Development and application of multi-field coupled high-pressure triaxial apparatus for soil
Abstract: The increasing severity of ground subsidence, ground fissure and other disasters caused by the excessive exploitation of deep underground resources has highlighted the pressing need for effective management. A significant contributing factor to the challenges faced is the inadequacy of existing soil mechanics experimental instruments in providing effective indicators, creating a bottleneck in comprehensively understanding the mechanisms of land subsidence. It is urgent to develop a multi-field and multi-functional soil mechanics experimental system to address this issue. Based soil mechanics theories, the existing manufacturing capabilities of triaxial apparatus and the practical demands of the test system, a set of multi-field coupled high-pressure triaxial system is developed tailored for testing deep soils (at depths of approximately 3 000 m) and soft rock. This system incorporates specialized design elements such as high-pressure chamber and horizontal deformation testing devices. In addition to the conventional triaxial tester functions, its distinctive feature encompass a horizontal deformation tracking measuring device, a water release testing device and temperature control device for the sample. This ensemble facilitates testing of horizontal and vertical deformation water release and other parameters of samples under a specified stress conditions, at constant or varying temperature ranging from −40°C–90°C. The accuracy of the tested parameters meets the requirements of relevant current specifications. The test system not only provides scientifically robust data for revealing the deformation and failure mechanism of soil subjected to extreme temperature, but also offers critical data support for major engineering projects, deep exploration and mitigation efforts related to soil deformation-induced disaster.
Figure 1. Schematic diagram of main structure with multi-field coupled high-pressure triaxial system
①-1 Loading frame ①-2 Pressure chamber ①-3 Pore water pressure testing device ①-4 Liquid inlet ①-5 Seepage device ② Temperature control device ③ Horizontal deformation testing device ④ Data acquisition and processing device
Table 1. Test accuracy of the developed system
Category Data/mm Distance from the probe to the sample X01 X02, … X060 1st data X11 X12, … X160 1st horizontal deformation data △X11 △X12 … △X160 2nd data X21 X21 … X260 2nd horizontal deformation data △X21 △X22 … △X260 … … … … nth data Xn1 Xn2 … Xn60 Nth horizontal deformation data △Xn1 △Xn2 … △Xn60 Note：(△Xn1= Xn1−X01)
Table 2. Test accuracy of the developed system
Index Vertical pressure Confining pressure Vertical deformation Horizontal deformation Pore water pressure Pore water volume Temperature Unit P/kN б3/MPa S/mm X/mm u/MPa Q/mL °C Range 50 10 30 10 3 100 −40–90 Accuracy 0.01%F.S 0.01%F.S 0.001 ±0.044 0.01% F.S 0. 01 ±0.10 Note Grating displacement gauge Line laser scanning Constant or changing temperature
Table 3. Soil parameters measured under the condition of multi field coupling
Effective stress Vertical deformation The amount of water released Maximum horizontal deformation Volume of water released/volume of deformation Kpa S /mm V /cm3 X /mm % 114 1.864 0.0523 0.982 2.340 203 3.160 0.0918 1.745 2.421 300 5.440 0.1420 3.137 2.175
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