孙萌萌, 武立波, 杨秋宁, 李宏波, 刘惠阳, 杨嘉伟

(宁夏大学 土木与水利工程学院,宁夏 银川 750021)

引用格式:

孙萌萌, 武立波, 杨秋宁, 等. 煤矸石改良黄土的力学和抗冻融性能[J]. 中国粉体技术, 2024, 30(2): 24-35.

SUN M M, WU L B, YANG Q N, et al. Mechanical and freeze-thaw resistance properties of loess improved by coal gangue[J].China Powder Science and Technology, 2023, 30(2): 24-35.

收稿日期: 2023-07-10,修回日期:2023-11-20,上线日期:2024-01-13。

基金项目:国家自然科学基金项目,编号:41961011;宁夏重点研发计划(引才专项)项目,编号:2019BEB04010。

第一作者简介:孙萌萌(1997—),男,硕士生,研究方向为煤基固废的资源化利用。 E-mail: 562994064@qq.com。

通信作者简介:武立波(1978—),女(满族),副教授,博士,硕士生导师,研究方向为环境岩土工程及煤基固废的建筑资源化利用。E-mail: wulibo@nxu.edu.cn。

摘要: 【目的】提出用煤矸石改良黄土的解决方案,解决煤矸石存量逐年增大且利用率低、 季冻区黄土地基病害严重的双重难题。 【方法】分析煤矸石改良黄土的反应机制,通过无侧限抗压强度、 直剪、 固结压缩和湿陷性试验,分析煤矸石改良黄土试件的无侧限抗压强度、 抗剪强度、 黏聚力、 内摩擦角、 压缩系数和湿陷系数等力学性能指标,确定煤矸石的最优掺量;以黄土原料为对照组,将最优掺量的煤矸石改良黄土试件进行冻融循环试验,再次进行无侧限抗压强度和直剪试验,分析冻融循环后最优试件的力学和抗冻融性能。 【结果】当煤矸石质量分数为 20%,养护龄期 28 d 时,煤矸石改良黄土的无侧限抗压强度为 585 kPa,抗剪强度为 287 kPa,压缩系数约为 0. 19 MPa^-1,黏聚力为 63. 755 kPa,内摩擦角为29. 646 °,湿陷性完全消除;进行冻融循环试验后,随着冻融循环次数的增大,无侧限抗压强度逐渐减小,冻融循环次数为 11 时的无侧限抗压强度、 抗剪强度、 黏聚力损失率分别为 26. 9%、 7.4%、 18. 6%,内摩擦角变化较小,煤矸石改良黄土的力学和抗冻融性能较好。 【结论】煤矸石活性较低,改良后的黄土的强度虽然提升幅度不大,但能明显改善黄土的湿陷性和抗冻融性能,因此煤矸石改良黄土适合作为季节性冻土区黄土的地基材料。

关键词: 煤矸石; 改良黄土; 力学性能; 抗冻融性能

Abstract

Objective Loess with large pores is easy to sink after immersion, and its mechanical properties are easy to change under the action of freeze-thaw cycles, which seriously affects the strength and stability of soil. In seasonal frozen soil area, the use of coal gangue to improve loess can not only reduce the cost, but also solve the problems of large coal gangue pile, wide distribution and environmental pollution. Moreover, the use of coal gangue to improve loess can realize the resource utilization of industrial solid waste, and reduce the cost of engineering construction, while taking into account the problem of environmental protection.

Methods The particle size and composition of loess and coal gangue were tested to analyze the reaction mechanism of coal ganguemodified loess. The unconfined compressive strength test, direct shear test, consolidation compression test and collapsibility test were carried out on the modified loess of coal gangue with different mass fractions. By analyzing the unconfined compressive strength, shear strength, cohesion, internal friction angle, compression coefficient and collapsibility coefficient of coal gangue improved loess specimens, the optimum mass fraction of coal gangue was determined. Using loess raw material as control group, the freeze-thaw cycle test of coal gangue with optimum mass fraction was carried out. To analyze the mechanical properties of the optimal specimens after freeze-thaw cycle, the unconfined compressive strength test and direct shear test were carried out.

Results and Discussion When the mass fraction of coal gangue is 20% and the curing period is 28 days, the unconfined compressive strength of the improved loess is 585 kPa, the shear strength is 287 kPa, the compression coefficient is about 0. 19 MPa^-1,the cohesion of the improved loess is 63. 755 kPa, the internal friction angle is 29. 646 °, and the collapsibility is eliminated.The reaction between coal gangue and loess is sufficient, and the cementation between the reaction products and soil particles is strengthened. Meanwhile, the reaction products fill the pores of loess, making the soil structure more dense. In the freeze-thaw cycle test of the optimum specimen with 20% coal gangue, the unconfined compressive strength of the optimum specimen decreases gradually with the increase of the number of freeze-thaw cycles. When the number of freeze-thaw cycles is 11, the loss rates of unconfined compressive strength, shear strength and cohesion are 26. 9%, 7. 4% and 18. 6%, respectively. In contrast, the loss rates of unconfined compressive strength, shear strength and cohesion of unimproved loess are 35. 8%, 9. 6% and 24. 3%, respectively. The influence of freeze-thaw cycles on internal friction angle is small. Therefore, coal gangue-modified loess has better freeze-thaw resistance.

Conclusion Although the activity of coal gangue is low and the strength of improved loess slowly, the collapsibility and freeze-thaw resistance of coal gangue improved loess can be significantly improved. Therefore, when coal gangue is added into loess, the strength and the freeze-thaw resistance of loess can be improved and the collapsibility of loess can be eliminated. In conclusion,coal gangue improved loess is suitable as a foundation material of loess in seasonal frozen soil area.

Keywords:coal gangue; improved loess; mechanical property; freeze-thaw resistance

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