干湿-冻融循环条件下膨胀土的压缩及渗透特性变化规律_张凌凯.pdf

第 44 卷第 3 期 岩 土 力 学 Vol.44 No.3 2023 年 3 月 Rock and Soil Mechanics Mar.2023 收稿日期：2022-04-14 录用日期：2022-09-27 基金项目：新疆维吾尔自治区水利科技专项资金项目（No.XSXJ-2023-22）；新疆维吾尔自治区自然科学基金杰出青年科学基金项目（No.2022D01E45）；新疆维吾尔自治区寒旱区水资源与生态水利工程研究中心（院士专家工作站）项目（No.2022.C-001）。This work was supported by the Xinjiang Uygur Autonomous Region Water Conservancy Science and Technology Special Fund Project(XSXJ-2023-22),the Natural Science Foundation of Xinjiang Uygur Autonomous Region Outstanding Youth Science Fund Project(2022D01E45)and the Xinjiang Uygur Autonomous Region Cold and Arid Region Water Resources and Ecological Water Conservancy Project Research Center(Academician Expert Workstation)Project(2022.C-001).第一作者简介：张凌凯，男，1987 年生，博士，副教授，主要从事环境岩土工程方面的研究工作。E-mail:xjau_ 通讯作者：崔子晏，男，1992 年生，硕士研究生，主要从事于膨胀土力学特性方面研究工作。E-mail: DOI：10.16285/j.rsm.2022.0524 干湿干湿冻融循环条件下膨胀土的压缩 及渗透特性变化规律冻融循环条件下膨胀土的压缩 及渗透特性变化规律 张凌凯1,2，崔子晏1,2（1.新疆农业大学 水利与土木工程学院，新疆 乌鲁木齐 830052；2.新疆农业大学 新疆水利工程安全与水灾害防治重点实验室，新疆 乌鲁木齐 830052）摘摘 要：要：北疆供水一期工程穿越膨胀土区域，历经多次干湿冻融循环后力学特性衰减严重，易产生渠坡局部浅层滑坡和冻胀破坏等现象。为深入研究其劣化机制，通过干湿冻融循环条件下的压缩试验、渗透试验和 SEM 微观扫描试验，从宏细微观多角度分析其压缩和渗透指标的变化规律。研究结果表明：随干湿冻融循环次数的增加，膨胀土整体压缩性增大，其压缩曲线可分为拟弹性段与拟塑性段；随循环次数的增加，回弹指数呈波动趋势，压缩指数与循环次数呈指数正相关，与细微观裂隙呈线性正相关。黏土颗粒在循环作用下组成“团聚体孔隙填充颗粒”形式的较松散的临时结构，絮凝结构增加，各向异性减少；土样承受竖向压力时，膨胀土孔隙间距减少，压缩性较大；压力超过固结屈服应力时，团聚体颗粒扁角化、极角频率增加、孔隙压密，压缩性逐渐稳定。渗透系数在循环过程中变化分为缓慢、迅速、稳定 3 个阶段；渗透系数在第 5 次循环变化较大，第 7 次循环后逐渐稳定，与循环次数及表面裂隙率呈正相关趋势。渗透系数与各项微观参数的灰色关联度均大于 0.65，微观孔隙率是最主要的影响因素；循环作用下微观孔隙发育明显，形成新渗流通道，渗透系数与微观孔隙率呈线性正相关。关关 键键 词：词：干湿冻融循环；膨胀土；压缩特性；渗透特性；微观机制 中图分类号：中图分类号：TU411 文献标识码：文献标识码：A 文章编号：文章编号：10007598(2023)03072813 Compression and permeability characteristics of expansive soil under drying-wetting-freezing-thawing cycles ZHANG Ling-kai1,2,CUI Zi-yan1,2(1.College of Water Conservancy and Civil Engineering,Xinjiang Agricultural University,Urumqi,Xinjiang 830052,China;2.Xinjiang Key Laboratory of Water Conservancy Engineering Safety and Water Disaster Prevention,Xinjiang Agricultural University,Urumqi,Xinjiang 830052,China)Abstract:The first phase of water supply project in northern Xinjiang crossed the expansive soil area,and the mechanical properties of expansive soil are seriously weakened after repeated drying-wetting-freezing-thawing cycles,which cause local shallow landslide and frost heave damage of the canal slope.To further explore the deterioration mechanism of expansive soil canal slope,the changes of compression and permeability indexes are analyzed from macro-,meso-,and micro-perspectives through the compression test,the permeability test,and the SEM microscopic scanning test under drying-wetting-freezing-thawing cycles.The overall compressibility of expansive soil increases with the increase of drying-wetting-freezing-thawing cycles,and its compression curve can be divided into pseudo-elastic section and pseudo-plastic section.With the increase in the number of cycles,the rebound index shows a fluctuation tendency.The compression index is exponentially positively correlated with the number of cycles,and it is linearly correlated with the meso-micro cracks.Under the action of drying-wetting-freezing-thawing cycle,clay particles form a loose temporary structure of aggregates-pores-filled particles,flocculation structure increases,and anisotropy decreases.When the soil sample is subjected to vertical pressure,the pore spacing of expansive soil decreases,and the compressibility is large.When the pressure exceeds the consolidation yield stress,the aggregate particles become flat,the polar angular frequency increases,the pores are compacted,and the 第 3 期 张凌凯等：干湿冻融循环条件下膨胀土的压缩及渗透特性变化规律 729 compressibility is gradually stabilized.Three stages i.e.,slow,rapid,and stable stages,are identified in variation of permeability coefficient in the cycle process.The permeability coefficient changes greatly in the fifth cycle,and gradually stabilizes after 7 cycles,which is positively correlated with the number of cycles and surface fracture rate.The grey correlation degrees between the permeability coefficient and microscopic parameters are greater than 0.65,and microscopic porosity is the most important influencing factor.Under cyclic action,the microscopic pores develop obviously and form new seepage channels.The permeability coefficient is linearly and positively correlated with the microscopic porosity.Keywords:drying-wetting-freezing-thawing cycles;expansive soil;compression test;permeability test;micro mechanism 1 引 言 北疆供水一期工程主要以输水明渠为主，其中部分渠段通过膨胀土地区，在季节气温交替变化和渠道历年夏季通水、冬季停水的运行方式的共同作用下，随明渠使用年限的增加，历经多次干湿冻融循环后力学特性衰减严重，渠基土逐渐劣化，极易产生滑坡或局部坍塌1-2。渠底局部冻涨、浅层蠕变破坏以及大范围、大面积的滑坡、坍塌严重影响着供水渠道的正常供水，给区域水利建设带来巨大损失。这些工程问题实质上是膨胀土在干湿冻融循环条件下力学性能衰减所致。对于膨胀土在干湿、冻融及干湿冻融耦合循环下作用下所造成的力学特性劣化问题，其本质是微观结构变化的外在反应，许多学者从宏观强度衰减、细观裂隙发育、微观结构特性等方面进行深入研究。时伟3、柯睿4、杨忠平5、Gao6等研究了膨胀土随冻融循环次数增加压缩模量及无侧限抗压强度等指标的衰减情况，认为其原因是冻融循环破坏了土体的内部结构，降低了颗粒间胶结连结，产生了损伤破坏。Chu7、Soltani8、唐朝生9、Chang10、Zhu11等基于室内试验结果，分析了土体干缩裂隙形成的发育过程及机制，认为在干燥过程中引起的基质吸力和土体干缩引起的张拉应力是裂隙形成和发育的主要因素。蔡正银12、Zhu13等通过 CT 扫描技术研究了不同干湿冻融耦合循环次数对膨胀土三维裂隙演化规律的影响，描述了内部裂隙由循环初期浅层分散分布向后期深层汇聚偏