不同含石量条件下砂卵石土特性试验研究

Experimental Studies on Properties of Sandy Pebble Soil With Different Stone Content

砂卵石地层是一种典型的力学不稳定地层,盾构在此类地层施工中常遇到出土困难、刀盘磨损和地下水喷涌等问题.针对此类地层物质组成和结构的复杂多变性,选择洛阳地铁2号线某站点附近砂卵石地层进行取样,进行不同含石量下砂卵石土的大型直剪试验、坍落度试验和渗透试验,系统地研究了含石量对砂卵石土抗剪强度、流动性和渗透性的影响.试验结果表明:砂卵石土抗剪强度和内摩擦角均随着含石量的增加而呈非线性增大,且含石量小于30%时抗剪强度和内摩擦角增大较小,含石量位于30%～70%时抗剪强度和内摩擦角增大显著,含石量大于70%时抗剪强度和内摩擦角变化不明显;砂卵石土坍落度随着含石量增大而减小,且存在一个减小速率明显不同的分界含石量约为50%;砂卵石土渗透系数随着含石量的增加而增大,且表现出与抗剪强度和内摩擦角一致的规律.

Sandy pebble stratum is a kind of typical mechanical instability stratum.Shield tunneling often en-countered difficulties such as unearthed difficulties,cutter disc wear and groundwater gushing.Aiming at the complex variability of the material composition and structure of this kind of stratum,sandy pebble soil sampling are selected in Luoyang Metro Line 2,and the properties of sandy pebble soil under different stone content are studied by using large direct shear test,slump test and permeability test.The results show that the shear strength and internal friction angle of sandy pebble soil increase nonlinearly with the increasing of stone content,and the shear strength and friction angle increase slow when stone content is less than 30%.The shear strength and internal friction angle increase significantly when the stone content is 30%~70%,and the shear strength and the internal friction angle are not obviously changed when the stone content is more than 70%.The slump of sandy pebble soil decreases with the increasing stone content and a demarcation rate of about 50%of the stone content is found.The permeability coeffi-cient of sandy pebble soil increases with the increasing stone content and shows a similar rule like the shear strength and the internal friction angle.