Tunnel-type anchorages(TTAs)installed in human gathering areas are characterized by a shallow burial depth,and in many instances,they utilize soft rock as the bearing stratum.However,the stability control measures and...Tunnel-type anchorages(TTAs)installed in human gathering areas are characterized by a shallow burial depth,and in many instances,they utilize soft rock as the bearing stratum.However,the stability control measures and the principle of shallow TTAs in soft rock have not been fully studied.Hence,a structure suitable for improving the stability of shallow TTAs in soft rock strata,named the anti-pull tie(APT),was added to the floor of the back face.Physical tests and numerical models were established to study the influence of the APT on the load transfer of TTAs,the mechanical response of the surrounding rock,the stress distribution of the interface,and the failure model.The mechanical characteristics of APTs were also studied.The results show that the ultimate bearing capacity of TTAs with an APT is increased by approximately 11.8%,as compared to the TTAs without an APT.Also,the bearing capacity of TTAs increases approximately linearly with increasing height,width,length,and quantity of APTs,and decreases approximately linearly with increasing distance from the back face and slope angle of the tie slope.The normal squeezing between the tie slope and the surrounding rock increases the shear resistance of the interface and expands the range of the surrounding rock participating in bearing sharing.Both tension and compression zones exist in the APT during loading.The tension zone extends from the tie toe to the tie bottom along the tie slope.The range of the tie body tension zone constantly expands to the deep part of the APT with an increasing load.The peak tensile stress value is located at the tie toe.The distribution of compressive stress in the tie body is the largest at the tie top,followed by the tie slope,and then the tie bottom.展开更多
The shear performance of bolts plays a crucial role in controlling rock mass stability,and the roughness of the joint surface is one of the main factors affecting the mechanical properties of anchored joints.The 2nd g...The shear performance of bolts plays a crucial role in controlling rock mass stability,and the roughness of the joint surface is one of the main factors affecting the mechanical properties of anchored joints.The 2nd generation of negative Poisson ratio(2G-NPR)bolt is a new independently developed material characterized by high strength and toughness.However,the influence of joint surface roughness on its anchorage shear performance remains unexplored.This study involves preparing regular saw-tooth jointed rock masses and conducting laboratory shear comparison tests on unbolted samples,2G-NPR bolts,and Q235 steel anchors.A three-dimensional finite element method,developed by the author,was employed for numerical simulations to analyze the influence of saw-tooth angles on the shear resistance of anchored bolts.The findings show that the anchorage of bolts enhances the shear strength and deformation of saw-tooth rock joints.The 2G-NPR bolts demonstrate superior performance in shear strength and deformation enhancement compared to Q235 steel anchors,including improved toughening and crack-arresting effects.Furthermore,the improvement of the shear strength and displacement of the bolt decreases with the increase of the joint saw-tooth angle.These findings provide a valuable test basis for the engineering application of 2G-NPR bolts in rock mass stabilization.展开更多
Understanding the anchorage performance of en-echelon joints under cyclic shear loading is crucial for optimizing support strategies in jointed rock masses.This study examines the anchorage effects on enechelon joints...Understanding the anchorage performance of en-echelon joints under cyclic shear loading is crucial for optimizing support strategies in jointed rock masses.This study examines the anchorage effects on enechelon joints with various orientations using laboratory cyclic shear tests.By comparing unbolted and bolted en-echelon joints,we analyze shear zone damage,shear properties,dilatancy,energy absorption,and acoustic emission characteristics to evaluate anchoring effects across shear cycles and joint orientations.Results reveal that bolted en-echelon joints experience more severe shear zone damage after cycles,with bolt deformation correlating to shear zone width.Bolted en-echelon joints exhibit faster shear strength deterioration and higher cumulative strength loss compared to unbolted ones,with losses ranging from 20.04%to 72.76%.The compressibility of en-echelon joints reduces the anchoring effect during shear cycles,leading to lower shear strength of bolted en-echelon joints in later stages of shear cycles compared to unbolted ones.Bolts reinforce en-echelon joints more effectively at non-positive angles,with the best performance observed at 0°and-60°.Anchorage accelerates the transition from rolling friction to sliding friction in the shear zone,enhancing energy absorption,which is crucial for rock projects under dynamic shear loading.Additionally,rock bolts expedite the transition of the cumulative AE hits and cumulative AE energy curves from rapid to steady growth,indicating that strong bolt-rock interactions accelerate crack initiation,propagation,and energy release.展开更多
In underground engineering with complex conditions,the bolt(cable)anchorage support system is in an environment where static and dynamic stresses coexist,under the action of geological conditions such as high stresses...In underground engineering with complex conditions,the bolt(cable)anchorage support system is in an environment where static and dynamic stresses coexist,under the action of geological conditions such as high stresses and strong disturbances and construction conditions such as the application of high prestress.It is essential to study the support components performance under dynamic-static coupling conditions.Based on this,a multi-functional anchorage support dynamic-static coupling performance test system(MAC system)is developed,which can achieve 7 types of testing functions,including single component performance,anchored net performance,anchored rock performance and so on.The bolt and cable mechanical tests are conducted by MAC system under different prestress levels.The results showed that compared to the non-prestress condition,the impact resistance performance of prestressed bolts(cables)is significantly reduced.In the prestress range of 50–160 k N,the maximum reduction rate of impact energy resisted by different types of bolts is 53.9%–61.5%compared to non-prestress condition.In the prestress range of 150–300 k N,the impact energy resisted by high-strength cable is reduced by76.8%–84.6%compared to non-prestress condition.The MAC system achieves dynamic-static coupling performance test,which provide an effective means for the design of anchorage support system.展开更多
During orthodontic treatment,we can achieve differential movements by using photobiomodulation(PBM)as an adjuvant before applying force.We can expect a greater bone density that initially resists movement while applyi...During orthodontic treatment,we can achieve differential movements by using photobiomodulation(PBM)as an adjuvant before applying force.We can expect a greater bone density that initially resists movement while applying PBM to the other teeth to achieve an accelerating effect.The proposed protocol is to use an 810 nm laser at 0.1W power,applying between 4 and 6J per tooth for 22 s on the vestibular and lingual root surfaces,following the axial axis of the tooth.The energy density depends on the tip selected in the instrument.Normal bone remodeling cannot be avoided by applying high doses of PBM.PBM should be applied before orthodontic force to reduce tooth movement.In addition,PBM can be used during force application to teeth that require acceleration to achieve differential movement in orthodontic treatments.The protocol is the same in both scenarios.展开更多
In order to investigate the failure mechanism of the reinforced muddy soft rock under the influence of the hydration reaction when ground water is present,a series of confined compressive tests and Acoustic Emission(A...In order to investigate the failure mechanism of the reinforced muddy soft rock under the influence of the hydration reaction when ground water is present,a series of confined compressive tests and Acoustic Emission(AE)recordings were conducted subject to various moisture content levels and lateral confining stresses.It was found that the failure modes of the reinforced rock specimen were affected by the moisture content level and the lateral stress σ_(2) in a way that the load bearing capacity of the reinforced rock would increase with the lateral stress σ_(2) but decrease as the moisture content increased.An increase in the moisture content would reduce the extent of the influence of the lateral stress on the load bearing capacity of the reinforced rock.In addition,much less AE counts were recorded when the moisture content increased indicating that the crack initiation and propagation in this case was easier due to the reduction of the required external input energy.With increasing moisture content,the failure mode of the specimen gradually changes from sudden and brittle to progressive and ductile.Moreover,the hydration reaction became more significant leading to a complete debonding between the grout and the rock.Consequently,the reinforcement provided by the rock bolt to the rock became negligible.展开更多
An anchorage reliability analysis approach for simply supported reinforced concrete beams under corrosion attack in the anchorage zone is developed.The first-order second-moment method is employed to analyze the effec...An anchorage reliability analysis approach for simply supported reinforced concrete beams under corrosion attack in the anchorage zone is developed.The first-order second-moment method is employed to analyze the effects of various factors on the anchorage reliability.These factors include both the length and width of cover cracking due to reinforcement corrosion,the cover thickness,the anchorage length,and the stirrup ratio.The results show that the effect of corrosion-induced crack length on the reliability index for anchorage,β0,is negligible when the crack on the concrete surface is just appearing,but with the crack widening,the β0 value is reduced significantly;the considerable changes in β0 result from a variation in cover depth and anchorage length;the effect of changes in the diameter or space of stirrups on the anchorage resistance is very limited,and the variation in β0 is also very low.展开更多
The complex tunnelling constructive environment in urban area in similar green field situations is faced through analytical evaluations in order to control the design calculation process and subsequently manage the in...The complex tunnelling constructive environment in urban area in similar green field situations is faced through analytical evaluations in order to control the design calculation process and subsequently manage the interventions techniques with the aim of totally reducing the typical settlements trough above the tunnel either during the construction stage or during the serviceability stage. Recently, the author has proposed an operative and mathematical method by an opportune choice of tensioned anchors to control the tunnel lining settlements. In order to completely eliminate the remainder typical soft soil trough which is normal to the line of the tunnel, it is here proposed to use and properly calculate the interventions of stone columns by the SAVE （silent, advanced, vibration-erasing） Compozer method, in combination with the anchorages.展开更多
This paper investigated the stress evolution,displacement field,local deformation and its overall distribution,and failure characteristics of the anchorage structure of surrounding rock with different rockbolt spacing...This paper investigated the stress evolution,displacement field,local deformation and its overall distribution,and failure characteristics of the anchorage structure of surrounding rock with different rockbolt spacing through the model experiments.The influences of the pre-tightening force and spacing of rockbolt on the support strength of the anchorage structure of surrounding rock were analyzed by the simulation using FLAC3D numerical software.The support scheme of the excavated roadway was then designed,and the effectiveness of this support scheme was further verified by the displacement measurement of the roadway.The results showed that the maximum displacement between the roof and floor of the west wing track roadway in Kouzidong coal mine,China is about 42 mm,and the maximum displacement between its both sides is about 72 mm,indicating that the support scheme proposed in this study can ensure the stability and safety of the excavated roadway.展开更多
It is important to quantify the effect of the root diameter, the embedment length of the root and load speed on the soil-root interface mechanical properties for studying the root anchorage. The soilroot interface mec...It is important to quantify the effect of the root diameter, the embedment length of the root and load speed on the soil-root interface mechanical properties for studying the root anchorage. The soilroot interface mechanical properties can be obtained through the pullout force and root slippage curve(F-S curve). About 120 Pinus tabulaeformis single roots whose diameters ranged from 1 mm to 10 mm divided into 6 groups based on different root embedment length(50 mm, 100 mm and 150 mm) and different load velocity(10 mm·min^(-1), 50 mm·min^(-1), 100 mm·min^(-1) and 300 mm·min^(-1)) were investigated using the pullout method. This study aims to explore the mechanical properties of the soil-root interface in the real conditions using the pullout test method. The results showed two kinds of pullout test failure modes during the experimental process: breakage failure and pullout failure. The results showed that the roots were easier to be broken when the root diameter was smaller or the loading speed was larger. The relationship between the maximum anchorage force and root diameter was linear and the linearly dependent coefficient(R^2) was larger than 0.85. The anchorage force increased with the root embedment length. An increase of 10%^(-1)5% for the maximumanchorage force was found when load speed increased from 10 to 300 mm.min^(-1). The mean peak slippage of the root was from 13.81 to 35.79 mm when the load velocity varied from 10 to 300 mm.min^(-1). The study will be helpful for the design of slopes reinforced by vegetation and in predicting risk of uprooting of trees, and will have practical benefits for understanding the mechanism of landslide.展开更多
Based on the fact that the shear stress along anchorage segment is neither linearly nor uniformly distributed, the load transfer mechanism of the tension type anchor was studied and the mechanical characteristic of an...Based on the fact that the shear stress along anchorage segment is neither linearly nor uniformly distributed, the load transfer mechanism of the tension type anchor was studied and the mechanical characteristic of anchorage segment was analyzed. Shear stress?strain relationship of soil surrounding anchorage body was simplified into three-folding-lines model consisting of elastic phase, elasto-plastic phase and residual phase considering its softening characteristic. Meanwhile, shear displacement method that has been extensively used in the analysis of pile foundation was introduced. Based on elasto-plastic theory, the distributions of displacement, shear stress and axial force along the anchorage segment of tension type anchor were obtained, and the formula for calculating the elastic limit load was also developed accordingly. Finally, an example was given to discuss the variation of stress and displacement in the anchorage segment with the loads exerted on the anchor, and a program was worked out to calculate the anchor maximum bearing capacity. The influence of some parameters on the anchor bearing capacity was discussed, and effective anchorage length was obtained simultaneously. The results show that the shear stress first increases and then decreases and finally trends to the residual strength with increase of distance from bottom of the anchorage body, the displacement increases all the time with the increase of distance from bottom of the anchorage body, and the increase of velocity gradually becomes greater.展开更多
The stability of the anchorage slope on the Baiyang Yangtze River Highway Bridge in Yichang,China,was investigated under different rainfall conditions using model test,numerical simulation,and factor analysis.The resu...The stability of the anchorage slope on the Baiyang Yangtze River Highway Bridge in Yichang,China,was investigated under different rainfall conditions using model test,numerical simulation,and factor analysis.The results of the study are as follows:(1)with the increase of rainfall intensity,the change of earth pressure can be divided into three stages.However,when the rainfall intensity was larger than a certain value,the change of earth pressure of cut slope became two stages;with the increase of rainfall intensity,pore water pressure increased with the increase of rainfall time,while at a certain stage after the rainfall,the pore water pressure in the cut slope did not decrease immediately,but increased for a period of time.(2)When the rainfall stopped,the stability coefficient of the anchorage slope continued to decrease,then slowly increased,and finally tended to be gentle.Meanwhile,when the rainstorm reached a certain intensity,the main factor that restricted the rainfall infiltration rate became the geotechnical permeability coefficient of the cut slope,which was no longer the rainfall intensity.(3)Factor analysis shows that the rainfall intensity and rainfall duration were the most important factors for anchorage slope stability,while earth pressure,pore water pressure and slope displacement were much less significant.展开更多
With the help of plant roots, slope vegetation makes the slope soil mass become a composite material of soil and roots, and thus enhances shear strength of the slope soil mass and stability of the slope. However, the ...With the help of plant roots, slope vegetation makes the slope soil mass become a composite material of soil and roots, and thus enhances shear strength of the slope soil mass and stability of the slope. However, the related studies at present are still qualitative. In this paper, quantitative analysis of the interaction between roots and soil mass are made. By the analysis of the interaction between herbaceous plant roots including lateral roots of woody plants and rock and soil mass, a mechanical model of the interaction between frictional roots and soil is established, and its correctness is shown. A mechanical model of the interaction between anchorage root, namely, woody plant taproot, and soil is also established. The establishment of the models provides a useful means in quantitative analysis of the interaction between plant roots and soil, and has practical values.展开更多
Anchoring mechanism and failure characteristics of composite soft rock with weak interface usually exhibit remarkable difference from those in single rock mass.In order to fully understand the reinforcement mechanism ...Anchoring mechanism and failure characteristics of composite soft rock with weak interface usually exhibit remarkable difference from those in single rock mass.In order to fully understand the reinforcement mechanism of composite soft roof in western mining area of China,a mechanical model of composite soft rock with weak interface and rock bolt which considering the transverse shear sliding between different rock layers was established firstly.The anchoring effect was quantified by a factor defined as anchoring effect coefficient and its evolution equation was further deduced based on the deformation relationship and homogenized distribution assumption of stress acting on composite structure.Meanwhile,the numerical simulation model of composite soft rock with shear joint was prompted by finite element method.Then detailed analysis were carried out for the deformation features,stress distribution and failure behavior of rock mass and rock bolt near the joint under transverse load.The theoretical result indicates that the anchoring effect of rock-bolt through weak joint changes with the working status of rock mass and closely relates with the physical and geometric parameters of rock mass and rock bolt.From the numerical results,the bending deformation of rock bolt accurately characterized by Doseresp model is mainly concentrated between two plastic hinges near the shear joint.The maximum tensile and compression stresses distribute in the plastic hinge.However,the maximum shear stress appears at the positions of joint surface.The failure zones of composite rock are produced firstly at the joint surface due to the reaction of rock bolt.The above results laid a theoretical and computational foundation for further study of anchorage failure in composite soft rock.展开更多
Based on some assumptions, the dynamic analysis model of anchorage system is established. The dynamic governing equation is expressed as finite difference format and programmed by using MATLAB language. Compared with ...Based on some assumptions, the dynamic analysis model of anchorage system is established. The dynamic governing equation is expressed as finite difference format and programmed by using MATLAB language. Compared with theoretical method, the finite difference method has been verified to be feasible by a case study. It is found that under seismic loading, the dynamic response of anchorage system is synchronously fluctuated with the seismic vibration. The change of displacement amplitude of material points is slight, and comparatively speaking, the displacement amplitude of the outside point is a little larger than that of the inside point, which shows amplification effect of surface. While the axial force amplitude transforms considerably from the inside to the outside. It increases first and reaches the peak value in the intersection between the anchoring section and free section, then decreases slowly in the free section. When considering damping effect of anchorage system, the finite difference method can reflect the time attenuation characteristic better, and the calculating result would be safer and more reasonable than the dynamic steady-state theoretical method. What is more, the finite difference method can be applied to the dynamic response analysis of harmonic and seismic random vibration for all kinds of anchor, and hence has a broad application prospect.展开更多
A tunnel-type anchorage(TTA)is one of the main components in suspension bridges:the bearing mechanism is a key problem.Investigating the deformation characteristics,development law,and failure phenomenon of a TTA unde...A tunnel-type anchorage(TTA)is one of the main components in suspension bridges:the bearing mechanism is a key problem.Investigating the deformation characteristics,development law,and failure phenomenon of a TTA under load can provide the theoretical basis for a robust design.Utilizing the TTA of the Jinsha River suspension bridge at Lijiang Shangri-La railway as a prototype,a laboratory model test of the TTA was carried out for three different contact conditions between the anchorage body and the surrounding rock.The stress and deformation distribution law of the anchorage body and its surrounding rock were studied,and the ultimate bearing capacity and failure mode of the TTA were analyzed.The test results show that the compressive stress level is highest at the rear part of the anchorage body.Moving away from the rear portion of the body,the stress decays in a negative exponential function.Based on the load transfer curve,the calculation formula for the shear stress on the contact surface between the anchorage body and the surrounding rock was derived,which shows that the distribution of the shear stress along the axial direction of the anchorage body is not uniform.The distance from the maximum value to the loading surface is approximately 1/3 of the length of the anchorage body,and the stress decreases as the distance from the loading surface increases.Furthermore,the contact condition between the anchorage body and surrounding rock has a great influence on the bearing capacity of the TTA.The increase in the anti-skid tooth ridge and radial anchor bolt can improve the cooperative working capacity of the anchorage body and the surrounding rock,which is approximately 50%higher than that of the flat contact condition.The main function of the anchor bolt is to increase the overall rigidity of the TTA.The contact condition between the anchorage body and the surrounding rock will lead to a change in the failure mode of the TTA.With an increase in the degree of contact,the failure mode will change from shear sliding along the interface to trumpet-shaped inverted cone-shaped failure extending into the surrounding rock.展开更多
A growing number of studies have reported that mini-implants do not remain in exactly the same position during treatment, although they remain stable. The aim of this review was to collect data regarding primary displ...A growing number of studies have reported that mini-implants do not remain in exactly the same position during treatment, although they remain stable. The aim of this review was to collect data regarding primary displacement immediately straight after loading and secondary displacement over time. A systematic review was performed to investigate primary and secondary displacement. The amount and type of displacement were recorded. A total of 27 studies were included. Sixteen in vitro studies or studies using finite element analysis addressed primary displacement, and nine clinical studies and two animal studies addressed secondary displacement. Significant primary displacement was detected （6.4-24.4 μm） for relevant orthodontic forces （0.5-2.5 N）. The mean secondary displacement ranged from 0 to 2.7 mm for entire mini-implants, The maximum values for each clinical study ranged from 1.0 to 4.1 mm for the head, 1.0 to 1.5 for the body and 1,0 to 1.92 mm for the tail part. The most frequent type of movement was controlled tipping or bodily movement. Primary displacement did not reach a clinically significant level. However, clinicians can expect relevant secondary displacement in the direction of force. Consequently, decentralized insertion within the inter-radicular space, away from force direction, might be favourable. More evidence is needed to provide quantitative recommendations.展开更多
The aim of this retrospective study was to quantitatively evaluate the treatment effects of in- trusion of overerupted maxillary molars using miniscrew implant anchorage and to investigate the apical root resorption a...The aim of this retrospective study was to quantitatively evaluate the treatment effects of in- trusion of overerupted maxillary molars using miniscrew implant anchorage and to investigate the apical root resorption after molar intrusion. The subjects included 30 patients whose average ages were 35.5±9.0 years. All patients had received intrusion treatments for overerupted maxillary molars with miniscrew anchorage. There were 38 maxillary first molars and 26 maxillary second molars to be in- truded. Two miniscrews were inserted in the buccal and palatal alveolar bone mesial to the overerupted molar. Force of 100-150 g was applied by the elastic chains between screw head and attachment on each side. Lateral cephalograms and panoramic radiographs taken before and after intrusion were used to evaluate dental changes and root resorption of molars. Only 6 of the 128 miniscrews failed. The first and second molars were significantly intruded by averages of 3.4 mm and 3.1 mm respectively （P〈0.001）. The average intrusion time was more than 6 months. The crown of the molars mesially tilted by averages of 3.1 degrees and 3.3 degrees （P〈0.001） for first and second molars. The amounts of root resorption were 0.2-0.4 mm on average. The intrusion treatment of overerupted molars with miniscrew anchorages could be used as an efficient and reliable method to recover lost restoration space for pros- thesis. Radiographically speaking, root resorption of molars was not clinically significant after applica- tion of intrusive forces of 200 to 300 g.展开更多
Miniscrews offer a reliable alternative for anchorage during orthodontic treatment,particularly for non-cooperative patients or periodontal patients with alveolar bone loss.The study aims at assessing the correlation ...Miniscrews offer a reliable alternative for anchorage during orthodontic treatment,particularly for non-cooperative patients or periodontal patients with alveolar bone loss.The study aims at assessing the correlation of various clinical indicators with the success or failure of miniscrews used for anchorage during orthodontic treatment.Thirty-four consecutive patients with a cumulative total of 82 miniscrews implanted participated in the study.Generalized Estimating Equations were used to assess the correlation of various factors with success rates.The miniscrew was considered the unit of analysis clustered within site and within patient.The overall success rate of miniscrews was 90.2%.For every additional miniscrew used in a patient＇s oral cavity,the success rate was reduced by 67%.Retromandibular triangle and palatal placement and in movable mucosa resulted in lower success rate.The miniscrew length and diameter were found to correlate with success rates.Orthodontic force applied on miniscrews for uprighting purposes showed a lower success rate than that used for retraction.This study revealed that miniscrews present high success rates.The number of miniscrews used per patient,the miniscrew site placement,the soft tissue type of placement,the miniscrew length and diameter as well as the orthodontic force applied on the miniscrew showed significant correlation with success rates.展开更多
The long-term stability of a prestressed anchored slope might be influenced by the durability of the anchorage structure.To understand long-term stability of anchored rock slopes,the research presented herein evaluate...The long-term stability of a prestressed anchored slope might be influenced by the durability of the anchorage structure.To understand long-term stability of anchored rock slopes,the research presented herein evaluated the performance evolution of a prestressed anchored bedding slope system in a corrosive environment by model test.The corrosion process in a prestressed anchor bar was monitored in terms of its open-circuit potential(OCP),corrosion current density(CCD),and electrochemical impedance spectroscopy(EIS).The stability of the prestressed anchored slope was evaluated by monitoring changes in anchorage force and displacements.The experimental results show that prestress and oxygen could reduce the corrosion resistance of the anchor bar,and anchor bars in a chloride-rich environment are very susceptible to corrosion.Prestressed tendons in a corrosive environment suffer a loss of anchorage force,the prestress decreases rapidly after locking,and the rate thereof decreases until stabilising;in the later stage,corrosion leads to the reduction of the cross-sectional area of the steel bar which may cause the reduction in anchorage force again.Anchorage force controls the deformation and stability of the anchored slope,the prestress loss caused by later corrosion may lead to an increased rate of displacement and stability degradation of the prestressed anchored rock slope.展开更多
基金the financial support provided by the National Natural Science Foundation of China(Grant No.42302332)the Special Funding of Chongqing Postdoctoral Research Project(Grant No.2022CQBSHTB2061,2022CQBSHTB1010)+3 种基金the Chongqing Postdoctoral Science Foundation(Grant No.CSTB2022NSCQ-BHX0738,CSTB2023NSCQBHX0223)the China Postdoctoral Science Foundation(Grant No.2023M730432)the Natural Science Foundation of Chongqing(Grant No.CSTB2023NSCQMSX0913,cstc2021jcyj-msxm X0869)the Postdoctoral Science Foundation of Chongqing Jiaotong University(Grant No.F1220105,22JDKJC-A008)。
文摘Tunnel-type anchorages(TTAs)installed in human gathering areas are characterized by a shallow burial depth,and in many instances,they utilize soft rock as the bearing stratum.However,the stability control measures and the principle of shallow TTAs in soft rock have not been fully studied.Hence,a structure suitable for improving the stability of shallow TTAs in soft rock strata,named the anti-pull tie(APT),was added to the floor of the back face.Physical tests and numerical models were established to study the influence of the APT on the load transfer of TTAs,the mechanical response of the surrounding rock,the stress distribution of the interface,and the failure model.The mechanical characteristics of APTs were also studied.The results show that the ultimate bearing capacity of TTAs with an APT is increased by approximately 11.8%,as compared to the TTAs without an APT.Also,the bearing capacity of TTAs increases approximately linearly with increasing height,width,length,and quantity of APTs,and decreases approximately linearly with increasing distance from the back face and slope angle of the tie slope.The normal squeezing between the tie slope and the surrounding rock increases the shear resistance of the interface and expands the range of the surrounding rock participating in bearing sharing.Both tension and compression zones exist in the APT during loading.The tension zone extends from the tie toe to the tie bottom along the tie slope.The range of the tie body tension zone constantly expands to the deep part of the APT with an increasing load.The peak tensile stress value is located at the tie toe.The distribution of compressive stress in the tie body is the largest at the tie top,followed by the tie slope,and then the tie bottom.
基金Project(GZB202405561)supported by the Postdoctoral Fellowship Program of China Postdoctoral Science FoundationProject(42377154)supported by the National Natural Science Foundation of China。
文摘The shear performance of bolts plays a crucial role in controlling rock mass stability,and the roughness of the joint surface is one of the main factors affecting the mechanical properties of anchored joints.The 2nd generation of negative Poisson ratio(2G-NPR)bolt is a new independently developed material characterized by high strength and toughness.However,the influence of joint surface roughness on its anchorage shear performance remains unexplored.This study involves preparing regular saw-tooth jointed rock masses and conducting laboratory shear comparison tests on unbolted samples,2G-NPR bolts,and Q235 steel anchors.A three-dimensional finite element method,developed by the author,was employed for numerical simulations to analyze the influence of saw-tooth angles on the shear resistance of anchored bolts.The findings show that the anchorage of bolts enhances the shear strength and deformation of saw-tooth rock joints.The 2G-NPR bolts demonstrate superior performance in shear strength and deformation enhancement compared to Q235 steel anchors,including improved toughening and crack-arresting effects.Furthermore,the improvement of the shear strength and displacement of the bolt decreases with the increase of the joint saw-tooth angle.These findings provide a valuable test basis for the engineering application of 2G-NPR bolts in rock mass stabilization.
基金financially supported by the National Natural Science Foundation of China (No.42172292)Taishan Scholars Project Special Funding,and Shandong Energy Group (No.SNKJ2022A01-R26)funded by the China Scholarship Council (CSC No.202006220274)。
文摘Understanding the anchorage performance of en-echelon joints under cyclic shear loading is crucial for optimizing support strategies in jointed rock masses.This study examines the anchorage effects on enechelon joints with various orientations using laboratory cyclic shear tests.By comparing unbolted and bolted en-echelon joints,we analyze shear zone damage,shear properties,dilatancy,energy absorption,and acoustic emission characteristics to evaluate anchoring effects across shear cycles and joint orientations.Results reveal that bolted en-echelon joints experience more severe shear zone damage after cycles,with bolt deformation correlating to shear zone width.Bolted en-echelon joints exhibit faster shear strength deterioration and higher cumulative strength loss compared to unbolted ones,with losses ranging from 20.04%to 72.76%.The compressibility of en-echelon joints reduces the anchoring effect during shear cycles,leading to lower shear strength of bolted en-echelon joints in later stages of shear cycles compared to unbolted ones.Bolts reinforce en-echelon joints more effectively at non-positive angles,with the best performance observed at 0°and-60°.Anchorage accelerates the transition from rolling friction to sliding friction in the shear zone,enhancing energy absorption,which is crucial for rock projects under dynamic shear loading.Additionally,rock bolts expedite the transition of the cumulative AE hits and cumulative AE energy curves from rapid to steady growth,indicating that strong bolt-rock interactions accelerate crack initiation,propagation,and energy release.
基金supported by the National Natural Science Foundation of China(Nos.51927807,52074164,42277174,42077267 and 42177130)the Natural Science Foundation of Shandong Province,China(No.ZR2020JQ23)China University of Mining and Technology(Beijing)Top Innovative Talent Cultivation Fund for Doctoral Students(No.BBJ2023048)。
文摘In underground engineering with complex conditions,the bolt(cable)anchorage support system is in an environment where static and dynamic stresses coexist,under the action of geological conditions such as high stresses and strong disturbances and construction conditions such as the application of high prestress.It is essential to study the support components performance under dynamic-static coupling conditions.Based on this,a multi-functional anchorage support dynamic-static coupling performance test system(MAC system)is developed,which can achieve 7 types of testing functions,including single component performance,anchored net performance,anchored rock performance and so on.The bolt and cable mechanical tests are conducted by MAC system under different prestress levels.The results showed that compared to the non-prestress condition,the impact resistance performance of prestressed bolts(cables)is significantly reduced.In the prestress range of 50–160 k N,the maximum reduction rate of impact energy resisted by different types of bolts is 53.9%–61.5%compared to non-prestress condition.In the prestress range of 150–300 k N,the impact energy resisted by high-strength cable is reduced by76.8%–84.6%compared to non-prestress condition.The MAC system achieves dynamic-static coupling performance test,which provide an effective means for the design of anchorage support system.
文摘During orthodontic treatment,we can achieve differential movements by using photobiomodulation(PBM)as an adjuvant before applying force.We can expect a greater bone density that initially resists movement while applying PBM to the other teeth to achieve an accelerating effect.The proposed protocol is to use an 810 nm laser at 0.1W power,applying between 4 and 6J per tooth for 22 s on the vestibular and lingual root surfaces,following the axial axis of the tooth.The energy density depends on the tip selected in the instrument.Normal bone remodeling cannot be avoided by applying high doses of PBM.PBM should be applied before orthodontic force to reduce tooth movement.In addition,PBM can be used during force application to teeth that require acceleration to achieve differential movement in orthodontic treatments.The protocol is the same in both scenarios.
基金financially supported by the National Natural Science Foundation of China(U22A20165,12072102,52174089).
文摘In order to investigate the failure mechanism of the reinforced muddy soft rock under the influence of the hydration reaction when ground water is present,a series of confined compressive tests and Acoustic Emission(AE)recordings were conducted subject to various moisture content levels and lateral confining stresses.It was found that the failure modes of the reinforced rock specimen were affected by the moisture content level and the lateral stress σ_(2) in a way that the load bearing capacity of the reinforced rock would increase with the lateral stress σ_(2) but decrease as the moisture content increased.An increase in the moisture content would reduce the extent of the influence of the lateral stress on the load bearing capacity of the reinforced rock.In addition,much less AE counts were recorded when the moisture content increased indicating that the crack initiation and propagation in this case was easier due to the reduction of the required external input energy.With increasing moisture content,the failure mode of the specimen gradually changes from sudden and brittle to progressive and ductile.Moreover,the hydration reaction became more significant leading to a complete debonding between the grout and the rock.Consequently,the reinforcement provided by the rock bolt to the rock became negligible.
基金The Key Science Foundation of Liaoning ProvincialCommunications Department (No.0101).
文摘An anchorage reliability analysis approach for simply supported reinforced concrete beams under corrosion attack in the anchorage zone is developed.The first-order second-moment method is employed to analyze the effects of various factors on the anchorage reliability.These factors include both the length and width of cover cracking due to reinforcement corrosion,the cover thickness,the anchorage length,and the stirrup ratio.The results show that the effect of corrosion-induced crack length on the reliability index for anchorage,β0,is negligible when the crack on the concrete surface is just appearing,but with the crack widening,the β0 value is reduced significantly;the considerable changes in β0 result from a variation in cover depth and anchorage length;the effect of changes in the diameter or space of stirrups on the anchorage resistance is very limited,and the variation in β0 is also very low.
文摘The complex tunnelling constructive environment in urban area in similar green field situations is faced through analytical evaluations in order to control the design calculation process and subsequently manage the interventions techniques with the aim of totally reducing the typical settlements trough above the tunnel either during the construction stage or during the serviceability stage. Recently, the author has proposed an operative and mathematical method by an opportune choice of tensioned anchors to control the tunnel lining settlements. In order to completely eliminate the remainder typical soft soil trough which is normal to the line of the tunnel, it is here proposed to use and properly calculate the interventions of stone columns by the SAVE （silent, advanced, vibration-erasing） Compozer method, in combination with the anchorages.
基金supported by the National Natural Science Foundation of China(51734009)National Key Basic Research and Development Program of China(2017YFC0603001).
文摘This paper investigated the stress evolution,displacement field,local deformation and its overall distribution,and failure characteristics of the anchorage structure of surrounding rock with different rockbolt spacing through the model experiments.The influences of the pre-tightening force and spacing of rockbolt on the support strength of the anchorage structure of surrounding rock were analyzed by the simulation using FLAC3D numerical software.The support scheme of the excavated roadway was then designed,and the effectiveness of this support scheme was further verified by the displacement measurement of the roadway.The results showed that the maximum displacement between the roof and floor of the west wing track roadway in Kouzidong coal mine,China is about 42 mm,and the maximum displacement between its both sides is about 72 mm,indicating that the support scheme proposed in this study can ensure the stability and safety of the excavated roadway.
基金supported by the Fundamental Research Funds for the Central Universities(No.YX2010-20)the Open Projects Foundation of Key Laboratory of Soil and Water Conservation & Desertification Combat (Beijing ForestryUniversity), Ministry of Education of P.R. China (No.201002) the National Natural Science Foundation of China (No. 31570708, No.30901162)
文摘It is important to quantify the effect of the root diameter, the embedment length of the root and load speed on the soil-root interface mechanical properties for studying the root anchorage. The soilroot interface mechanical properties can be obtained through the pullout force and root slippage curve(F-S curve). About 120 Pinus tabulaeformis single roots whose diameters ranged from 1 mm to 10 mm divided into 6 groups based on different root embedment length(50 mm, 100 mm and 150 mm) and different load velocity(10 mm·min^(-1), 50 mm·min^(-1), 100 mm·min^(-1) and 300 mm·min^(-1)) were investigated using the pullout method. This study aims to explore the mechanical properties of the soil-root interface in the real conditions using the pullout test method. The results showed two kinds of pullout test failure modes during the experimental process: breakage failure and pullout failure. The results showed that the roots were easier to be broken when the root diameter was smaller or the loading speed was larger. The relationship between the maximum anchorage force and root diameter was linear and the linearly dependent coefficient(R^2) was larger than 0.85. The anchorage force increased with the root embedment length. An increase of 10%^(-1)5% for the maximumanchorage force was found when load speed increased from 10 to 300 mm.min^(-1). The mean peak slippage of the root was from 13.81 to 35.79 mm when the load velocity varied from 10 to 300 mm.min^(-1). The study will be helpful for the design of slopes reinforced by vegetation and in predicting risk of uprooting of trees, and will have practical benefits for understanding the mechanism of landslide.
基金Project(20050532021) supported by the Research Fund for the Doctoral Program of Higher Education
文摘Based on the fact that the shear stress along anchorage segment is neither linearly nor uniformly distributed, the load transfer mechanism of the tension type anchor was studied and the mechanical characteristic of anchorage segment was analyzed. Shear stress?strain relationship of soil surrounding anchorage body was simplified into three-folding-lines model consisting of elastic phase, elasto-plastic phase and residual phase considering its softening characteristic. Meanwhile, shear displacement method that has been extensively used in the analysis of pile foundation was introduced. Based on elasto-plastic theory, the distributions of displacement, shear stress and axial force along the anchorage segment of tension type anchor were obtained, and the formula for calculating the elastic limit load was also developed accordingly. Finally, an example was given to discuss the variation of stress and displacement in the anchorage segment with the loads exerted on the anchor, and a program was worked out to calculate the anchor maximum bearing capacity. The influence of some parameters on the anchor bearing capacity was discussed, and effective anchorage length was obtained simultaneously. The results show that the shear stress first increases and then decreases and finally trends to the residual strength with increase of distance from bottom of the anchorage body, the displacement increases all the time with the increase of distance from bottom of the anchorage body, and the increase of velocity gradually becomes greater.
基金the National Natural Science Foundation of China(Nos.41807265,41972286)the Fundamental Research Funds for the Central Universities,China University of Geosciences(Wuhan)(No.CUGQY1931)。
文摘The stability of the anchorage slope on the Baiyang Yangtze River Highway Bridge in Yichang,China,was investigated under different rainfall conditions using model test,numerical simulation,and factor analysis.The results of the study are as follows:(1)with the increase of rainfall intensity,the change of earth pressure can be divided into three stages.However,when the rainfall intensity was larger than a certain value,the change of earth pressure of cut slope became two stages;with the increase of rainfall intensity,pore water pressure increased with the increase of rainfall time,while at a certain stage after the rainfall,the pore water pressure in the cut slope did not decrease immediately,but increased for a period of time.(2)When the rainfall stopped,the stability coefficient of the anchorage slope continued to decrease,then slowly increased,and finally tended to be gentle.Meanwhile,when the rainstorm reached a certain intensity,the main factor that restricted the rainfall infiltration rate became the geotechnical permeability coefficient of the cut slope,which was no longer the rainfall intensity.(3)Factor analysis shows that the rainfall intensity and rainfall duration were the most important factors for anchorage slope stability,while earth pressure,pore water pressure and slope displacement were much less significant.
基金Project supported by the National Natural Science Foundation of China (No. 10672191)the Specialized Research Fund for the Doctoral Program of Higher Education (No. 20090211110016)the Natural Science Foundation of Gansu Province of China (No. 096RJZA048)
文摘With the help of plant roots, slope vegetation makes the slope soil mass become a composite material of soil and roots, and thus enhances shear strength of the slope soil mass and stability of the slope. However, the related studies at present are still qualitative. In this paper, quantitative analysis of the interaction between roots and soil mass are made. By the analysis of the interaction between herbaceous plant roots including lateral roots of woody plants and rock and soil mass, a mechanical model of the interaction between frictional roots and soil is established, and its correctness is shown. A mechanical model of the interaction between anchorage root, namely, woody plant taproot, and soil is also established. The establishment of the models provides a useful means in quantitative analysis of the interaction between plant roots and soil, and has practical values.
基金Projects(51774196,41472280,51578327)supported by the National Natural Science Foundation of ChinaProject(2016M592221)supported by the China Postdoctoral Science FoundationProject(BJRC20160501)supported by the SDUST Young Teachers Teaching Talent Training Plan,China
文摘Anchoring mechanism and failure characteristics of composite soft rock with weak interface usually exhibit remarkable difference from those in single rock mass.In order to fully understand the reinforcement mechanism of composite soft roof in western mining area of China,a mechanical model of composite soft rock with weak interface and rock bolt which considering the transverse shear sliding between different rock layers was established firstly.The anchoring effect was quantified by a factor defined as anchoring effect coefficient and its evolution equation was further deduced based on the deformation relationship and homogenized distribution assumption of stress acting on composite structure.Meanwhile,the numerical simulation model of composite soft rock with shear joint was prompted by finite element method.Then detailed analysis were carried out for the deformation features,stress distribution and failure behavior of rock mass and rock bolt near the joint under transverse load.The theoretical result indicates that the anchoring effect of rock-bolt through weak joint changes with the working status of rock mass and closely relates with the physical and geometric parameters of rock mass and rock bolt.From the numerical results,the bending deformation of rock bolt accurately characterized by Doseresp model is mainly concentrated between two plastic hinges near the shear joint.The maximum tensile and compression stresses distribute in the plastic hinge.However,the maximum shear stress appears at the positions of joint surface.The failure zones of composite rock are produced firstly at the joint surface due to the reaction of rock bolt.The above results laid a theoretical and computational foundation for further study of anchorage failure in composite soft rock.
基金Projects(51308273,41372307,41272326) supported by the National Natural Science Foundation of ChinaProjects(2010(A)06-b) supported by Science and Technology Fund of Yunan Provincial Communication Department,China
文摘Based on some assumptions, the dynamic analysis model of anchorage system is established. The dynamic governing equation is expressed as finite difference format and programmed by using MATLAB language. Compared with theoretical method, the finite difference method has been verified to be feasible by a case study. It is found that under seismic loading, the dynamic response of anchorage system is synchronously fluctuated with the seismic vibration. The change of displacement amplitude of material points is slight, and comparatively speaking, the displacement amplitude of the outside point is a little larger than that of the inside point, which shows amplification effect of surface. While the axial force amplitude transforms considerably from the inside to the outside. It increases first and reaches the peak value in the intersection between the anchoring section and free section, then decreases slowly in the free section. When considering damping effect of anchorage system, the finite difference method can reflect the time attenuation characteristic better, and the calculating result would be safer and more reasonable than the dynamic steady-state theoretical method. What is more, the finite difference method can be applied to the dynamic response analysis of harmonic and seismic random vibration for all kinds of anchor, and hence has a broad application prospect.
基金supported by the National Natural Science Foundation (Grant No. 51408495)Key R & D projects in Sichuan Province (2020YFG0123)
文摘A tunnel-type anchorage(TTA)is one of the main components in suspension bridges:the bearing mechanism is a key problem.Investigating the deformation characteristics,development law,and failure phenomenon of a TTA under load can provide the theoretical basis for a robust design.Utilizing the TTA of the Jinsha River suspension bridge at Lijiang Shangri-La railway as a prototype,a laboratory model test of the TTA was carried out for three different contact conditions between the anchorage body and the surrounding rock.The stress and deformation distribution law of the anchorage body and its surrounding rock were studied,and the ultimate bearing capacity and failure mode of the TTA were analyzed.The test results show that the compressive stress level is highest at the rear part of the anchorage body.Moving away from the rear portion of the body,the stress decays in a negative exponential function.Based on the load transfer curve,the calculation formula for the shear stress on the contact surface between the anchorage body and the surrounding rock was derived,which shows that the distribution of the shear stress along the axial direction of the anchorage body is not uniform.The distance from the maximum value to the loading surface is approximately 1/3 of the length of the anchorage body,and the stress decreases as the distance from the loading surface increases.Furthermore,the contact condition between the anchorage body and surrounding rock has a great influence on the bearing capacity of the TTA.The increase in the anti-skid tooth ridge and radial anchor bolt can improve the cooperative working capacity of the anchorage body and the surrounding rock,which is approximately 50%higher than that of the flat contact condition.The main function of the anchor bolt is to increase the overall rigidity of the TTA.The contact condition between the anchorage body and the surrounding rock will lead to a change in the failure mode of the TTA.With an increase in the degree of contact,the failure mode will change from shear sliding along the interface to trumpet-shaped inverted cone-shaped failure extending into the surrounding rock.
文摘A growing number of studies have reported that mini-implants do not remain in exactly the same position during treatment, although they remain stable. The aim of this review was to collect data regarding primary displacement immediately straight after loading and secondary displacement over time. A systematic review was performed to investigate primary and secondary displacement. The amount and type of displacement were recorded. A total of 27 studies were included. Sixteen in vitro studies or studies using finite element analysis addressed primary displacement, and nine clinical studies and two animal studies addressed secondary displacement. Significant primary displacement was detected （6.4-24.4 μm） for relevant orthodontic forces （0.5-2.5 N）. The mean secondary displacement ranged from 0 to 2.7 mm for entire mini-implants, The maximum values for each clinical study ranged from 1.0 to 4.1 mm for the head, 1.0 to 1.5 for the body and 1,0 to 1.92 mm for the tail part. The most frequent type of movement was controlled tipping or bodily movement. Primary displacement did not reach a clinically significant level. However, clinicians can expect relevant secondary displacement in the direction of force. Consequently, decentralized insertion within the inter-radicular space, away from force direction, might be favourable. More evidence is needed to provide quantitative recommendations.
文摘The aim of this retrospective study was to quantitatively evaluate the treatment effects of in- trusion of overerupted maxillary molars using miniscrew implant anchorage and to investigate the apical root resorption after molar intrusion. The subjects included 30 patients whose average ages were 35.5±9.0 years. All patients had received intrusion treatments for overerupted maxillary molars with miniscrew anchorage. There were 38 maxillary first molars and 26 maxillary second molars to be in- truded. Two miniscrews were inserted in the buccal and palatal alveolar bone mesial to the overerupted molar. Force of 100-150 g was applied by the elastic chains between screw head and attachment on each side. Lateral cephalograms and panoramic radiographs taken before and after intrusion were used to evaluate dental changes and root resorption of molars. Only 6 of the 128 miniscrews failed. The first and second molars were significantly intruded by averages of 3.4 mm and 3.1 mm respectively （P〈0.001）. The average intrusion time was more than 6 months. The crown of the molars mesially tilted by averages of 3.1 degrees and 3.3 degrees （P〈0.001） for first and second molars. The amounts of root resorption were 0.2-0.4 mm on average. The intrusion treatment of overerupted molars with miniscrew anchorages could be used as an efficient and reliable method to recover lost restoration space for pros- thesis. Radiographically speaking, root resorption of molars was not clinically significant after applica- tion of intrusive forces of 200 to 300 g.
文摘Miniscrews offer a reliable alternative for anchorage during orthodontic treatment,particularly for non-cooperative patients or periodontal patients with alveolar bone loss.The study aims at assessing the correlation of various clinical indicators with the success or failure of miniscrews used for anchorage during orthodontic treatment.Thirty-four consecutive patients with a cumulative total of 82 miniscrews implanted participated in the study.Generalized Estimating Equations were used to assess the correlation of various factors with success rates.The miniscrew was considered the unit of analysis clustered within site and within patient.The overall success rate of miniscrews was 90.2%.For every additional miniscrew used in a patient＇s oral cavity,the success rate was reduced by 67%.Retromandibular triangle and palatal placement and in movable mucosa resulted in lower success rate.The miniscrew length and diameter were found to correlate with success rates.Orthodontic force applied on miniscrews for uprighting purposes showed a lower success rate than that used for retraction.This study revealed that miniscrews present high success rates.The number of miniscrews used per patient,the miniscrew site placement,the soft tissue type of placement,the miniscrew length and diameter as well as the orthodontic force applied on the miniscrew showed significant correlation with success rates.
基金strongly supported by the National Natural Science Foundation of China(Project No.41672320 and 41877280)the National Key R&D Program of China(NO.2018YFC0407002)+3 种基金the Foreign experts Program of Hubei Province(WGZJ2020000011)the Fundamental Research Funds for Central Public Welfare Research Institutes(CKSF 2019180/YT)the Research and Transformation Project of the Changjiang River Scientific Research Institute(CKZS2017007/YT)the Innovation Team Project of the Changjiang River Scientific Research Institute(CKSF2017066/YT)。
文摘The long-term stability of a prestressed anchored slope might be influenced by the durability of the anchorage structure.To understand long-term stability of anchored rock slopes,the research presented herein evaluated the performance evolution of a prestressed anchored bedding slope system in a corrosive environment by model test.The corrosion process in a prestressed anchor bar was monitored in terms of its open-circuit potential(OCP),corrosion current density(CCD),and electrochemical impedance spectroscopy(EIS).The stability of the prestressed anchored slope was evaluated by monitoring changes in anchorage force and displacements.The experimental results show that prestress and oxygen could reduce the corrosion resistance of the anchor bar,and anchor bars in a chloride-rich environment are very susceptible to corrosion.Prestressed tendons in a corrosive environment suffer a loss of anchorage force,the prestress decreases rapidly after locking,and the rate thereof decreases until stabilising;in the later stage,corrosion leads to the reduction of the cross-sectional area of the steel bar which may cause the reduction in anchorage force again.Anchorage force controls the deformation and stability of the anchored slope,the prestress loss caused by later corrosion may lead to an increased rate of displacement and stability degradation of the prestressed anchored rock slope.
