微生物固化风积沙力学特性及细观模拟研究

Mechanical Properties and Meso-Simulation of Micp-Treated Aeolian Sand

风积沙颗粒细小均匀,粒间无黏聚力,其力学特性较差,通过微生物诱导碳酸钙沉淀技术(Microbial-Induced Calcite Precipitation,MICP),可胶结松散土颗粒,改善风积沙的力学特性。采用无侧限抗压强度试验研究微生物固化风积沙的力学特性,并结合扫描电镜及离散元数值模拟方法(Partical Flow Code,PFC^(3D)),从细观角度进行研究。在PFC^(3D)中利用微小颗粒单元与粘结模型模拟碳酸钙晶体,研究颗粒细观力学参数的变化规律。研究结果表明:微生物诱导沉积产生的碳酸钙晶体主要粘附在风积沙骨架颗粒接触部位形成连接键,从而产生胶结作用提高风积沙的力学性能;当风积沙具有较大的初始孔隙率时,MICP固化过程更充分,固化后的风积沙试样孔隙率明显减小,表现出较高的强度特性;同时,碳酸钙含量与风积沙力学性能的提高有较好的关联性。

Aeolian sand particles are small and homogeneous,without cohesion between the particles,and its mechanical properties are poor. Through the technology of microbial induction calcite precipitation(MICP),the loose soil particles can be cemented,improving the mechanical properties of the aeolian sand. The mechanical properties of the microbial solidified aeolian sand were studied by the unconfined compressive strength tests,and combined with the scanning electron microscope(SEM)and the discrete element numerical simulation method by using the Partical Flow Code(PFC^(3D)) software. In the PFC^(3D),the micro-particle element and the bonding model were used to simulate the calcium carbonate crystals,to study the changes of the particle meso-mechanical parameters. The results showed that the calcium carbonate crystals produced by the microbial induced deposition mainly adhered to the contact positions of the aeolian sand skeleton particles to form bonding bonds,generating cementation to improve the mechanical properties of aeolian sand. The MICP curing process was more sufficient when the aeolian sand had a larger initial porosity,and the porosity of the cured aeolian sand specimen decreased obviously after the curing process,showing higher strength characteristics.Meanwhile,the calcium carbonate content had a good correlation with the improvement of the aeolian sand mechanical properties.