This facility is designed and get it fabricated locally. It mainly consists of model tank, loading arrangement and hopper. Model testing tank of size 2.1m×1.2m×1.2m is made up of 6mm thick steel plates. One side of the tank is transparent and made of acrylic sheets to observe soil movements during testing. A hopper having nine tubes with inverted cones is specially designed for the preparation of soil bed. This is one of the best arrangement for model preparation using popular rainfall method to achieve required density of the sand. The loading arrangement consist of a DC motor, a chain, and a jack driver to apply the fully controlled loading. It provides an easy and simple process to fasten or slow down the rate of loading. A load indicator is attached to load cell in order to measure the magnitude of load. It can be used to test small scale models of different geotechnical structures (e.g shallow and deep foundations etc.,) under static loading conditions.

The laminar box is designed in house, and fabricated locally for better simulation of boundary conditions on the models during earthquakes to study the dynamic behavior of level ground including wave propagation and liquefaction. A laminar box is a flexible container with different layers which allow free movement soil during shaking. It overcomes the limitation of liquefaction table. Layers and membrane inside offer minimum resistance to horizontal shear. Flexible walls and layers of laminar shear box allows simulation actual field conditions unlike rigid tanks. Linear harmonic motion of different displacement and frequencies can be applied using a mechanical shaker. It is fully instrumented with all sensors to capture the complete response of the soil mass. It can be used to study all model geotechnical problems under both free as well as forced vibrations.

The uniaxial Shake table is ideal for performing seismic simulation, liquefaction and vibration tests on models as well as for engineering qualification of components and assemblies for earthquake and vibration resistance. The table is capable of testing a maximum 3 ton payload on the 2.0 m x 1.5 m table with 1g acceleration and a frequency up to 30 Hz. The table is ideally suited to seismic applications because the hydraulic actuator can produce a stroke of +/- 100 mm. It can generate any required wave formation - Sine, Triangular, Square, and Random waveform. This facility can also be utilized for verification of earthquake resistant design of buildings, other structures, devices, etc. The base of the laminar box is a modified such that it can also be placed on a shaking table for enabling application of actual earthquake motions.

Cyclic tri-axial testing apparatus is an electro-hydraulic system, a highly advanced combination of hydraulic and pneumatic technology. This system is suitable to test a sample sizes up to 200mm diameter x 400mm height (sample dia. 50/75/100/200mm) and a cell pressure of 700kPa It can perform both stress and strain controlled testing as per ASTM 3999 & ASTM 5311 for both soils as well as aggregates. It is used to determine the liquefaction resistance, resilient modulus, cyclic strength, complex modulus, and the other dynamic properties (shear modulus and damping ratio) of soils in either undisturbed or reconstituted states by using either load or displacement controlled cyclic loading. In the same apparatus bender element test can also be performed, to determine the initial tangent modulus/small strain shear modulus of soils in the laboratory by propagating a shear wave through the specimen and then measuring its velocity. Small strain shear modulus is then calculated using density of the specimen & the measured shear wave velocity of the material.

Research Scholar - Rajesh Prasad Shukla
Supervisor - Prof. Ravi S. Jakka

The study explored the bearing capacity enhancement of a shallow foundation resting on slopes by providing vertical and inclined skirts, using numerical simulations as well as laboratory model tests under both static and seismic loading. In this study, cohesionless soil bed is prepared using rainfall technique by a hopper from a particular height to achieve a required relative density of soil. Rigid mild steel plates are used as model footings. Model footing is placed at different locations on soil bed and dial gauges are placed on the top the footing at both the ends to measure the settlements. Axial loading is applied on the footing surface using a mechanical motor gauge until failure of the footing. Loading is applied in 15-20 intervals and corresponding settlements are measured from dial gauges. From these load settlements graphs, ultimate loading of strip or skirted footing on level ground as well as sloping ground is determined. It is found from the study that the skirts are very effective for footings resting on slopes. Further, inclined skirts showed greater enhancement of bearing capacity compared to vertical skirts. Provision of the inclined skirt is not only increasing the effective depth of the foundation, but also its effective width. The stiffness of the skirt has a significant influence in the failure mode, and thereby bearing capacity enhancement. Nonlinear multiple regression equations are also developed based on the results of the study, which enable the practicing engineer to obtain the bearing capacity of different skirted footings directly.