Based on the similarity theory,a tunnel excavation simulation testing system under typical unsymmetrical loading conditions was established.Using this system,the failure mechanism of surrounding rock of shallow-bias t...Based on the similarity theory,a tunnel excavation simulation testing system under typical unsymmetrical loading conditions was established.Using this system,the failure mechanism of surrounding rock of shallow-bias tunnels with small clear distance was analyzed along with the load characteristics.The results show that:1) The failure process of surrounding rock of shallow-bias tunnels with small clear distance consists of structural and stratum deformation induced by tunnel excavation; Microfracture surfaces are formed in the tunnel surrounding rock and extend deep into the rock mass in a larger density; Tensile cracking occurs in shallow position on the deep-buried side,with shear slip in deep rock mass.In the meantime,rapid deformation and slip take place on the shallow-buried side until the surrounding rocks totally collapse.The production and development of micro-fracture surfaces in the tunnel surrounding rock and tensile cracking in the shallow position on the deep-buried side represent the key stages of failure.2) The final failure mode is featured by an inverted conical fracture with tunnel arch as its top and the slope at tunnel entrance slope as its bottom.The range of failure on the deep-buried side is significantly larger than that on the shallow-buried side.Such difference becomes more prominent with the increasing bias angle.What distinguishes it from the "linear fracture surface" model is that the model proposed has a larger fracture angle on the two sides.Moreover,the bottom of the fracture is located at the springing line of tunnel arch.3) The total vertical load increases with bias angle.Compared with the existing methods,the unsymmetrical loading effect in measurement is more prominent.At last,countermeasures are proposed according to the analysis results: during engineering process,1) The surrounding rock mass on the deep-buried side should be reinforced apart from the tunnel surrounding rock for shallow-buried tunnels with small clear distance; moreover,the scope of consolidation should go beyond the midline of tunnel(along the direction of the top of slope) by 4 excavation spans of single tunnel.2) It is necessary to modify the load value of shallow-bias tunnels with small clear distance.展开更多
Reinforced concrete(RC) columns are widely used as supporting structures for high-piled wharfs.The study of damage model of a RC column due to underwater explosion is a critical issue to assess the wharfs antiknock se...Reinforced concrete(RC) columns are widely used as supporting structures for high-piled wharfs.The study of damage model of a RC column due to underwater explosion is a critical issue to assess the wharfs antiknock security.In this study,the dynamic response and damage model of circular RC columns subjected to underwater explosions were investigated by means of scaled-down experiment models.Experiments were carried out in a 10.0 m diameter tank with the water depth of 2.25 m,under different explosive quantities(0.025 kg-1.6 kg),stand-off distances(0.0 m-7.0 m),and detonation depths(0.25 m-2.0 m).The shock wave load and dynamic response of experiment models were measured by configuring sensors of pressure,acceleration,strain,and displacement.Then,the load distribution characteristics,time history of test data,and damage models related to present conditions were obtained and discussed.Three damage models,including bending failure,bending-shear failure and punching failure,were identified.In addition,the experie nce model of shock wave loads on the surface of a RC column was proposed for engineering application.展开更多
基金Project(51508575)supported by the National Natural Science Foundation of ChinaProject(2011CB013802)supported by the National Basic Research Program of China+1 种基金Projects(2014M560652,2016T90764)supported by the China Postdoctoral Science FoundationProject(2015RS4006)supported by the Innovative Talents of Science and Technology Plan of Hunan Province,China
文摘Based on the similarity theory,a tunnel excavation simulation testing system under typical unsymmetrical loading conditions was established.Using this system,the failure mechanism of surrounding rock of shallow-bias tunnels with small clear distance was analyzed along with the load characteristics.The results show that:1) The failure process of surrounding rock of shallow-bias tunnels with small clear distance consists of structural and stratum deformation induced by tunnel excavation; Microfracture surfaces are formed in the tunnel surrounding rock and extend deep into the rock mass in a larger density; Tensile cracking occurs in shallow position on the deep-buried side,with shear slip in deep rock mass.In the meantime,rapid deformation and slip take place on the shallow-buried side until the surrounding rocks totally collapse.The production and development of micro-fracture surfaces in the tunnel surrounding rock and tensile cracking in the shallow position on the deep-buried side represent the key stages of failure.2) The final failure mode is featured by an inverted conical fracture with tunnel arch as its top and the slope at tunnel entrance slope as its bottom.The range of failure on the deep-buried side is significantly larger than that on the shallow-buried side.Such difference becomes more prominent with the increasing bias angle.What distinguishes it from the "linear fracture surface" model is that the model proposed has a larger fracture angle on the two sides.Moreover,the bottom of the fracture is located at the springing line of tunnel arch.3) The total vertical load increases with bias angle.Compared with the existing methods,the unsymmetrical loading effect in measurement is more prominent.At last,countermeasures are proposed according to the analysis results: during engineering process,1) The surrounding rock mass on the deep-buried side should be reinforced apart from the tunnel surrounding rock for shallow-buried tunnels with small clear distance; moreover,the scope of consolidation should go beyond the midline of tunnel(along the direction of the top of slope) by 4 excavation spans of single tunnel.2) It is necessary to modify the load value of shallow-bias tunnels with small clear distance.
基金funded by the National Natural Science Foundation of China(Grant Nos.51578543)。
文摘Reinforced concrete(RC) columns are widely used as supporting structures for high-piled wharfs.The study of damage model of a RC column due to underwater explosion is a critical issue to assess the wharfs antiknock security.In this study,the dynamic response and damage model of circular RC columns subjected to underwater explosions were investigated by means of scaled-down experiment models.Experiments were carried out in a 10.0 m diameter tank with the water depth of 2.25 m,under different explosive quantities(0.025 kg-1.6 kg),stand-off distances(0.0 m-7.0 m),and detonation depths(0.25 m-2.0 m).The shock wave load and dynamic response of experiment models were measured by configuring sensors of pressure,acceleration,strain,and displacement.Then,the load distribution characteristics,time history of test data,and damage models related to present conditions were obtained and discussed.Three damage models,including bending failure,bending-shear failure and punching failure,were identified.In addition,the experie nce model of shock wave loads on the surface of a RC column was proposed for engineering application.
