EICP改良膨胀土的物理力学性质试验研究

Experimental study on physical and mechanical properties of expansive soil improved by EICP

为了探究脲酶诱导碳酸钙沉淀(EICP)技术改良弱膨胀土的物理力学特性,利用大豆脲酶开展EICP技术处理弱膨胀土的膨胀特性和力学特性试验研究。通过EICP多因素配比正交试验研究脲酶浓度、初始Ca^(2+)浓度、酶胶比、尿钙比、养护时间对膨胀土碳酸钙生成率、自由膨胀率的影响及其变化规律,确定了EICP反应液最佳配比。采用不同掺量EICP反应液改良膨胀土,通过无荷载膨胀率试验、无侧限抗压强度试验及三轴压缩试验验证改良效果。结果表明:EICP反应液掺量为20%时抑制膨胀土膨胀性效果最好,且此时土体力学强度和碳酸钙生成率最高。大豆脲酶诱导产生的沉淀物为方解石型碳酸钙,附着在土颗粒表面既填充了土颗粒孔隙,也胶结了土体骨架颗粒,阻碍土体与水分接触,提高了土体密实性和黏结强度,改善了膨胀土膨胀性和力学性能。

In order to explore the physical and mechanical properties of weak expansive soil improved by urease Enzyme-Induced Calcium Carbonate Precipitation(EICP) technique,the expansion characteristics and mechanical properties of weak expansive soil treated by EICP were tested by soybean urease.The effects of urease concentration,initial Ca~(2+) concentration,enzyme-binder ratio,urine-calcium ratio and curing time on the formation rate of calcium carbonate and free expansion rate were studied by orthogonal test of EICP multi-factor ratio,and the optimum ratio of EICP reaction solution was determined.On this basis,the expansive soil was improved by different dosages of EICP reaction liquid,and the effect was tested by free expansion rate test,unconfined compressive strength test and triaxial compression test.The results show that when the content of EICP reaction solution is 20%,the inhibiting is the best,and the mechanical strength and calcium carbonate formation rate of soil are the highest.The precipitate induced by soybean urease is calcite calcium carbonate,which is attached to the surface of soil particles.It not only fills the pores of soil particles,but also cements the skeleton particles of soil,hinders the contact between soil and water,improves the compactness and bonding strength of soil,and finally improves the expansibility and mechanical properties of expansive soil.