Experimental Study On Structural And Engineering Mechanical Properties Of Paleosail In Loess Stratum

All the way with China’s western development strategy and "area" the development of major construction projects,construction scale development in the direction of the higher.bigger,deeper,the loess area,more and more engineering construction,and a large number of loess landslide are touched on ancient hydrogels,previous studies on the loess as the main rescarch object,the study of ancient soil is relatively small.In Xi ’an area,Q3 paleosoil lbetween Malan loess and Lishi loess has the characteristics of thickness,integrity,depth of burial and more touching projects compared with other paleosoils.Therefore,this paper takes Q3 paleosoil of different sites in Xi ’an as the main research object,conducts qualitative and quantitative research and analysis on the physical characteristics,microscopic characteristics,initial structural and engineering mechanical characteristics of Q3 paleosoil through relevant tests,and draws the following conclusions:(1)Various physical properties of Q3 paleosoils in different sites were obtained through conventional geotechnical tests;According to the grain size grading curve,the ancient soil was judged to be poorly graded.The permeability of Q3 paleosoil is weak and plays a role of water isolation.According to the free expansion rate and mineral composition,Q3 paleosoil is basically not expansive.(2)X-ray diffraction testing technology was used to determine the mineral composition of Q3 paleosoil,in which the percentage of illite is about 56.6%,quartz 29.3%,plagioclase 6.3%.in addition,the total content of calcite,chlorite and potassium feldspar only accounts for 5.0%of the total minerals;By means of scanning electron microscope,IPP image processing software and BDS,the particle contact mode and pore distribution were qualitatively analyzed,and the number of pore cracks,pore area and element distribution were quantitatively described.(3)Based on different sites in Q3 paleosoil on unconfined compressive strength test,the corresponding formulas are used to get the Q3 paleosoil structure index,and by using composite power-index(CPE)model of the unconfined compressive strength and the relationship between the moisture content of fitting,at the same time analysis the unconfined compressive strength,disturbance,flooding and the degree of structural sensitivity index changing with the moisture content,Finally,the quantitative relationship between the physical property index and the texture index was established by introducing the physical comprehensive quantity,and the calculated value of the method was compared with the measured value of the experiment.It was found that the two values were basically close,indicating that the use of physical property index can accurately calculate the texture index of Q3 paleosoil.(4)By confining compression test on different sites in Q3 paleosoil(undisturbed,remaking samples)compression deformation characteristics of the study,to get the corresponding relation curve and the compressive yield stress and so on,further establish constitutive degree index and compression of the relationship between the yield stress,and get the physical index and compression of the quantitative relationship between yield stress;The compression curves of Q3 paleosoils(undisturbed and remolded)in the same period and different sites were normalized by the normalization method,and the normalized expressions of corresponding curves were given by using CPE model.A structural deformation evaluation and correction method is proposed for Q3 paleosoil,which is verified by an example to further supplement and improve the research on compression deformation characteristics of paleosoil layer.(5)By direct shear test study of ancient soil shear deformation characteristics of sample(the original state,restore),and by using composite power-index(CPE)model function fitting,such as the relationship between the moisture content and dry density and strength index,get the corresponding expressions,and then derive the Q3 paleosoil in the case of known moisture content and dry density calculation of shear strength of expression;The influence of calcareous nodules on shear strength of soil was studied by controlling the content of calcareous nodules.