Design and construction of a new triaxial apparatus for Ko-consolidation and plane strain compression tests of cohesive soils

加载过程中的应力历史和应力路径对粘性土的强度和变形特性有很大影响。因此，土结构设计中的土体参数必须通过室内试验来确定，这些参数必须能够接近地应力条件。Ko固结和平面应变压缩条件是最常见的地应力条件，例如在天然堆积地基上建造长土体结构时。为了研究粘性土在Ko固结和平面应变压缩条件下的强度和变形特性，设计并建造了新型三轴室。三轴室有两对装置，用于将试件的横向变形保持在零。这两种装置都用于Ko固结试验，其中一种是通过简单的平面应变试验技术从试件上分离出来的。该装置的主要优点是：(1)粘性土的Ko固结可以在三轴单元中进行长时间的固结，精度令人满意。(2)从Ko固结状态到平面应变压缩状态的转换，以简单的操作技术顺利进行。(3)在平面应变条件下，试件被均匀压缩至大变形。因此，该仪器适用于破坏时变形较大的粘性土。

Strength and deformation properties of cohesive soils are influenced significantly by the stress history and stress path during loading process. Soil parameters for design of earth structures, therefore, must be determined from the laboratory tests which are able to simulate the in-situ stress conditions closely.The conditions of Ko-consolidation and plane strain compression are most frequent in-situ stress conditions, such as in construction of long soil structures on natural deposit grounds.The new type of triaxial cell was designed and constructed to study strength and deformation properties of cohesive soils under the conditions of Ko-consolidation and plane strain compression. The triaxial cell has two pairs of devices for maintaining the lateral deformation of specimen at zero. Both of the devices are used in Ko-consolidation test, and one of them is detached from the specimen by means of simple technique in plane strain test.Main advantages of the apparatus are as follows; (1) Ko-consolidation of cohesive soils can be performed over a long time with satisfactory accuracy in the triaxial cell. (2) A change from the state of Ko-consolidation to the plane strain compression condition is conducted smoothly by means of simple operational technique. (3) The specimen is compressed uniformly to large amount of deformation under plane strain condition. Thus, the apparatus is applicable to cohesive soils with large deformation at failure.