砂土基MICP土工材料剪切强度试验及可靠性分析

选用巴氏芽孢杆菌,以不同粒径砂土为岩土基质,应用微生物诱导矿化技术生成MICP土工材料试样,自然养护7 d后,应用直剪仪进行了抗剪强度测试试验。结果表明,MICP细砂土内摩擦角范围最大,MICP粗粒砂土内摩擦角范围最小,这与微生物诱导生成的矿化物填充空隙的过程中形成胶结作用有重要的关系,粗粒砂土空隙大,MICP材料强度的增长主要依靠诱导生成的碳酸钙咬合力;中粗砂粒土表面粗糙度的提高有效增强了矿化土工材料的强度;细砂土主要是填充空隙,材料更加密实,导致抗剪强度最大。再运用多项式混沌扩展(PCE)方法建立代理模型,求得其前四阶统计矩,对内摩擦角输出响应的不确定性进行了量化。

Shear Strength Testing and Reliability Analysis on MICP-treated Geomaterial of Sandy Parent Soil

Using sand with different particle sizes as soil matrix, MICP-geomaterial samples were generated through microbial induced mineralization technique. The shear strength of the samples was obtained by means of direct shear test after natural conservation for 7 days. The results show that the internal friction angle scatters in the broadest range for MICP fine sandy soil and in the narrowest range for MICP coarse sand. This is attributed to the cementation of the microbial induced mineralized materials in the soil pore. The strength of the MICP coarse sand soil mainly depends on the interlock of the induced calcium carbonate because this material has a large void. The strength of mineralized geosynthetics enhances effectively with the increase of surface roughness of medium coarse sandy soil. Fine sand has small voids and large density, leading to maximum shear strength. Then an agent model was established using polynomial chaotic extended method. The first four-order statistical moments were obtained. The uncertainty of the output response of the internal friction angle was quantified.