单向冻结粉质黏土已冻区分凝冰分布规律试验研究  

Experimental study on segregating ice cracks distribution characteristics in unidirectional frozen silty clay

作　　者：王震[1] 朱珍德[2,3] 胡家豪 周子玉 WANG Zhen;ZHU Zhen-de;HU Jia-hao;ZHOU Zi-yu(Department of Civil and Environmental Engineering,Shantou University,Shantou,Guangdong 515063,China;Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering,Hohai University,Nanjing,Jiangsu 210098,China;Jiangsu Research Center for Geotechnical Engineering Technology,Hohai University,Nanjing,Jiangsu 210098,China)

机构地区：[1]汕头大学土木与环境工程系,广东汕头515063 [2]河海大学岩土力学与堤坝工程教育部重点实验室,江苏南京210098 [3]河海大学江苏省岩土工程技术工程研究所,江苏南京210098

出　　处：《岩土力学》2024年第2期407-416,432,共11页Rock and Soil Mechanics

基　　金：国家自然科学基金(No.41831278);汕头大学科研启动基金(No.NTF21015)。

摘　　要：在单向冻结中,已冻区分凝冰的产生和发展是影响冻融土结构性特征的重要因素。选取降温速率(0.5~0.005℃/s)、冷端温度(–30~–70℃)、暖端补水(无补水、恒压补水)等3种单向冻结边界条件,探究其对已冻区分凝冰发育的影响规律。基于光学显微数字拍摄,自主研发了裂纹显微测量系统,为分凝冰裂纹的原位、无接触式测量提供了便利。试验研究发现:(1)不仅是温度梯度、暖端补水条件,单向冻结冷端降温速率对已冻区分凝冰分布也会产生影响,传统模型(如分凝模型)计算的水分迁移量难以准确反映已冻区冰裂纹分布特征;(2)冻结锋面移动速率对已冻区分凝冰宽度的影响大于温度梯度;(3)冻结过程中已冻区分凝冰宽度随0℃线移动速率呈指数形式变化。最后基于0℃线移动速率提出了已冻区分凝冰宽度预测的经验公式,为工程中评估变降温速率条件下黏土的单向冻胀破坏提供了参考。In the process of unidirectional freezing,the generation and development of segregating ice is an important factor affecting the structural characteristics of frozen and thawed soil.Three unidirectional freezing boundary conditions were selected,i.e.,cooling rate(from 0.5 ℃/s to 0.005 ℃/s),cold temperature(from –30 ℃ to –70 ℃),and water replenishment(no water replenishment,constant pressure water replenishment) to explore their influence on the development of segregating ice.To facilitate the measurement of segregating ice,an independent meso-measurement system has been developed using optical microscope digital photography.This system enables in-situ and non-contact measurement of segregating ice cracks.The experimental results demonstrate the following findings:(i) The distribution of segregating ice is not only influenced by temperature gradients and warm end replenishment conditions,but also by the cooling rate at the cold end of the unidirectional freezing process.(ii) The width of the segregating ice in the frozen area is more significantly affected by the movement rate of the frozen front than by the temperature gradient.(iii) During the freezing process,the width of the frozen ice exhibits an exponential relationship with the movement rate of the 0 ℃ line.Based on this characteristic,an empirical formula is proposed to predict the crack width of segregating ice in the frozen zone.This formula can be used as a reference for evaluating unilateral frost heave failure in practical engineering construction,particularly under conditions of varying cooling rates.

关 键 词：单向冻胀 降温速率 黏土 分凝冰裂纹 超低温 

分 类 号：TU445[建筑科学—岩土工程]