Research On Deformation Characteristics Of Foundation Pit Based On Triaxial Test

The excavation is a process of lateral unloading for foundation pit slope soil.All the time,engineering circles tend to acquire model parameters using conventional triaxial compression test results to analyze the deformation characteristics of foundation pit slope soil.This promptes us to explore a method of test that is consistent with the actual situation.In order to simulate the deformation behavior of foundation pit slope soil,this paper analyzes lateral deformation of foundation pit slope soil by using the shear strength parameters from triaxial unloading condition.It is hoped that research method can provide reference for the reasonable design and construction of foundation pit.（1）According to excavations,the author formulated test plans based on stress path changes of foundation pit slope soil.The author reformed the triaxial apparatus of strain control by reference to the theory of the triaxial apparatus of stress control.The paper performed triaxial unloading test using the modified strain controlled triaxial apparatus,researched deformation characteristics of undisturbed losses samples under triaxial unloading condition,and analyzed differences with conventional triaxial compression test.Test results show:In the triaxial unloading condition,the samples relation curve of（σ₁-σ₃）^ε₁ approached to the ideal elastic-plasticity model,samples appeared obvious elastic deformation in the early stage and the scale of elastic-plastic deformations was small.In the late stage,samples showed distinctive plastic deformations and had high damage speed.When damages happened,samples damage ratio approached to 1,reached ultimate capacity limit states.As a result,intensity decreased fast.And its deformation showed property of strain softening.（2）Compared with conventional triaxial compression test,this test has significant different test parameters and tendency.which are mainly characterized by smaller cohesion,larger internal friction angle and larger initial modulus.So this paper taking engineering practice as example,the influence of slope stability analysis of foundation pit by applying different shear strenth parameters into the FLAC3D software was discussed.The research results show that it has larger deformation to analyze lateral deformation of foundation pit slope by using the shear strength parameters from triaxial unloading condition compared with conventional triaxial compression test.This means that it is safer to guide design and construction of foundation pit slope by using the shear strength parameters from triaxial unloading condition compared with conventional triaxial compression test.In the design of foundation pit,we should analyze the stress path and stress state of soil,and use the test parameters which is accords with actual engineering.Take security and economy into account,so that the excavation and support scheme of foundation pit to be more reasonable.