基于PIV劈裂试验膨润土抗拉强度公式的修正  

Modification of bentonite tensile strength formula based on PIV splitting test

作　　者：张俊然[1] 翟天雅 Zhang Junran;Zhai Tianya(Henan Province Key Laboratory of Rock and Soil Mechanics and Structural Engineering,North China University of Water Resources and Electric Power,Zhengzhou 450046,China)

机构地区：[1]华北水利水电大学河南省岩土力学与结构工程重点实验室,河南郑州450046

出　　处：《土木工程学报》2023年第4期119-128,共10页China Civil Engineering Journal

基　　金：国家自然科学基金青年基金(41602295);河南省高等学校青年骨干教师培养计划(2020GGJS-094);河南省高等学校重点科研项目(21A410002)。

摘　　要：用于高放废物深地质处置库的压实膨润土砌块因绑扎起吊,会受到拉应力的作用产生拉张裂隙进而影响其使用效果,因此系统研究膨润土的抗拉强度具有重要工程实际意义。基于粒子图像测速技术对压实膨润土进行了一系列的劈裂试验和直接拉伸试验,探求快速且准确获得膨润土抗拉强度的试验方法,同时基于PIV劈裂试验对膨润土抗拉强度公式进行了修正。试验结果表明:压实膨润土的抗拉强度随着含水率的增加呈先增加后减小的趋势,当含水率为13%时其抗拉强度最大。应力-位移关系曲线、位移矢量场和裂隙特征在阶段性划分中存在明显的一一对应关系。当压实膨润土的含水率和初始干密度均相同时,劈裂试验获得的抗拉强度大于直接拉伸强度。采用Frydman提出的修正系数2g和PIV劈裂试验获取的变形参数对劈裂抗拉强度进行修正,修正效果较好。同时在经典巴西劈裂公式基础上引入一个简化修正系数K,结合PIV劈裂试验结果也可快速、准确地获得压实膨润土的直接拉伸强度。Because the compacted bentonite blocks in the deep geological disposal of high-level radioactive waste are bound and hoisted,they may produce tensile cracks when subjected to tensile stress and thus affect the usability.Therefore,the study of the tensile strength of bentonite has important practical significance in engineering practice.Based on the particle image velocimetry(PIV),a series of splitting tests and direct tensile tests were carried out on compacted bentonite to systematically study the tensile strength characteristics of compacted bentonite and the formation process of tensile cracks.Meanwhile,methods to quickly and accurately obtain the tensile strength of compacted bentonite was explored,the formula of bentonite tensile strength was modified based on the PIV spliting test.The test results show that the tensile strength of compacted bentonite increases first and then decreases with the water content,and the tensile strength reaches the maximum value when the water content is 13%.The stress-displacement relation curve,displacement vector field and crack characteristics have obvious one-to-one correspondence in stage division.When the water content and initial dry density of compacted bentonite are the same,the tensile strength obtained by the spliting test is greater than that obtained by the direct tensile test.Frydman's correction coefficient 2g and the deformation parameters of PIV splitting test were used to correct the splitting tensile strength,and the correction effect is good.In addition,a simplified correction coefficient K was introduced based on the classical Brazilian splitting formula,and the direct tensile strength of compacted bentonite could be obtained quickly and accurately by using the PIV spliting test results.

关 键 词：粒子图像测速技术 膨润土 劈裂试验 直接拉伸试验 抗拉强度 裂隙 

分 类 号：TU472.1[建筑科学—结构工程]