regions with warm frozen soil,subgrade thaw-collapse phenomenon commonly occurs,facing thaw collapse problems of the existed frozen soil subgrade,thus it is difficult to use traditional methods such as active cooling and passive protection technology to stabilize the existed warm frozen soil subgrade.This study derives a novel stabilizer method,a long-short(L-S)cement-mixed batter pile composite foundation to stabilize the existed warm frozen soil subgrade.To solve the thawcollapse problems in warm frozen soil subgrade,high water content and large compressibility characteristics were compared between soft soil and warm frozen soils.Theoretical analysis of heat conduction and numerical simulation of finite element model were used to study the freeze–thaw process and evaluate the stabilized effects of the L-S cement-mixed batter piles on the warm frozen soil foundation of the Qinghai-Xizang Highway.Furthermore,the thaw process and mechanical properties of foundation and piles were analyzed by introducing the hydration heat factor in the thermodynamic control equation.The results indicate that the thawing displacement of the existed warm frozen soil subgrade was reduced owing to the“support”and“grasp”effects of the L-S cement-mixed batter piles on the surrounding soil.The composite ground formed by strengthening the warm frozen ground with batter piles could considerably improve the bearing capacity of the existed warm frozen ground,effectively restrain the deformation of the upper embankment,and improve the strength of the ground.The analysis can provide method for the construction design of cement mixing batter pile foundation in cold regions.
基金National Natural Science Foundation grant project(41572270)
文摘In this study, frozen red sandstone specimens were impacted by a Split Hopkinson bar (SHPB), with a velocity of 4.558 ~ 6.823 ms-1. The temperature of the specimens was maintained at -15℃ during the experiment. For comparison purposes, static uniaxial compression tests were conducted in advance using a freezing triaxial test machine. Four stress-strain curves were obtained in diff erent average strain rates. The test results suggested that when the average strain rate is low, the specimen strength changes gradually;but when it is high, its strength changes rapidly. When the average strain rate is 120.73 s-1, the peak value of stress is as high as 82.96 MPa, which is about two times that of the static compressive strength of 44.1 MPa. A constitutive model was established that was composed of the damaged, viscoelastic and spring bodies, and revealed the variations of compressive strength and strain for the frozen red sandstone under diff erent high strain rates. The test results also showed that the failure form was correlated to the average strain rate of the frozen red sandstone. When the average strain rate is low, the damage was only distributed on the specimen’s edges. However, as the average strain rate increases, the damage range extended to the central parts of the specimen. When the average strain rate reached 107.34s-1, the specimen was smashed.
