Muthuchamy Muthukumar

Bio: Muthuchamy Muthukumar is an academic researcher from VIT University. The author has contributed to research in topics: Expansive clay & Pile. The author has an hindex of 1, co-authored 1 publications receiving 9 citations.

Swelling behaviour of expansive clay beds reinforced with encased granular pile anchors

Abstract: Granular pile anchor (GPA) system is a simple and cost-effective foundation technique for resisting the uplift of foundation caused by swelling of expansive clay. This paper presents the heave resu...

Load-Settlement Response of Geotextile Encased Laterally Reinforced Granular Piles in Expansive Soil Under Compression

Abstract: Expansive soils are prone to volumetric changes when interacted with water, which makes them unfavorable in civil engineers’ perspective. Granular piles are the effective and economic ground improvement techniques available under such criteria. As granular piles attain their support from surrounding soil, these generally fail by bulging under compression in soft clays. This limitation can be answered by provision of tubular geotextile encasement around the column. However, when the compressive loads are high, the bulging in granular pile makes the geotextile reach its tensile strength and does not provide any additional improvement. Further, this problem can be solved by providing lateral reinforcement in the column, as it tends to reduce the stress concentration at the top portion of the pile where bulging occurs, improving their performance. The present study deals with the response of granular piles in the presence of encasement and combination of encasement and lateral reinforcement under strain-restricted compression tests. In both floating and end-bearing granular piles, the load capacity of composite soil is substantially increased. The rate of increase in load-carrying capacity was higher when end-bearing granular pile was reinforced with geotextile encasement and minimal with additional lateral reinforcement. The results show that geotextile encased laterally reinforced granular piles of end-bearing type and floating type showed a substantial increase in load-carrying capacity relative to clay by 2.44 and 2.01 times, respectively.

Mechanical-Chemical-Mineralogical Controls on Permeability Evolution of Shale Fractures

Abstract: We report experimental observations of permeation of CO2-rich aqueous fluids of varied acidic potential (pH) on three different shales to investigate mechanical, chemical, and mineralogical effects on fracture permeability evolution. Surface profilometry and SEM-EDS (scanning electron microscopy with energy-dispersive X-ray spectroscopy) methods are employed to quantify the evolution in both roughness on and chemical constituents within the fracture surface. Results indicate that, after 12 hours of fluid flow, fracture effective hydraulic apertures evolve distinctly under different combinations of shale mineralogy, effective stress, and fluid acidity. The evolution of roughness and transformation of chemical elements on the fracture surface are in accordance with the evolution of permeability. The experimental observations imply that (1) CO2-rich aqueous fluids have significant impact on the evolution of fracture permeability and may influence (and increase) shale gas production; (2) shale mineralogy, especially calcite mineral, decides the chemical reaction and permeability increasing when CO2-rich aqueous fluids flow through fractures by free-face dissolution effect; (3) clay mineral swelling reduces fracture aperture and additively calcite pressure solution removes the bridging asperities, which are the main reasons for fracture permeability decrease; (4) competition roles among clay mineral swelling, mineral pressure solution, and free-face dissolution determine how fracture permeability changes. Furthermore, a multiple parameter model is built to analyze effective hydraulic aperture evolution in considering above three mechanisms, which provide a reference to forecast fracture permeability evolution in shale formations.

Load Carrying Capacity of Expansive Clay Beds Reinforced with Geogrid-Encased Granular Pile-Anchors

Abstract: Plate load tests were conducted on unreinforced expansive clay beds and clay beds reinforced with Granular Pile Anchor (GPA) and geogrid-encased GPA to compare their compressive load response. It was found from the tests that the expansive clay beds reinforced with geogrid-encased GPA showed higher load-carrying capacity and improved compressive load response compared with GPA and unreinforced beds. The applied pressure to cause a settlement of 25 mm in the unreinforced clay bed and clay bed reinforced with GPA of length 97 mm and diameter 30 mm (\( \frac{{l_{gp} }}{{d_{gp} }} = 3.23 \)) was respectively 152.78 kPa and 789.4 kPa, showing an improvement of 416.7%. However, the clay bed reinforced with geogrid-encased GPA required a pressure of 858.16 kPa for the same amount of settlement. This shows an improvement of 461.7% with respect to the unreinforced clay bed. Among three types of anchors used in this study, the one with a length of 97 mm and a diameter of 30 mm showed the best load response when tested without geogrid, resulting in an improvement of 659.3% whereas, the same GPA showed a better improvement of 955.57% when encased with geogrid.

Swelling characteristics of andesite foundation induced by water immersion and their influence on ballastless track subgrade

Abstract: To study the mechanical and deformation characteristics of ballastless track subgrade filled with micro-expansion fillers in a water-immersed environment, a physical model of ballastless track subgrade was constructed on a 1:2 scale with expansive andesite fillers. A water immersion test was carried out to model the soaking of the expansive soil foundation caused by rising groundwater. The swelling behaviors of the foundation and their influences upon the mechanics and deformations of the subgrade were analyzed. The lateral swelling pressure of the foundation and the heave of the subgrade obviously increased due to the water immersion, and the values were closely related to the overlying load and lateral restraint. The heave deformation of the double-line ballastless track subgrade showed significant nonuniformity along the lateral direction, causing the track slab to incline with a maximum inclination angle of 1.55×10-3 deg. The heave of the foundation caused a heave in subgrade, but this transferred heave was significantly attenuated. The attenuation rate of the heave at the midline of the track slab was up to 13.38%. The attenuation characteristic can be fully utilized for the anti-heave deformation measures of railway subgrade in expansive soil areas.

Ground improvement using granular pile anchor system: resistance to heave and uplift pressure

Abstract: Expansive soil is found in many parts of the world where its major drawback is its expansion and shrinking property upon moisture absorption and drying during alternation of rainy-dry seasons. Due to its swelling-shrinkage repeated process, fatigue and distress cause crack to structures. Granular pile anchor (GPA) system is a pioneering technique that is utilised in reinforcing these expansive soils. Granular pile anchor (GPA) system is a pioneering technique that is utilised in reinforcing expansive soils. The GPA provides tensile resistance which arrest the exerted upward forces and hence reducing heave. Previous investigations have only focused on load-displacement relationships by utilizing the pull-out technique. In this technique, an external force pulls the GPA and the corresponding displacements are recorded. The results provide indication of the GPA resistance to the applied force. However, in real conditions the heave and expansion forces were developed as a result of the pressure caused by the water absorption which pushes the entire soil bed in the upward direction along with the GPA. Therefore, this paper is aimed to explore this concept by carrying experimental and numerical investigations on a small scale model for a single pile with a diameter of 4 cm, with lengths of 20 and 40 cm. Ultimately, the reinforced soil exhibits reduction in upward force and heave compared to the unreinforced soil. Also, verifications for the testing shows that the relationship between the upward force and heave exhibits almost linear relationship for both experimental and numerical investigations. Therefore, shallow foundations incorporated with a GPA system proves to effectively lessen the heave that occurs in expansive soils which in turn can solve problems for constructions.