木质素改良上海黏土无侧限抗压强度试验研究

Experimental Study on Unconfined Compression Strength of Lignin Modified Shanghai Clay

为改善上海地区黏土颗粒含水率高、强度低的力学特性,采用木质素加固黏土的方法,通过无侧限抗压强度试验和SEM试验,研究了不同木质素掺量、养护温度和养护龄期对木质素固化黏土无侧限抗压强度的影响。试验结果表明:木质素磺酸钠能够增强上海黏土的无侧限抗压强度;随木质素掺量的增大,黏土无侧限抗压强度先增大后减小,存在最优掺量值。不同养护温度下最优掺量不同,养护温度为25℃、-15℃、101℃时试样木质素最优掺量分别为8%、2%、8%。养护温度对黏土试样无侧限抗压强度影响显著。木质素掺量一定时,在一定范围内黏土无侧限抗压强度均随着养护龄期增长而增大,然而101℃养护温度下由于水蒸气逸出和裂隙通道不断发展,14 d后黏土无侧限抗压强度开始下降。SEM试验分析表明,木质素能够加固上海黏土,一方面因为木质素水溶液与土体反应生成的胶黏性物质将土颗粒联结成整体;同时填充了孔隙,改善了土体级配,使土体更加密实。

In order to improve the mechanical property of clay with high water content and low strength in Shanghai area,this paper adopts the method to improve clay with lignin,the effect of different lignin contents,curing temperatures and curing ages on unconfined compression strength of lignin solidified clay are analyzed by unconfined compression strength test and SEM test.The experimental result are as follows.Sodium lignosulfonate can increase its unconfined compression strength of Shanghai clay.With the increase of lignin content,the unconfined compression strength of the clay increases at first and then decreases and there is an optimal content value.The optimal amount of lignin is different at different curing temperatures.When the curing temperature is 25℃,-15℃and 101℃,the optimal amount of lignin is 8%,2%and 8%.Curing temperature has a significant effect on the unconfined compression strength of clay samples.When the amount of lignin is constant,within a certain range the unconfined compression strength of clay increases with curing age,while due to the escape of water vapor and the continuous development of crack channels the unconfined compression strength of the clay began to decrease after 14 days of high temperature curing.SEM test analysis shows that lignin can reinforce Shanghai clay mainly because the adhesive material generated by the reaction of lignin and soil connects the soil particles into a whole,while filling the pores and making the soil more compact.