Study On The Influence Of In-plane Shock Loss On The Out-of-Plane Performance Of Raw Earth Block Walls

With its advantages of ecological protection,local materials,simple technology and low cost,soil structure is widely distributed and will exist for a long time in the west of China,especially in the economically underdeveloped areas.For the Xinjiang region with frequent seismic activities,due to the low strength of raw soil structural materials,poor structural integrity and weak seismic performance,the plane is the weak link of seismic fortification in rural areas.In this thesis,the phenomenon of out-of-plane collapse of raw earth block wall is common in previous earthquake disasters,and the influence law of the out-of-plane failure characteristics,force model and in-plane shock loss on the out-of-plane performance of raw earth block wall is not clear.The influence research of in-plane shock loss on the out-of-plane performance of raw earth block wall is carried out,and combined with the test results,the force analysis and influence factor extension analysis of the wall are carried out.The main work and conclusions are as follows:（1）In order to explore the failure phenomenon and strength of raw masonry during bending and tensile strength,a two-point bending test along the through joint was carried out on raw masonry,and it was found that the brittle failure occurred along the ash joint within 1/3 of the span during bending and tensile strength of raw masonry,and the bending and tensile strength of the brick masonry was 0.147MPa.The formula for calculating the bending and tensile strength was used for reference.The formula parameter k₄ applicable to raw masonry is 0.1.（2）In order to explore the influence of surface internal shock loss on the out-of-plane performance of raw soil block walls,the out-of-plane airbag loading test was carried out on raw soil block walls with no damage,slight damage and moderate damage.The results showed that:1)The bending and tensile damage of the horizontal through joint extending along the bottom ash joint occurs in the wall,which is manifested as the detachment of the tensile side of the wall from the ground beam and the crushing of the mud on the compression side.The bottom strengthening should be considered in the actual project;The internal seismic damage reduces the section strength and changes the weak parts,and the wall has the tendency of bending and shear failure.However,due to the small ratio of height to width and height to thickness,the bottom bending and tensile failure still occur.2)The out-of-plane loads of the three walls with different damage degrees all show the characteristics of"cracking is peak".The shear oblique cracks formed by in-plane seismic damage reduce the strength of the central section of the wall,weaken the out-of-plane bearing capacity and deformation capacity of the raw soil block wall,accelerate the out-of-plane stiffness degradation rate of the wall,and reduce the out-of-plane bearing capacity of the wall by 6.25%～34.87%.（3）In order to verify the effectiveness of steel mesh cement mortar cladding constraints on the out-of-plane performance of raw soil block walls,the out-of-plane airbag loading tests were carried out on the covered restrained walls with slight and moderate damage.The results show that the cladding constraints improve the internal stiffness,bearing capacity and energy dissipation capacity of raw soil block walls,and the bearing capacity of raw soil block walls with the same horizontal displacement is increased by 30%compared with that of unrestrained raw soil block walls.Due to the constraints of cladding,the wall root has no anchoring,and the strength of the bottom section is weaker than other sections.The bottom shear slip failure occurs under horizontal load,and the bearing capacity of the wall with cladding constraints is reduced by 9.7%compared with that of the unconstrained wall.（4）In order to explore the influencing factors and rules of the out-of-plane performance of raw soil block wall,on the basis of establishing the nondestructive wall force model to clarify the influencing factors,ABAQUS numerical simulation software was used to conduct the parameter expansion analysis of influencing factors.The research shows that:The main factors affecting the out-of-plane bearing capacity of raw soil block walls are mud compressive strength,wall height-width ratio,height-thickness ratio and compressive stress,etc.Changing the wall height-width ratio,height-thickness ratio and compressive stress have little effect on the out-of-plane failure mode and deformation characteristics of raw soil block walls,but have a greater effect on the plastic damage range and damage degree of the wall.The increase of height-thickness ratio or height-width ratio can reduce the out-of-plane bearing capacity of the wall,and the change of wall thickness has a greater effect on the out-of-plane bearing capacity of the wall.The increase of compressive stress can enhance the external bearing capacity of the wall,but the increase is small.