Rock slope instability is a prevalent geological hazard that imposes significant adverse impacts on engineering activities.Although existing studies have focused on homogeneous rock slopes,the theoretical models for q...Rock slope instability is a prevalent geological hazard that imposes significant adverse impacts on engineering activities.Although existing studies have focused on homogeneous rock slopes,the theoretical models for quantifying the stability of softhard interbedded anti-inclined slopes remain underdeveloped,primarily due to the complex force transfer mechanisms involved.This study proposed a novel theoretical model for the stability analysis of soft-hard interbedded anti-inclined slopes under rainfall conditions.The framework models stratified rock layers as layered cantilever beams with material heterogeneity.Based on the principle of deformation compatibility,it comprehensively accounted for interlayer force transfer and strength degradation resulting from differential deformations among rock layers.Furthermore,it integrated the critical instability length induced by the self-weight of rock layers to determine the fracture depth.The proposed method was validated against engineering case studies and physical model tests,with error falling within an acceptable range.Compared to existing theoretical methods,the proposed method provided a more realistic representation of the slope's stress field.The analysis results demonstrate that rainfall not only reduces the inclination angle of the failure surface but also leads to an approximate 30%decrease in the safety factor.The proposed theoretical model is particularly useful for quickly calculating the stability of soft-hard interbedded anti-inclined rock slope under rainfall conditions,compared to complex and time-consuming numerical simulation calculations.展开更多
To investigate the long-term stability of soft-hard interbedded rock masses with initial damage induced by earthquakes and periodic drying and wetting,this study prepared samples with different initial damage through ...To investigate the long-term stability of soft-hard interbedded rock masses with initial damage induced by earthquakes and periodic drying and wetting,this study prepared samples with different initial damage through cyclic loading and unloading(CLU)experiments followed by cyclic drying and wetting(CDW)experiments,and finally conducted creep experiments.The study analyzed the effects of initial damage on creep mechanical behavior,crack evolution,and explored failure precursor information,revealing the damage failure mechanisms.The results show that the structural characteristics of the rock mass control its macroscopic failure mode.Initial damage promotes microcrack development,influences the fracture mode,and increases the proportion of high-frequency(200−280 kHz)acoustic emission events during creep.Meanwhile,initial damage exacerbates creep characteristics,increasing the creep rate,shortening total creep failure time,and reducing long-term strength.The damage failure is attributed to:the generation of internal cracks and pores in the rock caused by CLU;mineral hydrolysis and expansion-contraction due to CDW,resulting in weakened intergranular cementation;and full development of cracks and pores under creep stress.Additionally,the deformation difference coefficient and the coefficient of variation of RA/AF values can serve as precursor indicators for creep failure.展开更多
Due to the effects of seismic wave field interference, the reflection events generated from interbedded and superposed sand and shale strata no longer have an explicit corresponding relationship with the geological in...Due to the effects of seismic wave field interference, the reflection events generated from interbedded and superposed sand and shale strata no longer have an explicit corresponding relationship with the geological interface. The absorption of the near-surface layer decreases the resolution of the seismic wavelet, intensifies the interference of seismic reflections from different sand bodies, and makes seismic data interpretation of thin interbedded strata more complex and difficult. In order to concretely investigate and analyze the effects of the near-surface absorption on seismic reflection characteristics of interbedded strata, and to make clear the ability of current technologies to compensate the near-surface absorption, a geological model of continental interbedded strata with near-surface absorption was designed, and the prestack seismic wave field was numerically simulated with wave equations. Then, the simulated wave field was processed by the prestack time migration, the effects of near-surface absorption on prestack and poststack reflection characteristics were analyzed, and the near-surface absorption was compensated for by inverse Q-filtering. The model test shows that: (1) the reliability of prediction and delineation of a continental reservoir with AVO inversion is degraded due to the lateral variation of the near-surface structure; (2) the corresponding relationships between seismic reflection events and geological interfaces are further weakened as a result of near-surface absorption; and (3) the current technology of absorption compensation probably results in false geological structure and anomaly. Based on the model experiment, the real seismic data of the Dagang Oil Field were analyzed and processed. The seismic reflection characteristics of continental interbedded strata were improved, and the reliability of geological interpretation from seismic data was enhanced.展开更多
Three-dimensional(3D)printing technology is increasingly used in experimental research of geotechnical engineering.Compared to other materials,3D layer-by-layer printing specimens are extremely similar to the inherent...Three-dimensional(3D)printing technology is increasingly used in experimental research of geotechnical engineering.Compared to other materials,3D layer-by-layer printing specimens are extremely similar to the inherent properties of natural layered rock masses.In this paper,soft-hard interbedded rock masses with different dip angles were prepared based on 3D printing(3DP)sand core technology.Uniaxial compression creep tests were conducted to investigate its anisotropic creep behavior based on digital imaging correlation(DIC)technology.The results show that the anisotropic creep behavior of the 3DP soft-hard interbedded rock mass is mainly affected by the dip angles of the weak interlayer when the stress is at low levels.As the stress level increases,the effect of creep stress on its creep anisotropy increases significantly,and the dip angle is no longer the main factor.The minimum value of the long-term strength and creep failure strength always appears in the weak interlayer within 30°–60°,which explains why the failure of the layered rock mass is controlled by the weak interlayer and generally emerges at 45°.The tests results are verified by comparing with theoretical and other published studies.The feasibility of the 3DP soft-hard interbedded rock mass provides broad prospects and application values for 3DP technology in future experimental research.展开更多
Water-and-mud inrush disasters have become a major challenge in underground engineering for the construction of tunnels in sandstone and slate interbedded Presinian strata.Disaster prediction and prevention rely in pa...Water-and-mud inrush disasters have become a major challenge in underground engineering for the construction of tunnels in sandstone and slate interbedded Presinian strata.Disaster prediction and prevention rely in part on realistic modeling and observation of the disaster process,as well as the identification and examination of the underlying mechanisms.Based on the geological conditions and the historical records of the Xinping Tunnel on the China–Laos Railway,an engineering geological model of the water-and-mud inrush was established.A physical model test that accurately reproduced water-and-mud inrush during tunnel excavation in sandstone and slate interbedded strata was also carried out.Then,testing was conducted that examined the stress and strain,seepage pressure,and high-leakage flow of the surrounding rock.The results indicated that the water-and-mud inrush proceeded through three stages:seepage stage,high-leakage flow stage,and attenuation stage.In essence,the disaster was a catastrophic process,during which the water-resistant stratum was reduced to a critical safety thickness,a water-inrush channel formed,and the water-resistant stratum gradually failed under the influence of excavation unloading and in situ stress–seepage coupling.Parameters such as the stress and strain,seepage pressure,and flow of the surrounding rock had evident stage-related features during water-and-mud inrush,and their variation indicated the formation,development,and evolution of the disaster.As the tunnel face advanced,the trend of the stress–strain curve of the surrounding rock shifted from sluggish to rapid in its speed of increase.The characteristics of strain energy density revealed the erosion and weakening effect of groundwater on the surrounding rock.The seepage pressure and the thickness of the water-resistant stratum had a positive linear relationship,and the flow and thickness a negative linear relationship.There was a pivotal point at which the seepage pressure changed from high to low and the flow shifted from low to high.The thickness of the water-resistant stratum corresponding to the pivotal point was deemed the critical safety thickness.展开更多
Slopes consisting of interbedded strata of soft and hard rock mass, such as purplish red mudstone and grey brown arkosic sandstone of Jurassic age, are very common in Sichuan basin of China. The mudstone is soft whil...Slopes consisting of interbedded strata of soft and hard rock mass, such as purplish red mudstone and grey brown arkosic sandstone of Jurassic age, are very common in Sichuan basin of China. The mudstone is soft while the sandstone is hard and contains many opening or closing joints with a high dip angle. Some are nearly parallel and the others are nearly decussated with the trend of the slopes. Many natural slopes are in deformation or sliding because of those reasons. The stability of cutting slopes and supporting method to be taken for their stability in civil engineering are important. In this paper, the stability and deformation of the slopes are studied. The methods of analysis and support design principle are analyzed also. Finally, the method put forward is applied to study Fengdian high cutting slope in Sichuan section of the express way from Chengdu to Shanghai. The results indicate that the method is effective.展开更多
三峡库区秭归盆地广泛分布以软硬相间地层为主的易滑地层,在长期的库水浸泡冲刷、降雨等作用下,地层岩土体发生劣化损伤,成为降低滑坡稳定和影响工程安全的重要内因。以软硬相间地层岩土体为研究对象,采用有限-离散元法(finite discrete...三峡库区秭归盆地广泛分布以软硬相间地层为主的易滑地层,在长期的库水浸泡冲刷、降雨等作用下,地层岩土体发生劣化损伤,成为降低滑坡稳定和影响工程安全的重要内因。以软硬相间地层岩土体为研究对象,采用有限-离散元法(finite discrete element method,简称FDEM)对不同干湿循环作用下软硬相间地层中硬岩和软岩的力学参数进行了标定,然后通过改进的泰森多边形程序进行了网格重划分,实现了零厚度黏聚力单元的嵌入功能,提出并建立了软硬相间地层滑坡-抗滑桩体系FDE.M数值计算模型,最后对不同干湿循环作用下滑坡裂纹的形成过程和抗滑桩的嵌固机理进行了研究。研究结果表明:(1)滑坡模拟裂纹数量随着干湿循环次数的增加而增多,裂纹宽度也逐渐增大,并与马家沟滑坡现场裂缝进行了对比,模拟结果与现场基本一致;(2)滑坡-抗滑桩体系的模拟裂纹呈现2种演化模式,一是裂纹从桩顶侧岩土体沿着桩身向下扩展,二是裂纹从抗滑桩周围逐渐向滑体内部延伸,与横向裂纹和竖向裂纹连通,最终形成大型的贯通裂纹;(3)当干湿循环次数增加时,抗滑桩桩身水平位移、弯矩和剪力也随之增加;(4)抗滑桩嵌固段的软硬相间地层基岩内的裂纹具有局部化发育特征,而且随干湿循环次数的增加,区域内的应力逐渐减小,位移和应变则逐渐增大,相应的裂纹也愈发密集。研究成果可为不同干湿循环作用下软硬相间地层滑坡防治提供技术支撑。展开更多
基金supported by the Chongqing Water Conservancy Science and Technology Project(grant number:CQSLK-202329)the Natural Science Foundation of Chongqing,China(grant number:CSTB2022NSCQ-MSX0991)+1 种基金the National Natural Science Foundation of China(grant number:52378327)the Chongqing Natural Science Foundation Innovation Development Joint Fund(grant number:CSTB2022NSCQ-LZX0049)。
文摘Rock slope instability is a prevalent geological hazard that imposes significant adverse impacts on engineering activities.Although existing studies have focused on homogeneous rock slopes,the theoretical models for quantifying the stability of softhard interbedded anti-inclined slopes remain underdeveloped,primarily due to the complex force transfer mechanisms involved.This study proposed a novel theoretical model for the stability analysis of soft-hard interbedded anti-inclined slopes under rainfall conditions.The framework models stratified rock layers as layered cantilever beams with material heterogeneity.Based on the principle of deformation compatibility,it comprehensively accounted for interlayer force transfer and strength degradation resulting from differential deformations among rock layers.Furthermore,it integrated the critical instability length induced by the self-weight of rock layers to determine the fracture depth.The proposed method was validated against engineering case studies and physical model tests,with error falling within an acceptable range.Compared to existing theoretical methods,the proposed method provided a more realistic representation of the slope's stress field.The analysis results demonstrate that rainfall not only reduces the inclination angle of the failure surface but also leads to an approximate 30%decrease in the safety factor.The proposed theoretical model is particularly useful for quickly calculating the stability of soft-hard interbedded anti-inclined rock slope under rainfall conditions,compared to complex and time-consuming numerical simulation calculations.
基金Project(U22A20603)supported by the National Natural Science Foundation of ChinaProject(2023YFC3008300)supported by the National Key Research and Development Program of China。
文摘To investigate the long-term stability of soft-hard interbedded rock masses with initial damage induced by earthquakes and periodic drying and wetting,this study prepared samples with different initial damage through cyclic loading and unloading(CLU)experiments followed by cyclic drying and wetting(CDW)experiments,and finally conducted creep experiments.The study analyzed the effects of initial damage on creep mechanical behavior,crack evolution,and explored failure precursor information,revealing the damage failure mechanisms.The results show that the structural characteristics of the rock mass control its macroscopic failure mode.Initial damage promotes microcrack development,influences the fracture mode,and increases the proportion of high-frequency(200−280 kHz)acoustic emission events during creep.Meanwhile,initial damage exacerbates creep characteristics,increasing the creep rate,shortening total creep failure time,and reducing long-term strength.The damage failure is attributed to:the generation of internal cracks and pores in the rock caused by CLU;mineral hydrolysis and expansion-contraction due to CDW,resulting in weakened intergranular cementation;and full development of cracks and pores under creep stress.Additionally,the deformation difference coefficient and the coefficient of variation of RA/AF values can serve as precursor indicators for creep failure.
基金supported by the National 973 Key Basic Research Development Program(No. 2007CB209608)National 863 High Technology Research Development Program(No.2007AA06Z218)
文摘Due to the effects of seismic wave field interference, the reflection events generated from interbedded and superposed sand and shale strata no longer have an explicit corresponding relationship with the geological interface. The absorption of the near-surface layer decreases the resolution of the seismic wavelet, intensifies the interference of seismic reflections from different sand bodies, and makes seismic data interpretation of thin interbedded strata more complex and difficult. In order to concretely investigate and analyze the effects of the near-surface absorption on seismic reflection characteristics of interbedded strata, and to make clear the ability of current technologies to compensate the near-surface absorption, a geological model of continental interbedded strata with near-surface absorption was designed, and the prestack seismic wave field was numerically simulated with wave equations. Then, the simulated wave field was processed by the prestack time migration, the effects of near-surface absorption on prestack and poststack reflection characteristics were analyzed, and the near-surface absorption was compensated for by inverse Q-filtering. The model test shows that: (1) the reliability of prediction and delineation of a continental reservoir with AVO inversion is degraded due to the lateral variation of the near-surface structure; (2) the corresponding relationships between seismic reflection events and geological interfaces are further weakened as a result of near-surface absorption; and (3) the current technology of absorption compensation probably results in false geological structure and anomaly. Based on the model experiment, the real seismic data of the Dagang Oil Field were analyzed and processed. The seismic reflection characteristics of continental interbedded strata were improved, and the reliability of geological interpretation from seismic data was enhanced.
基金the support of the National Natural Science Foundation of China(Grant Nos.42207199,52179113,42272333)Zhejiang Postdoctoral Scientific Research Project(Grant Nos.ZJ2022155,ZJ2022156)。
文摘Three-dimensional(3D)printing technology is increasingly used in experimental research of geotechnical engineering.Compared to other materials,3D layer-by-layer printing specimens are extremely similar to the inherent properties of natural layered rock masses.In this paper,soft-hard interbedded rock masses with different dip angles were prepared based on 3D printing(3DP)sand core technology.Uniaxial compression creep tests were conducted to investigate its anisotropic creep behavior based on digital imaging correlation(DIC)technology.The results show that the anisotropic creep behavior of the 3DP soft-hard interbedded rock mass is mainly affected by the dip angles of the weak interlayer when the stress is at low levels.As the stress level increases,the effect of creep stress on its creep anisotropy increases significantly,and the dip angle is no longer the main factor.The minimum value of the long-term strength and creep failure strength always appears in the weak interlayer within 30°–60°,which explains why the failure of the layered rock mass is controlled by the weak interlayer and generally emerges at 45°.The tests results are verified by comparing with theoretical and other published studies.The feasibility of the 3DP soft-hard interbedded rock mass provides broad prospects and application values for 3DP technology in future experimental research.
基金the National High-Speed Rail United Foundation of China(No.U1934213)。
文摘Water-and-mud inrush disasters have become a major challenge in underground engineering for the construction of tunnels in sandstone and slate interbedded Presinian strata.Disaster prediction and prevention rely in part on realistic modeling and observation of the disaster process,as well as the identification and examination of the underlying mechanisms.Based on the geological conditions and the historical records of the Xinping Tunnel on the China–Laos Railway,an engineering geological model of the water-and-mud inrush was established.A physical model test that accurately reproduced water-and-mud inrush during tunnel excavation in sandstone and slate interbedded strata was also carried out.Then,testing was conducted that examined the stress and strain,seepage pressure,and high-leakage flow of the surrounding rock.The results indicated that the water-and-mud inrush proceeded through three stages:seepage stage,high-leakage flow stage,and attenuation stage.In essence,the disaster was a catastrophic process,during which the water-resistant stratum was reduced to a critical safety thickness,a water-inrush channel formed,and the water-resistant stratum gradually failed under the influence of excavation unloading and in situ stress–seepage coupling.Parameters such as the stress and strain,seepage pressure,and flow of the surrounding rock had evident stage-related features during water-and-mud inrush,and their variation indicated the formation,development,and evolution of the disaster.As the tunnel face advanced,the trend of the stress–strain curve of the surrounding rock shifted from sluggish to rapid in its speed of increase.The characteristics of strain energy density revealed the erosion and weakening effect of groundwater on the surrounding rock.The seepage pressure and the thickness of the water-resistant stratum had a positive linear relationship,and the flow and thickness a negative linear relationship.There was a pivotal point at which the seepage pressure changed from high to low and the flow shifted from low to high.The thickness of the water-resistant stratum corresponding to the pivotal point was deemed the critical safety thickness.
文摘Slopes consisting of interbedded strata of soft and hard rock mass, such as purplish red mudstone and grey brown arkosic sandstone of Jurassic age, are very common in Sichuan basin of China. The mudstone is soft while the sandstone is hard and contains many opening or closing joints with a high dip angle. Some are nearly parallel and the others are nearly decussated with the trend of the slopes. Many natural slopes are in deformation or sliding because of those reasons. The stability of cutting slopes and supporting method to be taken for their stability in civil engineering are important. In this paper, the stability and deformation of the slopes are studied. The methods of analysis and support design principle are analyzed also. Finally, the method put forward is applied to study Fengdian high cutting slope in Sichuan section of the express way from Chengdu to Shanghai. The results indicate that the method is effective.
文摘三峡库区秭归盆地广泛分布以软硬相间地层为主的易滑地层,在长期的库水浸泡冲刷、降雨等作用下,地层岩土体发生劣化损伤,成为降低滑坡稳定和影响工程安全的重要内因。以软硬相间地层岩土体为研究对象,采用有限-离散元法(finite discrete element method,简称FDEM)对不同干湿循环作用下软硬相间地层中硬岩和软岩的力学参数进行了标定,然后通过改进的泰森多边形程序进行了网格重划分,实现了零厚度黏聚力单元的嵌入功能,提出并建立了软硬相间地层滑坡-抗滑桩体系FDE.M数值计算模型,最后对不同干湿循环作用下滑坡裂纹的形成过程和抗滑桩的嵌固机理进行了研究。研究结果表明:(1)滑坡模拟裂纹数量随着干湿循环次数的增加而增多,裂纹宽度也逐渐增大,并与马家沟滑坡现场裂缝进行了对比,模拟结果与现场基本一致;(2)滑坡-抗滑桩体系的模拟裂纹呈现2种演化模式,一是裂纹从桩顶侧岩土体沿着桩身向下扩展,二是裂纹从抗滑桩周围逐渐向滑体内部延伸,与横向裂纹和竖向裂纹连通,最终形成大型的贯通裂纹;(3)当干湿循环次数增加时,抗滑桩桩身水平位移、弯矩和剪力也随之增加;(4)抗滑桩嵌固段的软硬相间地层基岩内的裂纹具有局部化发育特征,而且随干湿循环次数的增加,区域内的应力逐渐减小,位移和应变则逐渐增大,相应的裂纹也愈发密集。研究成果可为不同干湿循环作用下软硬相间地层滑坡防治提供技术支撑。
