不同养护龄期下凹凸棒土改良黏性土三轴压缩试验研究

随着人们对环境保护的重视,凹凸棒土被越来越多的用于土体改良中。目前研究主要针对凹凸棒土对土壤污染修复、团粒结构和水力参数的影响,缺少对黏性土土体强度特性改善方面的研究。本文通过不固结不排水三轴压缩试验,探究凹凸棒土改良黏性土在不同养护龄期条件下的强度变化规律,结合扫描电镜图像(SEM)对凹凸棒土改良土体的作用机理进行讨论。研究发现,随着凹凸棒土置换量和养护时间的增加,试样的脆性增加,内摩擦角逐渐增大,黏聚力表现出先增加后减小的趋势。凹凸棒土吸附周围土颗粒和水形成的团聚体增加了改良试样内部的滑动摩擦力和咬合摩擦力,从而提升了改良试样的内摩擦角。在团聚体趋于稳定过程中形成的表观黏聚力变化是试样黏聚力先增后降的主要原因。研究结果为凹凸棒土在道路路基工程与边坡防护工程中的应用提供一定的参考依据。

Experimental study on the triaxial compressive properties of attapulgite modified clayey soil under different curing times

From the perspective of environmental protection, attapulgite clay has been introduced for soil improvement. Great efforts have been made to investigate the influence of attapulgite clay on remediation of contaminated soils, aggregate structure and hydraulic parameters, but the discussion on mechanical properties of modified soils is lacked. In this study, unconsolidated undrained triaxial compression tests were conducted to investigate the influence of attapulgite incorporation on the shear strength characteristics of soil under different curing times, coupling with the scanning electron microscopy (SEM) tests to understand its underlying mechanism. It is found that the increase of replacement amount of attapulgite soil and curing time leads to a more brittle behavior of modified soil, which also results to gradually increase of the internal friction angle, and the cohesion will also increase first but then decrease. The aggregates formed by attapulgite adsorbing surrounding soil particles and water increased the inter-particle friction. The change of apparent cohesion formed during the stabilization of aggregates is the main reason for the first increase and then decrease of cohesion. Results of this study may provide reference for application of attapulgite in road engineering and slope protection.