Standard test methods for determining one-dimensional consolidation properties of soils using incremental loading in accordance with ASTM D2435, or AASHTO 216, and of those of other international and organizations, do not accurately predict the values of vertical settlement, coefficients of consolidation in horizontal and vertical directions, and modulus of elasticity in vertical direction, because fixed ring used in these tests do not allow horizontal settlement and dissipation of excess pore-water pressures in horizontal direction, whereas, in field, under application of a vertical load, both horizontal and vertical settlements occur along with dissipation of excess pore-water pressures in both vertical and horizontal directions. To overcome this more than 100 year old problem, the inventor (Dr. Ramesh Chandra Gupta, Ph. D., P.E.) has invented a test device for determining three-dimensional consolidation properties of soils, using a flexible ring which permits development of horizontal and vertical displacements, and dissipation of excess pore-water pressures in both horizontal and vertical directions, along with increased lateral resistance as takes place in field at any depth in a soil deposit when vertical load at the surface is applied.
The flexible ring consists of filter fabric around the soil specimen, rubber membrane around the filter fabric, circular segmental metal plates around the membrane and elastomeric rubber bands or spring loaded jacket around the segmental plates, and allows horizontal and vertical displacements, dissipation of pore-water pressures in horizontal and vertical directions to take place with increased lateral resistance with each increment of vertical load like those in the field. Thus new test device simulates field condition to allow accurate determination of three-dimensional consolidation properties of soils (such as settlements, coefficients of consolidation in horizontal and vertical directions, and modulus of elasticity).
For this new test device, conventional incremental consolidation frame or triaxial type chamber system either with the triaxial loading system or modified to adapt to incremental consolidation frame, shall be used to perform three-dimensional consolidation tests.