A Large-Scale True Triaxial Seepage Apparatus for Evaluating Impact under High Stress State and High Hydraulic Heads

Seepage phenomenon can be characterized as a hydromechanical coupled issue that threatens the performance of hydraulic facilities as well as infrastructures. In this study, a large-scale true triaxial seepage apparatus was developed to investigate the hydraulic parameters of coarse-grained cohesionless soil under complex stress states and various water heads. A specimen with a maximal size of 1,050 by 550 by 550 mm was provided, and a 3-D loading system was equipped. The loading capacity in all 3 directions reaches 9 MPa, and the water supply system can produce a water head equivalent to 300 m. A detailed description of each component of the true triaxial seepage apparatus is presented. A series of tests were carried out using coarse-grained cohesionless soil naturally sampled from BaTang Dam in Sichuan Province, China. The experimental arrangement encompassed the repeatability tests and various horizontal seepage tests under different triaxial stress states. Test results show that the hydraulic conductivity of the test soil exhibits a negative power relationship with the hydraulic gradient. The newly developed apparatus is verified to be a useful tool to investigate the hydraulic features of coarse-grained cohesionless soil under triaxial stress conditions.