Porosity and bedding controls on bio-induced carbonate precipitation and mechanical properties of shale and dolomitic rocks: EICP vs MICP

Mary C. Ngoma , Oladoyin Kolawole
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Abstract

Biocementation is an emerging field within geotechnical engineering that focuses on harnessing microbiological activity to enhance the mechanical properties and behavior of rocks. It often relies on microbial-induced carbonate precipitation (MICP) or enzyme-induced carbonate precipitation (EICP) which utilizes biomineralization by promoting the generation of calcium carbonate (CaCO3) within the pores of geomaterials (rock and soil). However, there is still a lack of knowledge about the effect of porosity and bedding on biocementation in rocks from a mechanistic view. This experimental study investigated the impact of porosity and bedding orientations on the mechanical response of rocks due to biocementations, using two distinct biocementation strategies (MICP and EICP) and characteristically low porosity but interbedded rocks (shale) and more porous but non-bedded (dolostone) rocks. We first conducted biocementation treatments (MICP and EICP) of rock samples over a distinct period and temperature. Subsequently, the rock strength (uniaxial compressive strength, UCS) was measured. Finally, we analyzed the pre- and post-treatment changes in the rock samples to better understand the effect of MICP and EICP biocementations on the mechanical response of the rock samples. The results indicate that biocementations in dolostones can improve the rock mechanical integrity (EICP: +58% UCS; MICP: +25% UCS). In shales, biocementations can either slightly improve (EICP: +1% UCS) or weaken the rock mechanical integrity (MICP: −39% UCS). Further, results suggest that the major controlling mechanisms of biogeomechanical alterations due to MICP and EICP in rocks can be attributed to the inherent porosity, biocementation type, and bedding orientations, and in few cases the mechanisms can be swelling, osmotic suction, or pore pressurization. The findings in this study provide novel insights into the mechanical responses of rocks due to MICP and EICP biocementations.

生物诱导碳酸盐沉淀及页岩和白云质岩石力学性能的孔隙度和层理控制:EICP 与 MICP
生物加固是岩土工程中的一个新兴领域,其重点是利用微生物活动来增强岩石的机械性能和行为。它通常依靠微生物诱导碳酸盐沉淀(MICP)或酶诱导碳酸盐沉淀(EICP),通过促进岩土材料(岩石和土壤)孔隙中碳酸钙(CaCO3)的生成来利用生物矿化。然而,从机理角度来看,人们对孔隙度和垫层对岩石中生物降解的影响仍然缺乏了解。本实验研究利用两种不同的生物加固策略(MICP 和 EICP),以及孔隙率低但有层间的岩石(页岩)和孔隙率高但无层理的岩石(白云石),研究了孔隙率和层理方向对生物加固引起的岩石机械响应的影响。我们首先在不同时期和温度下对岩石样本进行生物水泥化处理(MICP 和 EICP)。随后,测量了岩石强度(单轴抗压强度,UCS)。最后,我们分析了岩石样本在处理前后的变化,以更好地了解 MICP 和 EICP 生物加固对岩石样本机械响应的影响。结果表明,在白云石中进行生物加固可以改善岩石的机械完整性(EICP:+58% UCS;MICP:+25% UCS)。在页岩中,生物加固既可以略微改善岩石的机械完整性(EICP:+1% UCS),也可以削弱岩石的机械完整性(MICP:-39% UCS)。此外,研究结果表明,岩石中的 MICP 和 EICP 导致生物地质力学改变的主要控制机制可归因于固有孔隙度、生物加固类型和层理方向,在少数情况下,其机制可能是膨胀、渗透吸力或孔隙增压。本研究的发现为了解岩石在 MICP 和 EICP 生物加固作用下的力学响应提供了新的视角。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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