Experimental Study On Seismic Performance Of Rammed Earth Walls In Gansu Area

Raw earth building is still a large number of buildings in rural areas of Western China,especially in poor areas.Its main advantages are local materials,low cost,energy saving and environmental protection,thermal insulation,reusable,construction without environmental pollution,etc,As a result,there are still many inherent deficiencies in the construction of seismic defense capacity of raw soil buildings,which are prone to collapse and cause casualties.In order to effectively improve the overall seismic performance of raw soil buildings,wheat straw and woven bag fiber can be added into raw soil materials to increase the ductility and bearing capacity of buildings.In this paper,a series of researches are carried out on the deformation capacity and ultimate bearing capacity of raw soil wall from the aspects of the situation of rural raw soil houses,the physical and mechanical properties test of raw soil and modified soil,the quasi-static test of bearing wall of raw soil buildings and modified material,and the finite element analysis of raw soil wall.The main work and achievements are as follows:(1)Firstly,the classification of raw soil structure houses and the research status of raw soil wall at home and abroad are summarized.Based on the data and field visit of raw soil structure houses,the main damage forms and existing problems of raw soil structure houses are pointed out and some improvement measures are put forward.(2)A series of physical and mechanical properties tests were carried out on the soil materials used in the raw soil structure house and the reinforced soil with different proportions by adding different proportions of wheat straw and woven bags.The optimal moisture content and maximum dry density of the soil with different admixtures and different proportions were obtained respectively.The compressive strength of the samples made of raw soil materials and modified soil materials were tested respectively The mechanical properties of different soils are obtained by direct shear test and direct shear test.The test results show that the optimal moisture content of raw soil is 16.1%,and the maximum dry density is1.812g/cm3.After reinforcement,the moisture content of raw soil is slightly higher than that of plain soil when the maximum dry density is compacted,and the maximum dry density presents a downward trend with the increase of reinforcement ratio.Reinforced plain soil can improve its compressive strength and shear strength,effectively restrain the deformation of soil,and increase the ultimate load and displacement of plain soil.(3)In this paper,the rammed earth wall is selected as the research object.Six groups of specimens are made,including plain soil and rammed earth wall with different proportions of wheat straw and woven bags.The quasi-static tests are carried out respectively.The failure mechanism,hysteretic curve,skeleton curve,energy dissipation performance,stiffness and stiffness degradation of rammed earth wall under seismic load are obtained.The test results show that,compared with plain soil,the reinforced rammed wall can improve the seismic performance of the rammed wall to a certain extent,improve the energy dissipation capacity and ductility of the rammed wall,and improve the bearing capacity of the wall.(4)According to the failure mode of the rammed wall,the numerical model of the rammed wall is established,and the accuracy of the numerical model is verified by comparing the numerical simulation with the test.The stress development and stress distribution of the rammed wall are analyzed,and the influence of axial compression ratio,height width ratio and other factors on the seismic performance is considered.The results show that a certain vertical load can be used under the condition of no shear compression failure With the increase of wall thickness,the ultimate load increases gradually,but the peak displacement decreases.The research results can provide a certain reference value for the development of rammed earth wall,and provide a low-cost,feasible,green and practical technology for the construction of raw earth houses in rural areas.