一种新型非饱和土温控三轴试验系统的研制与初步应用

为研究温度对非饱和土水力、力学和声学性质的影响,自主研发一套带有弯曲元和精密体变量测的温控式三轴仪。本设备通过在GDS应力路径非饱和土三轴试验系统中增设温控内压力室的方式,实现了对温度变化的精确控制及量测;通过将压差传感器与温控内压力室相结合,实现了温度变化情况下试样体变的精确量测;同时增设了一套弯曲元测试系统,增加了仪器的功能,实现了温度变化情况下对试样实时波速的测试。通过对杭州湾粉细砂土开展4个温度水平的三轴剪切试验以及同一温度水平下的波速测试,结果表明:新仪器能够稳定的控制温度变化条件、精确测量温度变化条件下试样的体变以及测量温度变化条件下试样的实时波速,初步检验了仪器性能的可靠性。该设备整体结构简单,拆装方便,可实现常规非饱和(饱和)土试验与温控非饱和(饱和)土试验之间自由切换,互不干扰。设备研制的成功,将为非饱和(饱和)土的热-水-力-声耦合特性的研究提供方便有效的测试装置。

Development and preliminary application of a new temperature-controlled triaxial test system for unsaturated soils

In order to study the influence of temperature on the hydraulic, mechanical and acoustic properties of unsaturated soils, a temperature-controlled triaxial apparatus with the bender element system (BES) and precision volume change measurement is developed. The instrument can accurately control and measure temperatures by adding a temperature-controlled inner pressure chamber into the stress path unsaturated triaxial testing system of geotechnical digital systems. A differential pressure sensor and the temperature-controlled inner pressure chamber are combined to achieve the precision measurement of volume change of specimens under different temperatures, whilst the BES is equipped to perform the real-time wave velocity tests. A series of experiments are carried out on the sand in Hangzhou Bay, including the triaxial shear tests under four temperature levels and the wave velocity tests under the same temperature level. The results show that the new instrument can control the temperature stably and accurately measure the volume change and the real-time wave velocity of the specimens under different temperatures. The performance of the instrument is satisfactory. Additionally, the instrument has the advantages of simple integral structure, convenient assembly and disassembly, and the function to perform freely the switching tests between the conventional and the temperature-controlled for unsaturated (saturated) soils without mutual interference. The successful development of the instrument will provide a convenient and effective testing device for the study on the hydro-hydraulic-mechanical-acoustic coupling characteristics of unsaturated (saturated) soils.