Research On Mechanical Properties Of Cement Soil In Jingzhou City And Its Applications

Cement-soil mixing piles have been widely used in foundation pit support,soft foundation treatment,etc.The reinforcement effect mainly depends on the mechanical properties of cement-soil.In this paper,the typical silty soil in Jingzhou city area is taken as the object,the cement type,label,cement mixing ratio,age,water-cement ratio are used as experimental variables,and the indoor test and PFC^2Dnumerical simulation are combined to study the mechanical properties of the cement soil in Jingzhou city area.And apply the obtained test results to the design of foundation pit support.Research indicates:(1)Unconfined uniaxial compressive strength test:the strength of cement soil with P·O42.5 cement as the curing agent is greater than that with P·O42.5 cement as the curing agent;The strength can be increased by 14.3%-50.0%;the strength of cement-soil and cement mixing ratio and age are linear functions and exponential functions,respectively,and both increase with the increase of cement mixing ratio and age;the strength of cement-soil increases with the increase of cement mixing ratio and age.The water-cement ratio increases and decreases;the cement mixing ratio and age have an effect on the stress-strain curve and the failure mode.(2)Triaxial compression test:The shear strength index of P·O42.5 cement soil is greater than that of P·O42.5 cement soil;the shear strength index of cement soil with mark 425 is much greater than that of cement soil with mark 325 The shear strength index of soil;the shear strength index of cement soil increases with the increase of cement mixing ratio and age,and decreases with the increase of water-cement ratio,and both show a non-linear relationship;The peak strength increases with the increase of cement mixing ratio and confining pressure,the critical strain increases with the increase of confining pressure,and decreases with the increase of cement mixing ratio;cement mixing ratio and confining pressure It also has an impact on the destruction of cement soil.(3)Numerical simulation is more consistent with the test results;using the test results,based on PFC^2D,the relationship between the meso-parameters and the cement mixing ratio and age function is established.This result can be used to compare the cement-soil with different cement mixing ratios and ages.The compressive strength and shear strength of uniaxial soil are limited to simulation prediction.(4)The test results of this paper and the cement-soil shear index obtained from the foundation pit support specification are used to calculate the foundation pit engineering and compare with the on-site monitoring results.The calculation shows that the calculated results of the selected shear strength indexes in the laboratory test are closer to the actual measured values of the deformation of the foundation pit.