膨润土对双轮铣水泥土搅拌墙体强度和渗透特性的影响

Influence of bentonite on the unconfined compressive strength and hydraulic characteristics of cutter soil mixing wall

膨润土浆液常作为地下工程双轮铣水泥土搅拌墙(CSM)的铣削液来改善土体搅拌均匀性和维持槽壁稳定。通过室内试验研究膨润土水泥土试样无侧限抗压强度和渗透系数等特性随膨润土掺入量的变化情况,并结合压汞试验分析掺入膨润土对水泥土微观孔隙特征的影响,探讨掺入膨润土后试样孔隙比的变化与水泥土试样无侧限抗压强度和渗透系数的内在关联。结果表明,掺入膨润土可显著降低水泥固化砂土和粉土的渗透系数;掺入膨润土还能提高无侧限抗压强度,砂土试样的无侧限抗压强度增幅较水泥固化粉土试样更大;固化土无侧限抗压强度和孔隙比与水泥掺量的比值近似呈幂函数关系;膨润土能有效填充孔隙,同时与水泥水化产物发生化学反应,改变水泥土孔隙分布;掺入适量的膨润土可改善水泥土试样承强防渗效果,在固化粉土和砂土试样中膨润土的适宜掺入量分别为5%和2.5%~5%。

Soil-bentonite mixtures are often used to maintain the stability of the deep mixed pile method for the double round milling wall(Cutter Soil Mixing,CSM).The effect of bentonite content on the unconfined compressive strength and permeability of soil-bentonite mixtures in CSM when the local soil was sand and silt.The properties including the unconfined compressive strength and permeability was measured,and microstructure was investigated using MIP.The relationship between the change of pore ratio and the unconfined compressive strength and permeability coefficient of cement soil samples was investigated.The results show that the expansion of the bentonite and chemical reaction with cement hydration products can change the pore distribution of soil-bentonite mixtures;The variation of bentonite content can significantly reduce the permeability coefficient and improve the unconfined compressive strength;The increase of unconfined compressive strength of sand samples is larger than that of silt samples;The ratio of compressive strength to porosity and cement content is approximately a power function relationship;Bentonite can effectively fill the pores,and at the same time,it reacts with cement hydration products to change the pore distribution in cement soil;A certain amount of bentonite is effective in improving the strength of the cement soil sample,but the marginal effect of improving the dosage is not obvious.The optimum content of bentonite in silt is 5%and in sand is 2.5%~5%.