掺加硅灰和石灰条件下的超盐渍土抗剪特征研究

Investigation on shear characteristics of hypersaline soil improved by lime and silica fume

为了揭示石灰和硅灰胶结超盐渍土的抗剪强度规律,对采自宁夏平罗县姚伏镇的超盐渍土分别掺入硅灰和石灰进行超盐渍土固化,其中,硅灰掺量分别为1%、3%、5%,石灰掺量分别为硅灰掺量的20%、40%、60%。并利用三轴仪对7、28 d龄期固化的超盐渍土进行抗剪强度指标测定。试验结果表明:7 d龄期,1%硅灰掺量的固化超盐渍土的摩擦角随石灰掺量的增加呈现先增加后减小的变化趋势,28d龄期,1%硅灰掺量的超盐渍土的摩擦角随石灰掺量的增加而减小;7、28 d龄期,3%、5%硅灰掺量的固化超盐渍土的摩擦角和黏聚力随着石灰掺量的增加而增加。鉴于超盐渍土的抗剪强度由摩擦角和黏聚力共同决定,而随硅灰和石灰掺量的增加,固化超盐渍土的摩擦角和黏聚力的变化趋势不一致,为了易于确定固化超盐渍土中硅灰和石灰土最佳掺量,文中给出了抗剪强度临界深度的判断公式,可依据判别公式来确定硅灰和石灰的最佳掺量。

In order to investigate the mechanical properties of lime and silica fume cemented hypersaline soil,1%,3%,5% silica fume and lime of 20%,40% and 60% of the silica fume were mixed into hypersaline soil from Yaofu,Pingluo,Ningxia,respectively. The shear strength of the stabilized hypersaline soils of 7 d and 28 d age was investigated by a triaxial test. The results show that,at the age of 7 d,when the content of silica fume is 1%,the friction angle of the hypersalinesoil first increased and then decreased with the increase of lime dosage; that,at the age of 28 d,the friction angle decreased with the increase of lime dosage. When the content of silica fume is 3% and5%,the friction angle and cohesion increased with the increase of the lime dosage at the age of 7 d and 28 d,respectively. The shear strength of the hypersaline soil is codetermined by the friction angle and cohesive force,but they have different trends of change with the increase of silica fume and lime. In order to determine the optimal content of silicon fume and lime in stabilized hypersaline soil to increase its shear strength,the critical depth formula is proposed,and the optimal content of the silicon fume and lime can be determined according to the formula.