Predicting rock cracking is important for assessing the stability of underground engineering.The effects of the intersecting angle a and the distribution orientation angleβof intersecting fissures on the uniaxial com...Predicting rock cracking is important for assessing the stability of underground engineering.The effects of the intersecting angle a and the distribution orientation angleβof intersecting fissures on the uniaxial compressive strength and the failure characteristics of sandstone containing intersecting fissures are investigated through laboratory experiments and two-dimensional particle flow code(PFC2D).The relationship between the mechanical properties of sandstone and the intersecting angle a and the distribution orientation angleβis analysed.Crack initiation forms and the final failure modes are then categorised and determined via empirical methods.In addition,the cracking processes of intersecting fissures with different a andβvalues are discussed.The results show that variations in the peak stress,peak strain,average modulus,and crack initiation stress of sandstone containing intersecting fissures show a“moth”shape in the space of the a-β-mechanical parameters.Two crack initiation forms are identified:inner tip cracking(usually accompanied by one outer tip cracking)and only outer tips cracking.Two failure modes are observed:(1)the main fracture planes are created at the inner tip and one outer tip,and(2)the main fracture planes are formed at the two outer tips.Two main crack evolution processes of sandstone containing intersecting fissures under uniaxial compression are found.Approaches for quickly determining the crack initiation form and the failure mode are proposed.The combination of the determination equations for the crack initiation form and the failure mode can be used to predict the crack evolution.The approach for determining the crack evolution processes is hence proposed with acceptable precision.展开更多
The paper focuses on the formation of Nanzhangzhuang ground fissure through emphatically analysing factors including the intersection fault dislocation,the deep ground-water over-exploitation together with the landfor...The paper focuses on the formation of Nanzhangzhuang ground fissure through emphatically analysing factors including the intersection fault dislocation,the deep ground-water over-exploitation together with the landform and lithology features.Features of the ground fissure are explained in detail after describing the geological setting in the study area.The paper also provides dynamic mode of the ground fissure formation via force analysis of the soil body unit at ground fissures.Conclusions can be drawn that the stress state of soil bodies changed with the activities of two intersection faults,namely Hengshui fault and Hubei fault.In addition,the stress fields control the development of ground fissure.The deep groundwater in Hengshui area dropped considerably in recent years,to be precise,the water elevation of deep groundwater dropped from -26 m to -94 m by 2010 at the centre of groundwater funnel.The over-exploitation of deep groundwater in Hengshui area enlarged the ground fissures.The data concerning shallow borehole show that the vertical lithology mainly consists of silt,silty clay and silty sandy soil,which all belong to the middle-compressed soil.The lateral extension of the soil bodies occur with pumping and tectonic creep,and the clay layers on both sides of the cracks can stay upright.Thus the ground fissure came visible.展开更多
基金supported by the National Key R&D Program of China(Grant No.2018YFC1504802)the National Natural Science Foundation of China(Grant No.52074042)the Basic Research and Frontier Exploration Project of Chongqing,China in 2018(Grant No.cstc2018jcyj AX0453)。
文摘Predicting rock cracking is important for assessing the stability of underground engineering.The effects of the intersecting angle a and the distribution orientation angleβof intersecting fissures on the uniaxial compressive strength and the failure characteristics of sandstone containing intersecting fissures are investigated through laboratory experiments and two-dimensional particle flow code(PFC2D).The relationship between the mechanical properties of sandstone and the intersecting angle a and the distribution orientation angleβis analysed.Crack initiation forms and the final failure modes are then categorised and determined via empirical methods.In addition,the cracking processes of intersecting fissures with different a andβvalues are discussed.The results show that variations in the peak stress,peak strain,average modulus,and crack initiation stress of sandstone containing intersecting fissures show a“moth”shape in the space of the a-β-mechanical parameters.Two crack initiation forms are identified:inner tip cracking(usually accompanied by one outer tip cracking)and only outer tips cracking.Two failure modes are observed:(1)the main fracture planes are created at the inner tip and one outer tip,and(2)the main fracture planes are formed at the two outer tips.Two main crack evolution processes of sandstone containing intersecting fissures under uniaxial compression are found.Approaches for quickly determining the crack initiation form and the failure mode are proposed.The combination of the determination equations for the crack initiation form and the failure mode can be used to predict the crack evolution.The approach for determining the crack evolution processes is hence proposed with acceptable precision.
基金Hebei Province Natural Science Foundation of China(D2017403020)the Joint foundation of Key Laboratory of Institute of Hydrogeology and Environmental Geology,Chinese Academy of Geological Sciences(KF201602)
文摘The paper focuses on the formation of Nanzhangzhuang ground fissure through emphatically analysing factors including the intersection fault dislocation,the deep ground-water over-exploitation together with the landform and lithology features.Features of the ground fissure are explained in detail after describing the geological setting in the study area.The paper also provides dynamic mode of the ground fissure formation via force analysis of the soil body unit at ground fissures.Conclusions can be drawn that the stress state of soil bodies changed with the activities of two intersection faults,namely Hengshui fault and Hubei fault.In addition,the stress fields control the development of ground fissure.The deep groundwater in Hengshui area dropped considerably in recent years,to be precise,the water elevation of deep groundwater dropped from -26 m to -94 m by 2010 at the centre of groundwater funnel.The over-exploitation of deep groundwater in Hengshui area enlarged the ground fissures.The data concerning shallow borehole show that the vertical lithology mainly consists of silt,silty clay and silty sandy soil,which all belong to the middle-compressed soil.The lateral extension of the soil bodies occur with pumping and tectonic creep,and the clay layers on both sides of the cracks can stay upright.Thus the ground fissure came visible.
