基于核磁共振的红黏土抗剪强度与孔隙关系研究  

Study on relationship between shear strength and pore structure of lateritic clay based on NMR

作　　者：卫国芳[1] WEI Guofang(Sanmenxia Polytechnic,Sanmenxia 472000,China)

机构地区：[1]三门峡职业技术学院,河南三门峡472000

出　　处：《人民长江》2021年第11期155-160,共6页Yangtze River

基　　金：国家自然科学基金项目(41262011)。

摘　　要：为探究多次干湿循环作用对红黏土孔隙结构的影响,揭示孔隙结构与抗剪强度的内在联系,基于核磁共振技术,测定试样经历0~8次干湿循环后的T_(2)曲线,并测定试样的抗剪强度,以分析不同尺寸的孔隙与抗剪强度的关系。结果表明:①第4次循环后,试样黏聚力衰减约54.9%;在第4~8次循环过程中黏聚力趋于稳定。②随着循环次数增加,内摩擦角在一定范围内波动,未见明显规律。③根据不同循环次数的T_(2)曲线,土体孔隙可分为团粒孔(T_(2)<1.52 ms)、粒间孔(1.52 ms≤T_(2)<31.64 ms)、裂隙(T_(2)≥31.64 ms),不同尺寸的孔隙对土体抗剪强度的影响不同。④团粒孔在干湿循环作用下几乎保持不变,粒间孔和裂隙随着循环次数的增大而近似呈对数增加。⑤粒间孔和裂隙都与黏聚力呈良好的线性负相关,它们是导致黏聚力衰减的主要因素。根据分析结果,提出了基于综合权重分析的孔隙指数I,该指数能综合体现不同尺寸孔隙(粒间孔和裂隙)对黏聚力的影响;I与黏聚力相关性良好,可用于多次干湿循环影响下土体强度的评价。To explore the impact of multiple dry-wet cycles on the pore structure of lateritic clay and to reveal the internal relationship between pore structure and shear strength,we tested the T_(2) curve and shear strength of specimen that experienced 0~8 cycles,and analyzed the relationship between pore size and shear strength.The results showed that after the 4th cycle,cohesion of the specimen decreased about 54.9%,while it tended to be stable in following cycles.As the cycle number increased,the friction angle fluctuated irregularly within a certain range.Based on T_(2) curves under different cycles,pore of soil was divided into three types:aggregate pore(where T_(2)<1.52 ms),intergranular pore(1.52ms<T_(2)<31.64 ms),and fissure(T_(2)>31.64 ms).The influence of pore sizes on the shear strength of soil was different.The aggregate pore almost remained unchanged after 0~8 cycles,and the intergranular pore and fissure increased logarithmically with the increase of cycle number.As the main factor leading to the attenuation of cohesion,the intergranular pores and fissures showed a good linear negative correlation with cohesion.A pore index based on comprehensive weight analysis was proposed,which comprehensively reflected the influence of intergranular pore and fissure on cohesion.The proposed index showed a good correlation with cohesion,which can be used to evaluate the influence of dry-wet cycles on soil strength.

关 键 词：干湿循环 孔隙结构 核磁共振 抗剪强度 

分 类 号：TU443[建筑科学—岩土工程]