Experiment And Numerical Simulation Of Surface Rupture Deformation Under Strong Earthquake

The surface rupture of strong earthquake often causes great damage to buildings.A series of research work around the fracture mechanism and avoidance of overburden soil on active faults is a hot issue in engineering and academic circles.In this paper,the multi-mode data of "strong earthquake ground fracture zone foundation" and "strong earthquake ground fracture zone foundation superstructure" are analyzed and analyzed by combining large-scale surface fracture model test with numerical simulation of large deformation of surface fracture,The failure mechanism on the fracture zone is revealed and the concept of fracture resistance is deepened.The main contents are as follows:1.Large scale model box test analysis of cohesive soil under different fault types(positive and negative)(1)The main fracture forms and fracture forms of the positive and reverse fault soil layers,the uneven settlement range of the surface and the slope of different positions are obtained.(2)The dislocation of bedrock is much smaller than that of the reverse fault.(3)No matter the surface fracture zone of the positive and reverse fault tests are distributed in the upper soil layer,there is no obvious crack in the lower soil layer,and the change value of soil pressure near the upper plate and the main fracture is also greater than that of the lower plate.(4)From the influence range of fault avoidance,the deformation range of the main fault zone on the surface of the reverse fault is larger than that of the normal fault;The comprehensive analysis shows that the range of the deviation width of the positive and reverse faults is about 3:1.2.The test analysis of large-scale model box of different soil types(clay and sand)under normal fault(1)The shear fracture zone of sand is much smaller than that of clay;When the fracture is complete,the main fracture zone of the clay surface bulges and bulges,while the main fracture zone of sand land collapses and depressions.(2)Based on the analysis of the test phenomenon,the displacement of the surface and the internal pressure of the soil,the fault influence range under the clay condition is larger than that of the sand.(3)Under normal fault test,the comparison of acceleration records shows that:(I)the peak acceleration of the upper surface soil layer is about 1.4-2.8 times of that of the lower plate under the condition of cohesive soil;However,the effect of the upper plate is not obvious,but after the complete fracture,the peak acceleration of the bottom plate of the sand is greater than that of the upper plate(II)the acceleration frequency composition between the active disk and the bedrock floor has strong correlation,and the composition of soil is different with different frequency.3.Programming and verification of large deformation of strong earthquake surface ruptureBased on the comparison and verification of large-scale model test under the same working condition,the numerical simulation program of large deformation of ground breaking site with strong earthquake is developed.4.Numerical simulation analysis of the ground fault site of strong earthquake(1)Under the action of reverse faults,(I)the smaller the fault dislocation angle,the larger the range and displacement of uneven uplift and uplift area of overburden layer,the worse the fault dislocation of low angle is to the building(II)with the increase of the thickness of the overburden,the uneven settlement position moves to the right with the main fracture zone,and the uneven settlement range of the surface is also expanding,but the surface deformation is relatively more relaxed.(2)The results show that:(I)the influence of the sand clay interbedding on the bottom of the sand clay and pure sand and pure clay sites is not significant;The uneven deformation of sand interbedding in the upper plate area is more synchronous with pure sand site(II)sandy soil within a certain range of the surface can reduce the total deformation range of surface uplift to a certain extent(III)when sand and clay interbedding in the upper plate area,the overall uneven deformation is between the pure clay and the pure sand condition.(3)The simulation analysis of the buildings on the site with high inclination of clay shows that:(I)the upper wall effect is also found in the non free site with buildings.The buildings on the surface of the soil layer have certain influence on the crack extension trace in the overburden(II)under different total height levels,the influence of ground surface fracture zone on the upper and lower buildings under normal fault is about 2:1;Under the reverse fault,it is about 3:1(III)the height of buildings adjacent to the main fracture zone on the upper wall of the two types of faults is significantly related to the difference of foundation displacement,and the rest is not obvious.