新型非饱和土三轴压缩试验仪的研制

发布时间：2018-02-03 02:53

本文关键词： 非饱和土三轴压缩试验仪器研制数字图像测量水压力控制器　出处：《大连理工大学》2014年硕士论文　论文类型：学位论文

【摘要】：地球表层土有很大一部分处于地下水位以上,因此工程应用中所遇到的土有很多为非饱和土,所以对非饱和土力学性质的研究尤为重要。研究土壤力学性质最重要的试验为三轴压缩试验,即对土样在轴对称条件下施加应力,通过测量其应力应变关系得到其力学性质。饱和土三轴压缩试验仪发展比较成熟,应用广泛,但是非饱和土三轴压缩试验仪由于非饱和土理论体系不完善以及试验测试技术较复杂等原因,目前仍没有较为完善的仪器。国内外现有非饱和土三轴压缩试验仪存在很多可以改进之处,例如：应变测量均采用传统的接触式测量,对试样扰动较大,而且非饱和土试验中试样的体积变化无法精确测量；孔隙气压加载系统提供较高压力时供气量不足,需要先借助外部气源提高初始压力；由下至上的轴向应力加载导致压力室的随动,容易对压力室以及与其相连的管路内的压力的稳定性造成影响；压力室充水需要借助额外的储水容器；仪器结构不紧凑等。结合本论文自主研发的非饱和土三轴压缩试验仪,基本上成功地解决了上述问题,并且在很大程度上提高了非饱和土三轴压缩试验的测量精度。该仪器主要特点有：应变测量采用了具有自主知识产权的土样全表面变形数字图像测量系统,该系统能够对土样的标定点在整个实验过程中的空间位置变化进行实时采集记录,然后通过后处理程序对采集的信息进行运算,得到试样各种参数的变化；轴向应力加载采用由上至下的加载方式,并内置水下测力传感器,并且在满足常规的静力加载的前提下增加了力反馈加载方式和位移反馈加载方式以及基于上述两种加载方式的循环加卸载；试样基质吸力由电气比例阀以及水压力控制器进行实时控制,响应快、精度高、压力稳定；对应力加载系统、围压加载系统、吸力控制系统等进行了优化设计,达到了布局合理、结构优化、操作简便、一机多用等效果。本文作者在综合分析非饱和土三轴压缩试验的流程以及仪器应具备的功能的基础上,完成了以下工作：仪器各向应力加载系统的设计和整机布局；试样基质吸力控制方案的设计实施；仪器控制流程设计、原件选型以及电控板的连接；全表面数字图像测量系统的引入；仪器安装、调试与试验。
[Abstract]:A large part of the earth's surface soil is above the groundwater level, so many of the soils encountered in engineering applications are unsaturated soils. Therefore, it is particularly important to study the mechanical properties of unsaturated soils. The most important test to study soil mechanical properties is triaxial compression test, that is, applying stress to soil samples under axisymmetric conditions. The mechanical properties are obtained by measuring the stress-strain relationship. The saturated soil triaxial compression tester is developed and widely used. However, due to the imperfect theoretical system of unsaturated soil and the complexity of testing technology, there is still no perfect instrument for unsaturated soil triaxial compression test instrument. At home and abroad, there are many improvements in the existing unsaturated soil triaxial compression test instruments. For example, the strain measurement adopts the traditional contact measurement, which has a great disturbance to the sample. Moreover, the volume change of the sample can not be accurately measured in unsaturated soil test. When the pore pressure loading system provides the higher pressure, the gas supply is insufficient, so it is necessary to increase the initial pressure with the help of the external gas source. The axial stress loading from the bottom to the top leads to the follow-up of the pressure chamber, which can easily affect the stability of the pressure chamber and the pressure in the pipe connected to it. The pressure chamber needs to be filled with additional water storage vessels; The structure of the instrument is not compact, etc. Combined with the unsaturated soil triaxial compression tester developed in this paper, the above problems have been solved successfully. The measurement accuracy of unsaturated soil triaxial compression test is improved to a great extent. The main features of this instrument are as follows: the full surface deformation digital image measurement system with independent intellectual property rights is used for strain measurement. The system can collect and record the change of the space position of the standard spot of the soil sample in the whole experiment process in real time, then calculate the collected information through the post-processing program, and get the change of the sample's various parameters. Axial stress loading adopts top-down loading mode, and the underwater force sensor is built in. The loading mode of force feedback and displacement feedback and cyclic loading and unloading based on the above two loading modes are added under the premise of satisfying the conventional static loading. The suction of the sample matrix is controlled by electric proportional valve and water pressure controller in real time, which has the advantages of fast response, high precision and stable pressure. The stress loading system, the confining pressure loading system and the suction control system are optimized, and the results are as follows: reasonable layout, optimized structure, simple operation and multipurpose. On the basis of synthetically analyzing the flow chart of unsaturated soil triaxial compression test and the functions of the instrument, the author has accomplished the following work: the design of the stress loading system in each direction of the instrument and the layout of the whole machine; The design and implementation of the control scheme of sample matrix suction; Design of instrument control flow, selection of original parts and connection of electronic control board; The introduction of full surface digital image measurement system; Instrument installation, commissioning and testing.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU415

【参考文献】