MICP对钙质砂单颗粒的破碎行为影响研究

Study on the Effect of MICP on the Crushing Behavior of Calcareous Sand Particles

作为一种特殊的岩土介质材料,钙质砂具有在低压下易破碎的性质。微生物诱导方解石沉淀(MICP)技术得到了广泛的关注和认可,可用来改善钙质砂的破碎特性。文章从室内试验和离散元模拟两个角度分别对钙质砂颗粒MICP固化前后进行单颗粒压碎试验,通过Weibull分布和SEM扫描等探究了MICP对钙质砂颗粒破碎行为的影响。结果表明:离散元模拟得到的生存概率曲线及Weibull模量m值与试验结果均吻合较好,验证了该数值模型的有效性。与室内试验相比,数值模拟可以精确地反映颗粒的裂纹分布及破碎过程,且可以研究同一颗粒MICP固化前后的情形,弥补了室内实验的不足,但其取决于模型参数的选取;经过MICP固化后的钙质砂颗粒表面有明显的方解石结晶生成,颗粒表面及内孔隙分别得到一定程度的包裹和填充,导致颗粒破碎强度有明显的增强且离散性大大降低,破碎模式由"多峰型"向"单峰型"转变,局部裂纹减少,多以表面磨损和直接产生贯穿裂纹为主。

As a special geotechnical material, calcareous sand is easy to break under low pressure. In recent years, microbially induced calcite precipitation(MICP) technology has gained wide attention and recognition, which can be used to improve the crushing characteristics of calcareous sand. In this paper, the single particle crushing test of calcareous sand particles before and after MICP was carried out through two aspects of laboratory test and discrete element model simulation, respectively. The effects of MICP on the crushing behavior of calcareous sand particles was investigated through Weibull distribution and SEM scanning. The results show that the survival probability curve and the value of Weibull modulus m obtained by discrete element model simulation are in good agreement with the experimental results, which verifies the validity of the numerical model. Compared with the laboratory test, numerical simulation can accurately reflect the crack distribution and crushing process of the particle as well as studying the situation before and after MICP for the same particle, which makes up the deficiency of the laboratory test. However, it depends on the selection of model parameters.After MICP, calcareous sand particles have obvious calcite crystal formation on its surface, and the surface and internal pores of the particles are wrapped and filled to a certain extent, respectively, resulting in significantly enhanced particle crushing strength and greatly reduced discreteness, and the crushing mode changes from “multi-peaks type” to “single-peak type”, as well as local crack reduction,mainly surface abrasion and direct generation of through-wall crack.