考虑渗透系数变化的MICP加固钙质砂抗液化特性数值模拟研究

我国南海地区的吹填造陆和岛礁建设面临诸多挑战,如钙质砂材料面临的地基液化风险,微生物诱导碳酸钙沉淀技术为其(MICP)提供新的解决思路。该文进行考虑渗透系数变化的MICP加固钙质砂场地的两相流数值模拟分析,结果表明,随着加固次数的增加,胶结液的扩散范围从加固3次后的20倍管径增大到加固6次后的34倍管径,加固范围增大速率逐渐减慢,呈现“下大上小”的梯形状。采用微生物加固技术有效提高钙质砂场地的抗剪强度和抗液化能力,加固后土体强度、地基的剪应力大幅增加,超孔压比、地表沉降、水平位移和剪应变分别下降39.37%、36.61%、42.27%和41.17%。不考虑渗透系数变化的工况模拟结果偏差均在7%以上,因此不能忽略MICP加固过程中渗透系数的变化。

The construction of dredged land and islands and reefs in the South China Sea region of China faces many challenges,such as the foundation liquefaction risk faced by calcareous sand materials.Microbially Induced Carbonate Precipitation(MICP)technology provides new solutions.A numerical simulation analysis of two-phase flow in a calcareous sand site reinforced by MICP was carried out taking into account the change of permeability coefficient.The results show that with the increase of reinforcement times,the diffusion range of cement liquid increases from 20 times the pipe diameter after three reinforcement times to 34 times the pipe diameter after six reinforcement times.The rate of increasing the reinforcement range gradually slows down,showing a ladder shape of"big down and small up".The use of microbial reinforcement technology has effectively improved the shear strength and liquefaction resistance of the calcareous sand site.After reinforcement,the soil strength and the shear stress of the foundation have greatly increased,and the excess pore pressure ratio,surface settlement,horizontal displacement and shear strain have decreased by 39.37%,36.61%,42.27%and 41.17%respectively.The deviation of simulation results without considering the change of permeability coefficient is more than 7%,so the change of permeability coefficient during MICAP reinforcement cannot be ignored.