The red-bed residual soil has the characteristics of high liquid limit, low strength and strong expansion and contraction, which cannot be directly used as filler in the project. Through a variety of modified materials pre-mixing, high-efficiency materials re-mixing, and finally proposed to use quicklime-ash wood fiber as an external mixer to improve it. By carrying out shear test, CBR (California bearing ratio) penetration test, mercury pressure test and scanning electron microscope test on specimens with different dosage, the improvement mechanism of quicklime-ash lignocellulosic fibers on the macro-mechanics and micro-porosity of the soil was analyzed. The results show as follaos. The shear strength and cohesive strength of the modified soil increase and then decrease with the increase of lime dosage, and the optimal dosage of modified soil is 4% ash wood fiber + 4% quicklime. The pore size distribution shows that the proportion of large pores and micropores in the modified soil increases, the medium pores decrease, and the proportion of other pores fluctuates steadily. Based on the electron microscope scanning analysis by PCAS software, the pore space and interlayer fissures of the improved soil are reduced compared with the vegetative soil, and the inter-agglomerate cementation capacity is enhanced and the structure is stabilized.
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Engineering Properties and Microscopic Mechanisms of Composite Admixture-modified Residual Soil in Chishui Red Beds[J].
Science Technology and Engineering, 2026, 26(10): 4066-4077 DOI:10.12404/j.issn.1671-1815.2503169
将试验所用红层残积土初筛,去除碎石、草根杂质,放于烘箱中干燥,质量变化小于0.01 g 时,可认为完全干燥,将烘干土碾碎后过2 mm 筛备用。因赤水气候湿润,土体含水率常常超过最优含水率,因此,设置改良土初始含水率为18.5%、密度为1.8 g/cm3,以研究土体较高含水率下的抗剪强度变化。取过2 mm筛土样,分别掺入粉煤灰、灰木质纤维、木质素磺酸钙、稻草灰、白木质纤维、生石灰制成单掺改良土,具体配比如表2所示,按照密度1.8 g/cm3、含水率为18.5%以静压法制取环刀样,进行快速直剪试验。
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