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重要影响。因此，土工结构设计所需的土参数必须通过能够模拟地应力条件的室内试验来确定，而Ko固结和平面应变压缩条件是最常见的地应力条件，为研究天然存款地基上长形土结构的强度和变形特性，设计并建造了一种新型的三轴试验箱，在Ko固结和平面应变压缩条件下的粘性土。三轴单元有两对装置，用于保持试样的横向变形为零。这两种装置均用于Ko固结试验，其中一种装置在平面应变试验中采用简单的分离技术，其主要优点是：（1）在三轴室内可以进行粘性土的Ko固结试验，试验时间长，精度高; (2)从Ko固结状态到平面应变压缩状态的转换通过简单的操作技术而顺利进行。(3)在平面应变条件下，试件被均匀压缩至大变形。因此，该装置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.