一种三维土压力盒的工作原理及其应用

Principle and its application of a three-dimensional earth pressure cell

基于应力理论,设计了一种能测量土中三维应力状态的三维土压力盒,由一个开槽的十二面体基座和6个常规土压力盒组成。根据任一方向上正应力与常规应力表示方法 6个分量之间的关系,建立了三维土压力盒测试数据与常规应力表示方法之间的转换矩阵,给出了由测试数据到常规应力状态的计算方法,并进行了误差分析。考虑基座加工便利性和测试过程的便利性要求,着重阐述了等菱形十二面体三维土压力盒的工作原理、制作过程、测试方法和数据处理等关键环节。对某不饱和重塑土进行了一维压缩,并用测试装置测量了土中6个方向的正应力,推演出了对应的常规应力表达值。结果表明,常规应力表示方法中的两个水平应力基本相等且小于竖向应力,同时水平面和两个竖直面上的剪应力很小,与一维压缩的力学特点吻合,测试装置的设计合理。

Based on the stress theory, a three-dimensional earth pressure cell was designed for measuring three-dimensional stress state in soil. The device is composed of a slotted dodecahedron base and six conventional earth pressure cells. According to relationship between any normal stress in a direction and the six components of general three-dimensional stress, a transformation matrix was established from test data obtained by three-dimensional earth pressure cell to general stress state. The calculation method of the test data to the general stress state was given; and the error analysis was carried out. Considering machining convenience of the base and simplicity of the test procedure, the paper focuses on illustrating the principle, production process, test method and data processing for the rhombic dodecahedron three-dimensional earth pressure cell. One-dimensional compression experiment on an unsaturated remolded soil was performed and a device measuring normal stress in six directions was given herein. The conventional stress results deduced by test data show that the two horizontal stress is substantially equal and less than the vertical stress. At the same time, the three shear stresses of the conventional stress are small and near zero. That is consistent with mechanical characteristics of one-dimensional compression on soil. Therefore, the design of the device is reasonable. © 2016, Science Press. All right reserved.