A NEW MULTI-FUNCTIONAL TRUE TRIAXIAL FLUID-SOLID COUPLING EXPERIMENT SYSTEM AND ITS APPLICATIONS
YIN Guangzhi1，2，3，LI Minghui1，2，3，XU Jiang1，2，3，WANG Weizhong1，2，3，LI Wenpu1，2，3，
LI Xing1，2，3，SONG Zhenlong1，2，3，DENG Bozhi1，2，3
(1. State Key Laboratory of Coal Mine Disaster Dynamics and Control，Chongqing University，Chongqing 400030，China；2. College of Resources and Environmental Sciences，Chongqing University，Chongqing 400030，China；3. State and Local Joint Engineering Laboratory of Methane Drainage in Complex Coal Gas Seam，Chongqing University，Chongqing 400030，China)
Abstract：A new multi-functional true triaxial fluid-solid coupling experiment system was designed，fabricated， calibrated，and successfully tested to better simulate in-situ triaxial stress conditions and reveal geomechanical properties and seepage laws for rocks and coals subjected to these conditions. The experiment system comprises a load frame，a true triaxial pressure vessel，a high pressure loading system，an internally sealed seepage system，a control and data acquisition system and an acoustic emission monitoring system. The advantages and innovations of the experiment system include：(1) Geomechanical and seepage experiments can be performed for different stress-strain paths under uniaxial，biaxial or true triaxial stress conditions. (2) Three new stress and strain control modes(Trace-F，Trace-D and Trace-Df) are implemented to ensure that the center point of the specimen stays in the same position during experiments. (3) The internally sealed seepage system is designed to accomplish the independent control and monitoring of fluid flow in the specimen under true triaxial stress conditions. (4) To reduce the specimen end friction effect，stiff loading mode is applied in two directions and either flexible or stiff loading mode is applied in the third direction. In addition，high frequency dynamic control is implemented for the load system，therefore experiments with complex stress-strain paths can be performed. (5) New multi-functional loading platens are designed to accommodate hydraulic fracturing experiments. (6) The experiment system can apply a force of up to 6 000 kN in each of two directions and 4 000 kN in the remaining direction. The applied fluid pressure can be up to 60 MPa based on a servo-controlled supercharger. A series of testing methods and experiments were performed to verify the accuracy and reliability of the experiment system. This system will provide a comprehensive new tool to study geomechanical properties and seepage laws for rock and coal under true triaxial stress conditions，which can be further applied to research in areas such as geological storage of CO2，efficient oil-gas exploitation and deep underground rock engineering applications.
2015, Vol. 34 
