初始含水率对MgO碳化粉土强度和电阻率的影响  

Influence of Initial Water Content on Strength and Electrical Resistivity of MgO-carbonated Silt

作　　者：蔡光华 刘松玉[2,3] 曹菁菁[2,3] 

机构地区：[1]南京林业大学土木工程学院,江苏南京210037 [2]东南大学岩土工程研究所,江苏南京210096 [3]东南大学江苏省城市地下工程与环境安全重点实验室,江苏南京210096

出　　处：《中国公路学报》2017年第11期18-26,共9页China Journal of Highway and Transport

基　　金：国家自然科学基金项目(51279032;41330641);"十二五"国家科技支撑计划项目(2012BAJ01B02-01);国家重点研发计划项目(2016YFC0800201);江苏省普通高校研究生科研创新计划项目(KYLX_0147)

摘　　要：为研究初始含水率对活性MgO碳化固化粉土强度和电阻率的影响,通过室内试验测试分析初始含水率对MgO碳化固化粉土应力-应变、无侧限抗压强度、电阻率、pH值和电导率的影响规律;讨论MgO碳化固化粉土无侧限抗压强度和电阻率间的相互关系;最后通过扫描电镜的微观测试,阐明强度和电阻率的变化机理。研究结果表明:随着初始含水率的增加,碳化试样呈现由脆性向塑性的发展趋势;无侧限抗压强度随初始含水率减小或碳化时间增加而增加;变形模量与无侧限抗压强度的比值为60~200;MgO固化粉土的电阻率随含水率增加呈幂函数递减,且碳化后的电阻率明显高于碳化前的电阻率;在特定碳化时间下强度与电阻率存在较好的线性关系,且电阻率法可作为一种简单、有效的方法来预测MgO碳化固化土的强度;碳化土的pH值和电导率均随初始含水率增加呈先减小后增加的趋势,在初始含水率为20%或25%处达到最小,且碳化时间越长,pH值和电导率越小;MgO碳化固化土中存在有棱柱状的水碳镁石晶体和片状的球碳镁石/水菱镁石晶体,这些碳化产物是导致含水率减小以及干密度、强度和电阻率增加的主要原因。To investigate the influence of the initial water content on the strength and electrical resistivity of MgO-carbonated silt,the effect law of the initial water content on the stress-strain,unconfined compressive strength,electrical resistivity,water content,soil pH and electrical conductivity of pore fluid was analyzed by a series of laboratory tests.The correlation between unconfined compressive strength and electrical resistivity was discussed as well.Finally,based on the microscopic test of scanning electron microscopy（SEM）,the evolution mechanism of strength and electrical resistivity was clarified.The results indicate that the samples tend todevelop from brittleness to plasticity with the increase of the initial water content.Unconfined compressive strength increases with the decrease of the initial water content or the increasing carbonation time.The ratio of deformation modulus to the unconfined compressive strength is about 60-200.The electrical resistivity of MgO-stabilized soil declines with the increase of water content by the power function,and the electrical resistivity of MgO-stabilized silt after carbonation is significantly higher than that before carbonation.The strength and electrical resistivity present a good linear relationship under the specified carbonation time,and hence the electrical resistivity can be used as a simple-effective method for predicting the strength of carbonated soil.With the increasing initial water content,both soil pH and electrical conductivity tend to decrease first and then increase,and reach the minimum at the initial water content of 20% or 25%.The longer the carbonation is,the smaller the soil pH and electrical conductivity are.Moreover,according to the microscopic analysis,it is apparent that the elongated prismatic nesquehonite and flaky dypingite or hydromagnesite exist in carbonated MgO-stabilized soil,and such carbonation products are the main reason for the reduction of water content as well as the increase of dry density,strength and electrical resistiv

关 键 词：道路工程 氧化镁 初始含水率 碳化 无侧限抗压强度 电阻率 

分 类 号：U416[交通运输工程—道路与铁道工程]