The GCTS Electro-pneumatic Cyclic Triaxial Test System is a closed-loop digitally servo controlled apparatus developed for performing static and dynamic triaxial tests. This system is capable of performing isotropic and anisotropic consolidation; UU, CD, and CU triaxial tests with volume change or pore pressure measurements; stress/strain path; Koconsolidation; cyclic loading including cyclic stress path; dynamic shear strength and deformation, Resilient Modulus, liquefaction potential, shear modulus and damping ratio, and other user designed procedures for frequencies at up to 5 Hz with significant amplitudes. The system is also capable of performing flexible-wall permeability tests. The axial loader, cell pressure, and back pressure are servo controlled using any system sensor as feedback. The drain ball valve is also automated. Meets ASTM D3999 and D 5311 specifications.