The squeezing scenario in deep weak rock tunnels can hinder underground construction.However,due to the limitations of test technologies at hand,the real excavation stress path cannot be mimicked in the laboratory.Thu...The squeezing scenario in deep weak rock tunnels can hinder underground construction.However,due to the limitations of test technologies at hand,the real excavation stress path cannot be mimicked in the laboratory.Thus,the large deformation mechanism of deep weak rocks still remains unclear.For this,a true triaxial apparatus(TTA)to investigate the mechanical responses of deep weak rock under excavation stress paths in field and reveal the squeezing mechanism of deep tunnels is assembled and developed at Northeastern University,China.The apparatus can perform instantaneous unloading in s3 direction based on electromagnetism technology.In addition,uniform loading and deformation measurements can be carried out based on the proposed linked interlocking clamp and antifriction device,even if the sample has a strong dilatation deformation performance.Next,a bore trepanning is designed to capture noiseless acoustic emission(AE)signals for deep weak rock at a low threshold.Finally,two tests were are conducted using this instrument to preliminarily understand the failure and deformation features of deep weak rock based on fractured marble.The results show that the complete stressestrain curves of fractured marble have the characteristics of low strengths and large deformations,and the larger deformation and the more serious failure occur when the fractured marble enters the post-peak state after excavation.The results show that the developed apparatus is likely to be applicable for deep weak rock engineering.展开更多
Rockfill material is widely used for construction of high rockfill dam due to its facility,economical cost,high strength and effective aseismatic property.It is provoked profoundly to propose a suitable constitutive m...Rockfill material is widely used for construction of high rockfill dam due to its facility,economical cost,high strength and effective aseismatic property.It is provoked profoundly to propose a suitable constitutive model for a better application of this material.The dilatancy equation of rockfill material plays a significant role in the constitutive model.For the sake of simplicity,a dilatancy equation is established by the linear least square method on the basis of the rearranged data of rockfill material in the true triaxial tests.Based on the fact that the rearranged data at different initial confining pressures are aligned in a narrow band,the dilatancy behavior of rockfill material is independent of the initial confining pressure.However,different from the initial confining pressure,both the intermediate principal stress ratio and the specimen density exhibit a remarkable influence on the dilatancy behaviors of rockfill material.Furthermore,the predictions of the proposed dilatancy equation are in a good agreement with the rearranged test data of rockfill material at different specimen densities and stress paths.展开更多
基金the financial support from the 111 Project(Grant No.B17009)the Liao Ning Revitalization Talents Program(Grant No.XLYCYSZX1902).
文摘The squeezing scenario in deep weak rock tunnels can hinder underground construction.However,due to the limitations of test technologies at hand,the real excavation stress path cannot be mimicked in the laboratory.Thus,the large deformation mechanism of deep weak rocks still remains unclear.For this,a true triaxial apparatus(TTA)to investigate the mechanical responses of deep weak rock under excavation stress paths in field and reveal the squeezing mechanism of deep tunnels is assembled and developed at Northeastern University,China.The apparatus can perform instantaneous unloading in s3 direction based on electromagnetism technology.In addition,uniform loading and deformation measurements can be carried out based on the proposed linked interlocking clamp and antifriction device,even if the sample has a strong dilatation deformation performance.Next,a bore trepanning is designed to capture noiseless acoustic emission(AE)signals for deep weak rock at a low threshold.Finally,two tests were are conducted using this instrument to preliminarily understand the failure and deformation features of deep weak rock based on fractured marble.The results show that the complete stressestrain curves of fractured marble have the characteristics of low strengths and large deformations,and the larger deformation and the more serious failure occur when the fractured marble enters the post-peak state after excavation.The results show that the developed apparatus is likely to be applicable for deep weak rock engineering.
基金supported by the Key Project of National Natural Science Foundation of China and Yalongjiang Hydroelectric Development Joint Research Fund(Grant No.50639050)the National Natural Science Foundation for Distinguished Young Scholar(Grant No.50825901)+1 种基金the Public Service Sector R&D Project of Ministry of Water Resource of China (Grant No.200801014)China Scholarship Fund(Grant No.2010671026)
文摘Rockfill material is widely used for construction of high rockfill dam due to its facility,economical cost,high strength and effective aseismatic property.It is provoked profoundly to propose a suitable constitutive model for a better application of this material.The dilatancy equation of rockfill material plays a significant role in the constitutive model.For the sake of simplicity,a dilatancy equation is established by the linear least square method on the basis of the rearranged data of rockfill material in the true triaxial tests.Based on the fact that the rearranged data at different initial confining pressures are aligned in a narrow band,the dilatancy behavior of rockfill material is independent of the initial confining pressure.However,different from the initial confining pressure,both the intermediate principal stress ratio and the specimen density exhibit a remarkable influence on the dilatancy behaviors of rockfill material.Furthermore,the predictions of the proposed dilatancy equation are in a good agreement with the rearranged test data of rockfill material at different specimen densities and stress paths.
