桂林地区酸 、碱污染红黏土力学效应弱化试验研究

为了研究酸、碱污染对红黏土力学性质的影响,分别使用酸(HCl)溶液和碱(NaOH)溶液对桂林雁山红黏土进行浸泡,考虑酸浓度(0、1%、4%、8%)和养护时间(7,14d),碱浓度(0、4%、8%、12%)和养护时间(7,14d)双因子因素,通过室内试验,包括固结试验、三轴试验(UU)和直剪试验(快剪),分析酸碱污染对桂林雁山红黏土压缩性指标和抗剪强度指标的变化。试验结果表明:1)红黏土在HCl和NaOH中浸泡后,其压缩模量、黏聚力与内摩擦角逐渐减小,且随着酸、碱浓度及养护时间增加,减小的幅度增大;2)对比经HCl和NaOH浸泡红黏土,在相同养护时间下,经HCl浸泡红黏土的压缩模量、黏聚力的变化程度大于经NaOH浸泡红黏土的变化,内摩擦角反之;3)随着养护时间增加,经HCl浸泡的红黏土黏聚力与内摩擦角的变化程度小于经NaOH浸泡红黏土的变化,压缩模量反之。对试验结果分析后认为:在酸碱溶液作用下,红黏土的化学成分、颗粒大小及形状都将发生变化,使其原本稳定的结构状态发生改变,导致桂林地区酸碱污染红黏土力学效应弱化。

Experimental study on the weakening of mechanical properties of red clay contaminated by acid and alkali in Guilin area

In order to study the effect of acid and alkali pollution on the mechanical properties of red clay, laboratory tests (consolidation test, triaxial test (UU) and direct shear test (quick shear)) have been carried out of the red clay of Yanshan, Guilin, and the samples are soaked in acid solution (HCl) and alkali solution (NaOH), respectively, to get the changes of compressibility index and shear strength index of the red clay by acid and alkali pollution. Two factors, the concentration of both acid(0,1%, 4%, 8%) and alkali (0,4%, 8%, 12%) and the same curing time (7 d, 14 d) were taken into account. The results show that:1)the compression modulus, cohesive force and internal friction angle of red clay soaked in HCl or NaOH gradually decreased, and the extent of which became greater with the increase of acid or alkali concentration and curing time;2)under the same curing time, the degree of change of compressive modulus and cohesion of the red clay soaked in HCl is more significant than that of the red clay soaked in NaOH, and the case was just the opposite in terms of the internal friction angle;3)with the increase of curing time, the cohesion and internal friction angle of red clay soaked in NaOH has greater degree of change than that of the red clay soaked in HCl, and the case was just the opposite in terms of the compression modulus. The analysis of the test results indicate that the chemical composition, particle size and shape of red clay will be changed under the action of acid and alkali solution, which will bring changes to the original stable structure state and weaken the mechanical effect of red clay in Guilin area.