Experimental Study on Physical-Mechanical Properties of Expansive Soil Improved by Multiple Admixtures

Xiaocheng Huang,Binhui Ma,Chengbin He,Zhuo Li,Qiunan Chen,Kai Cai,Bingchu Chen,Xing Zeng,Zhiyong Hu,Rihong Cao

doi:10.1155/2021/5567753

Xiaocheng Huang, Binhui Ma + Show 8 more

Open Access

https://doi.org/10.1155/2021/5567753

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Abstract

The treatment of expansive soil is always a difficult problem in engineering. Using coal gangue, fly ash, and other solid waste to treat expansive soil has gradually become a new way of energy saving and environmental protection. Most of the existing studies focus on using one or two kinds of admixtures to improve expansive soil, but there are few studies on improving expansive soil with multiple admixtures. In this paper, the expansion and shrinkage deformation and strength characteristics of expansive soil modified by coal gangue, fly ash, and lime are studied experimentally. Nine groups of different mixing schemes were designed through orthogonal tests, and the physical and mechanical properties of the improved expansive soil under different mixing ratios were tested. The sensitivity analysis of the test results was carried out to study the effect of each admixture on the improved expansive soil under different mixing ratios, and the optimal mix ratio under different conditions was obtained. The optimal mix ratio is 8% for coal gangue, 11% for fly ash, and 6% for lime. Further scanning electron microscopy (SEM) tests were carried out to analyze the microstructure of the improved expansive soil and explore the improvement mechanism of the multiadmixture. The results show that the optimal moisture content and the maximum dry density of the expansive soil with ash are decreased, and the properties of liquid plastic limit, free expansion rate, shear strength, and unconfined compressive strength of the expansive soil are improved obviously. Through the analysis of the comprehensive balance method, it is found that the content of lime has the greatest influence on the improvement effect of expansive soil, followed by that of coal gangue, and the least is that of fly ash. SEM structure analysis reveals that the particles of improved expansive soil are mainly aggregates, the soil structure is dense, particle agglomeration increases, and the overall structure is stronger. The research results can provide reference for the improvement of expansive soil with various admixtures and the resource utilization of coal gangue, fly ash, and other solid wastes.

Highlights

Coal gangue is the carbonaceous rock with high ash content and low calorific value associated with coal and is one of the largest industrial solid wastes in China [1]
Gireesh Kumar and Harika [18] used fly ash and other wastes as admixtures, mixed with expansive soil as stabilizer of expansive soil, for testing. e results show that more than 10% fly ash and black cotton soil are recommended to be used as the mixture, which can be used in the construction of paving stones and other foundation projects
The relative volume mass of the admixture is lower than that of plain expansive soil. It has a certain cementing effect, and the new cementing substance reduces the compaction characteristic of the mixed lime soil, which leads to the decrease of dry density

Summary

Introduction

Coal gangue is the carbonaceous rock with high ash content and low calorific value associated with coal and is one of the largest industrial solid wastes in China [1]. Shen et al [9] studied the composite improvement of strong expansive soil with lime, potassium chloride, polyvinyl alcohol, and polypropylene fiber and verified the effectiveness of the improved method by free expansion rate test and shear test. By analyzing gangue content and X-ray diffraction, Yang and Zhang [10] proved that the materials separated from coal gangue could be consolidated with expansive soil or undergo ion exchange reaction to improve the cohesion and shear strength of expansive soil. Qiu [14] studied the characteristics of lime improved expansive soil under dry wet cycle and carried out compaction test, free expansion rate test, crack development test, and consolidation fast shear test. Abbaspour et al [16] modified the expansive soil with the Waste Tire Textile Fibers (WTTFs)

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Results

Conclusion