工程科学与技术2025，Vol.57Issue(6)：163-177,15.DOI:10.12454/j.jsuese.202400788
冻融作用下煤基固废改良黄土路基模型试验研究
Experimental Assessment of Coal-based Solid Waste Improved Loess Model Test Under Freeze-Thaw Action
摘要
Abstract
Objective The influence of cyclic freeze-thaw cycles is identified as a primary factor contributing to the susceptibility of subgrades in loess areas of Northwest China to freeze-thaw deterioration.Frost heave and thaw subsidence are recognized as significant engineering challenges in road construction within cold regions.The quality of the soil composing the subgrade is a crucial factor in determining its vulnerability to freeze-thaw damage.However,the current civil engineering industry in cold regions and road construction projects faces a scarcity of sand,gravel,and other raw materials.Therefore,in loess areas,improved loess as a filler is often the preferred material for road construction.The use of cement,lime,and other inorganic binding materials to improve loess can lead to environmental degradation,while employing microorganisms and other innova-tive materials for enhancement is more costly.Therefore,the present study aims to address the critical issues of the resourceful use of coal gangue and coal gasification coarse slag,as well as ecological environmental protection in Ningxia and surrounding regions,by exploring the potential of their combined utilization.The study focuses on applying coal gangue and coal gasification coarse slag in enhancing loess subgrades,particularly under freezing-thawing and moisture variation conditions,as well as analyzing displacement and the underlying mechanisms governing these pro-cesses.The objective is to mitigate freeze-thaw damage affecting loess subgrades in seasonal permafrost areas,expand the utilization of coal-based solid waste,and provide an innovative approach for reference. Methods The research findings on the mechanical properties of gangue and coal gasification coarse slag-improved loess,along with the pre-test and previous research results,were considered.The study examined three coal-based solid waste improved loess conditions,incorporating 30%or 50%gangue mixing and 15%coal gasification coarse slag mixing.At the same time,vegetal loess and lime-improved loess were established as control groups.Taking the Lanqin Expressway in Gaolan County,Lanzhou as a prototype,an indoor half-span scaled subgrade model was con-structed in the cryogenic test chamber,and three control sections were set within each model.Temperature and moisture sensors were arranged in each control section,and a percentage meter was installed on the top surface of the subgrade to monitor displacement changes.The low-tem-perature test hall simulated the seasonal temperature variations in the study area.The study illustrated the improvement effect and mechanism of gangue and gasification slag-improved loess subgrade filler at both macroscopic and microscopic levels by monitoring temperature,moisture,and displacement variations inside the subgrade under different working conditions during freeze-thaw cycles,and combining the results of SEM electron microscope scanning and CT scanning tests. Results and Discussions The main research content and results were as follows:1)Analysis of the internal temperature variation of the subgrade model indicated that,compared to the plain loess subgrade,the 30%and 50%coal gangue-improved loess subgrades and the 15%coal gasifica-tion coarse slag-improved loess subgrade exhibited a 15%increase in temperature at a depth of 0.1 m.At a depth of 3 m,the minimum recorded internal subgrade temperature increased by more than 16%,and at a depth of 0.5 m,the 15%coal gasification coarse slag-improved loess sub-grade and the 50%coal gangue-improved loess subgrade did not experience a completely frozen moment.This result indicated that the 15%gas-ification slag-improved loess subgrade and the 50%coal gangue-improved loess subgrade demonstrated good thermal insulation performance and temperature stability.2)Analyzing the internal moisture variation of the subgrade model exhibited that,compared to the plain loess subgrade fill,the optimal moisture content of the 30%and 50%gangue-improved loess subgrade fill and the 15%coal gasification coarse slag-improved loess decreased.The moisture content of the three improved loess subgrades indicated that the presence of gangue and gasification slag within the soil of the improved loess subgrade significantly hindered water migration.3)After the freezing and thawing of the three improved subgrade groups under optimal moisture conditions,the maximum frost heave of the 15%coal gasification coarse slag-improved loess subgrade and the 30%and 50%coal gangue-improved loess subgrades decreased by 67%and 59%,respectively.In addition,the maximum thaw settlement decreased by 62%,57%,and 63%,respectively,indicating that the incorporation of 15%coal gasification coarse slag or 30%or more coal gangue significantly reduced the frost heave and thaw settlement deformation of loess subgrades.The findings showed that the inclusion of 15%coal gasification coarse slag or more than 30%coal gangue effectively mitigated the freeze-thaw deformation of loess subgrades.In addition,the efficiency in con-trolling frost heave deformation in these three improved subgrade groups was comparable to that of 4%lime,while their effectiveness in control-ling thaw settlement was even superior to that of 4%lime.4)Microstructural analysis revealed that the addition of coal gangue reduced the poros-ity of the improved loess,decreasing water migration within the subgrade soil during freeze-thaw periods.Similarly,the incorporation of coal gasification coarse slag decreased the free water content within the improved soil,thus lowering the freezing point of the improved loess.The re-duction in heat transfer efficiency within the soil was achieved through different mechanisms,reducing the freeze-thaw deformation of the sub-grade.In addition,thermal conductivity measurements indicated that the thermal conductivity of the 15%coal gasification coarse slag or 30%and 50%coal gangue-improved loess filler was significantly lower than that of plain loess,thus enhancing the thermal insulation performance of coal-based solid waste-improved loess subgrades. Conclusions Based on the results of this research,the use of coal gangue and coal gasification coarse slag to improve loess as a subgrade filler demonstrates significant advantages.Compared to plain loess filler,mixing 50%coal gangue or 15%coal gasification slag in loess can effectively enhance the thermal insulation performance of the subgrade,reduce variations in water content,and decrease the deformation of the subgrade's top surface.In addition,the large quantities of locally available coal gangue and coal gasification slag can compensate for the serious shortage of sand,gravel,and other road construction materials.However,to fully realize these benefits,construction quality must be strictly controlled.Be-fore construction,the proposed coal gangue,coal gasification coarse slag,and loess should undergo comprehensive testing of fundamental physi-cal properties such as grain size,density,and moisture content to ensure that the materials meet design requirements.During construction,the wa-ter content and compaction of the mixed fill must be rigorously controlled to guarantee the overall quality and stability of the subgrade.关键词
冻融作用/煤气化粗渣/煤矸石/黄土/路基模型/水热分布/变形Key words
freeze-thaw action/coal gasification slag/coal gangue/loess/subgrade model/hydrothermal distribution/deformation分类
交通工程引用本文复制引用
武立波,刘惠阳,林战举,杨嘉伟,陈宏信..冻融作用下煤基固废改良黄土路基模型试验研究[J].工程科学与技术,2025,57(6):163-177,15.基金项目
国家自然科学基金项目(41961011) （41961011）
宁夏自然科学基金项目(2024AAC03068) （2024AAC03068）
2023年度宁夏回族自治区留学回国人员创新项目 （）
同济大学岩土及地下工程教育部重点实验室开放基金项目(KLE‒TJGE‒B2302) （KLE‒TJGE‒B2302）
