Stress-Strain Analysis And Numerical Simulation On The Cement Stabilized Soil Of Diaphragm Wall

Cement mixing piles are often in a certain confining pressure environment as a retaining structure or diaphragm wall. The triaxial compression tests of cement stabilized soil can be more fitting to consider the actual pressure environment during its work. Thus, study on the mechanical properties of cement by using triaxial compression tests has very important practical significance.The subject based on the third-lane shiplock's excavation of Shiqiao, Yangzhou. Selecting two kinds of the soil from the project (silty clay and silty sand), preparing a large number of cement-soil samples to carry out the triaxial compression tests. The cement ratio, curing age, moisture content, confining pressure and other factors, which can affect the mechanical properties of cement-soil, are mainly considered in the test. According to the test results, the cement stabilized soil stress-strain law was given. Simulating the stress and deformation of diaphragm wall during the excavation in Shiqiao third-lane shiplock project by the application of finite element software.The main achievement and conclusions can be given as follows:1. Testing cement-soil samples in different cement ratio, different curing ages, different moisture content, different confining pressure and different kind of soil by triaxial compression tests. Analysing the effect of various factors on stress-strain relationship of cement-soil systematically, summing up the variation of cement-soil stress-strain relations.2. The stress-strain curve of cement-soil show that the characteristics of samples have been changed from plastic to brittle with the cement ratio increased; elastic and brittle characteristics of the sample have been performanced significantly with the growth of curing age; different soil particles contained in original soil fundamentally affected the characteristics of cement-soil stress-strain relationship; the samples'plastic characteristic have been performanced significantly with the increase of confining pressure, and the residual strength improved with increasing of confining pressure.3. The shear strength results of cement-soil show that the relationship between shear strength and cement ratio is roughly linear growthing; the early strength of cement-soil increased rapidly in curing; the relationship between shear strength and curing period increased logarithmically; with moisture content growth from 20%, 25% to 30%, the shear strength of samples increases gradually; intensity ratio between silty sand sample and silty clay sample is in 1.02 ~ 1.31; in the situation of low cement ratio and shorter curing, confining pressure was significantly affected the growth of shear strength.4. Analysis the deformation modulus of cement-soil, we can find that deformation modulus of cement soil growth with the increasing of cement ratio, and it growth slowly in the situation of low cement ratio; while the curing age T=28d, the deformation modulus of sample can averagely reach to about 75% of T=90d's.5. Value c increased hundreds of times than before; there is also a large growth in value? , it averagely increased to 32.5°; there are two ways of general performances, hardening and softening in the cement-soil stress-strain curves; samples damage in the form of brittle shear failure, brittle crack failure and plastic shear failure.6. Problems such as initial stress field, element contact, large deformation, etc. can be well considered by using finite element software.And the element Birth/Death function can simulate the excavation works successfully.7. From the simulate result we know that diaphragm wall show obvious regularity in its deformation. The deformation trend may provide reference on estimating deformation and stability of pit slope.8. The stress results of wall show that the stress distribution is corresponded to the deformation. The wall was under the small stress level during the excavation. The bottom of wall moved gradually to the inside of pit, and deflected a little to the outside pit.9. Using the triaxial compression test results of cement-soil as the parameters during the FEM calculation. The simulated results are very close to the measured results in displacement trends and the value range. It can reflect the actual project and provide practical reference for engineering analys.