宽饱和度范围非饱和粗细混合土的强度演化规律:试验现象  

Unsaturated shear strength characteristics of coarse-fine mixed soils in a wide range of degree of saturation:experimental phenomena

作　　者：赵煜鑫 张禄乾 李旭[1] 赵红芬 ZHAO Yuxin;ZHANG Luqian;LI Xu;ZHAO Hongfen(Key Laboratory of Urban Underground Engineering of Ministry of Education,Beijing Jiaotong University,Beijing 100044,China;The Third Survey and Design Institute of China Railway,Tianjin 300142,China;School of Civil Engineering,Sun Yat-sen University,Zhuhai 519082,China;Southern Marine Science and Engineering Guangdong Laboratory,Zhuhai 510301,China)

机构地区：[1]北京交通大学城市地下工程教育部重点室验室,北京100044 [2]铁道第三勘察设计院集团有限公司,天津300142 [3]中山大学土木工程学院,广东珠海519082 [4]南方海洋科学与工程广东省实验室(珠海),广东珠海510301

出　　处：《岩土工程学报》2023年第11期2278-2288,共11页Chinese Journal of Geotechnical Engineering

基　　金：国家自然科学基金项目(51979002,52279121)。

摘　　要：粗细混合土是自然界和工程中普遍存在的土体类型,其强度对边坡、基坑、挡土墙等岩土工程稳定性至关重要。然而粗细混合土的强度在宽饱和度范围内的演化规律不明,尤其是缺少低饱和度时的试验数据和演化规律。为了阐明粗细混合土强度随饱和度变化的一般规律,采用室内直剪试验研究了7种不同细粒含量的粗细混合土的强度与变形特性。试验结果表明:①在宽饱和度范围内,由于毛细作用和吸附作用对抗剪强度贡献不同,非饱和粗细混合土的抗剪强度随饱和度的变化普遍存在“山峰效应”,即在非饱和残余区内出现了强度极大值,其强度随饱和度或吸力的演化规律可以划分为缓慢增长区、快速上升区和峰后下降区3个阶段。②当饱和度低于残余饱和度时,非饱和土的剪切破坏还出现了典型的脆性破坏特征。③粗细混合土的强度变形特征与细粒含量密切相关,随着细粒含量的增加,土骨架由粗颗粒控制逐渐转变为细粒控制,非饱和强度最大值所对应的细粒含量为50%~80%。The coarse-fine mixed soils are widely distributed in natural and geotechnical engineering practices.Their strength is vital to the stability of geotechnical engineering(e.g.,slopes,foundation pits and retaining walls).However,the unsaturated shear strength characteristics of the coarse-fine mixed soils are not evident in a wide range of degree of saturation(Sr),especially the lack of experimental data in the low range of Sr.In order to clarify the general rules that the unsaturated shear behaviors of the coarse-fine mixed soils in the full range of Sr,a series of direct shear tests are carried out on seven unsaturated coarse-fine mixed soils to study the unsaturated shear strength and deformation characteristics.The test results show that:(1)Based on the contribution of capillary water and adsorbed water to the unsaturated shear strength,the unsaturated shear strength exhibits a"peak behavior",where the shear strength reaches its peak at the residual zone,the shear strength characteristics with Sr or suction can be divided into three stages:slow growth zone,rapid rise zone and post-peak decline zone.(2)Brittle failure occurs when Sr is lower than the residual saturation.(3)The fines content(FC)significantly affects the strength and deformation characteristics of the coarse-fine mixed soils.As FC increases,the soil microstructure changes from a fines-controlled to a coarse-controlled structure.The FC corresponding to the maximum unsaturated strength is between 50%~80%.

关 键 词：非饱和土 宽饱和度范围 抗剪强度 脆性破坏 

分 类 号：TU443[建筑科学—岩土工程]