Disintegration Characteristics of MICP-treated Granite Residual Soils

doi:10.11988/ckyyb.20231104

Abstract

Abstract:

Granite residual soil is highly absorbent and prone to disintegration in the presence of water, which poses potential safety hazards for engineering construction. Microbial-induced calcium carbonate precipitation (MICP), as a new reinforcement method, can significantly improve the disintegration properties of soils. Disintegration tests were conducted on natural and MICP-treated soil samples with different cementation concentrations, and the disintegration mechanism was analyzed based on X-ray diffraction spectra and scanning electron microscope (SEM) images. Results reveal that the disintegration processes of the natural soil samples can be divided into three stages: surface water absorption and spalling stage, soil softening stage stage, and complete disintegration stage. In contrast, the MICP-treated samples exhibit four stages: forced water intrusion stage, fissure development stage, intense erosion stage, and stable disintegration stage. Under MICP treatment, the disintegration curve of the residual soil transitions from complete disintegration to incomplete disintegration characteristics. With the increase of calcium carbonate content, the disintegration resistance can be obviously enhanced. Calcium carbonate crystals are mainly distributed on sample surfaces, within pores and at contact points, playing crucial roles in encapsulating, filling, and cementing soil particles, which are the main reasons for improving the disintegration characteristics of residual soils. These findings provide valuable references for enhancing the disintegration properties of residual soils in engineering applications.

Key words: granite residual soil, MICP, disintegration properties, mineral analysis, microstructure

CLC Number:

TU431土和地基的应力

CHEN Xin, AN Ran, ZHANG Xian-wei, CHEN Chang, YUAN Tong. Disintegration Characteristics of MICP-treated Granite Residual Soils[J]. Journal of Changjiang River Scientific Research Institute, 2025, 42(2): 138-144.

Figures/Tables 10

Table 1 Basic physical parameters and mineral compositions of soil

含水率/ %	干密度/ (g·cm^-3)	相对密度	孔隙比	液限/ %	塑限/ %	塑性指数
35.2	1.43	2.66	1.03	50.1	25.2	24.9

Fig.1 Particle size distribution curve of granite residual soil

Fig.2 Disintegration device

Fig.3 Calcium carbonate content under varying cementation concentration

Fig.4 Typical morphology of soil disintegration

Fig.5 Curves of soil disintegration

Fig.6 Classification curves of disintegration characteristics

Table 2 Classification of soil disintegration characteristics

类别	等级	符号	崩解形态	崩解曲线特征	试验土样
完全崩解	快速	CDR	局部大块脱落	C_t=100%	素土样
	逐步	CDI	小块土体崩落	阶梯状上升	0.5、1.0 mol/L MICP固化样
	稳定	CDS	片状、块状剥落	光滑平缓上升	1.5 mol/L MICP固化样
不完全崩解	快速	IDR	—	—	—
	逐步	IDI	逐层片状脱落	C_t<100%	2.0、2.5 mol/L MICP固化样
	稳定	IDS	—	—	—

Fig.7 Relations of mineral content and disintegration rate against concentration

Fig.8 SEM images of different samples

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