不同荷载模式作用下双层软黏土地基压缩特性研究  

COMPRESSION CHARACTERISTICS OF DOUBLE-LAYER SOFT CLAY FOUNDATION UNDER DIFFERENT LOADING MODES

作　　者：雷华阳[1,2] 石梁 胡垚 宋英杰 LEI Huayang;SHI Liang;HU Yao;SONG Yingjie(Department of Civil Engineering,Tianjin University,Tianjin 300354,China;Key Laboratory of Coast Civil Structure Safety of the Ministry of Education,Tianjin University,Tianjin 300354,China)

机构地区：[1]天津大学土木工程系,天津300354 [2]天津大学滨海土木工程结构与安全教育部重点实验室,天津300354

出　　处：《工程地质学报》2022年第1期154-163,共10页Journal of Engineering Geology

基　　金：国家重点研发计划项目(资助号:2017YFC0805402);国家自然科学基金(资助号:51578371);土木工程防灾国家重点实验室开放基金(资助号:SLDRCE17-01);天津市自然科学基金(京津冀合作专项项目)(资助号:16JCJDJC40000)。

摘　　要：天津滨海吹填场区典型的"上软下硬"的双层软黏土地基具有复杂的物理性质和工程特性,其在不同荷载作用模式下的变形特性有所不同,在工程实践中往往会产生较大的工后沉降和不均匀沉降,从而导致修建于其上的建筑物出现诸多工程问题。现阶段对于不同荷载作用下吹填场区形成的"上软下硬"双层软黏土地基的变形特性及机理研究甚少,导致理论研究远远落后于工程实践,制约了吹填场区经济建设的快速发展,因此对此类地基的变形特性展开研究显得尤为重要。基于此,本文针对吹填场区"上软下硬"的双层软黏土地基,开展了反复荷载和恒定荷载作用下的一维固结试验和扫描电镜试验(SEM),得到了不同荷载模式作用下的压缩特性及其微观机理,为吹填场区双层软黏土地基变形模型建立及长期工后沉降预测提供理论依据。研究表明:双层软黏土地基的压缩系数和固结系数在反复荷载作用初期明显减小,而后缓慢减小直至趋于稳定;与反复荷载相比,恒定荷载作用下试样的压缩系数初期值增加,固结系数初期值减小,其变化量均在40%~50%的范围内;当荷载等级一定时,反复荷载作用引起双层软黏土地基产生的沉降量相比于恒定荷载作用多30%~45%;随着荷载等级的增加,土样内部大孔隙受到挤压而减少,孔隙的圆度和定向性加强,土体结构更密实,均一化程度提高;相比于恒定荷载模式,反复荷载作用下土样内部孔隙形状更接近于圆形,孔隙定向性更好,土体内部结构强化程度大,但有序性相对较差。The upper soft and lower hard double-layer soft clay foundation in reclamation land of costal area in Tianjin has complicated physical properties and engineering characteristics. Its deformation characteristics are different under different loading modes. This phenomenon can result in large post-construction settlement and uneven settlement in engineering practice. It can further lead to many engineering problems such as economic losses and even casualties. At present, most of the recent studies focus on the upper hard and lower soft double-layer soft clay foundation under constant loading mode. However, non-negligible settlement can happen due to some foundation under repeated loading. So far, the consolidation deformation mechanism of the double-layer soft clay foundation under different loading modes is deficient. The theoretical research lags far behind the engineering practice, which restricts the development of economic construction in relevant area. Therefore, it is particularly significant to study the deformation characteristics of double-layer soft clay foundation. This paper conducts one-dimensional consolidation test and Scanning Electron Microscope(SEM)test on the double-layer soft clay foundation in reclamation land, and then obtained compression characteristics and microcosmic mechanism of the soil sample. Applying one-dimensional consolidation test, this paper studies the deformation differences of double-layer soft clay foundation under repeated loading mode and constant loading mode. Furthermore, it discusses the micro-deformation mechanism of double-layer soft clay foundation under different loading modes based on the SEM test. The experimental results provide theoretical basis to establish deformation model and predict long-term settlement of the double-layer soft clay foundation. The results show the follows:(1)Under repeated loading mode, the compression coefficient and consolidation coefficient of double-layer soft clay foundation decrease obviously at the initial stage and then slowly decr

关 键 词：软黏土 双层地基 荷载模式 压缩特性 微观机理 

分 类 号：TU411.5[建筑科学—岩土工程]