Baleshwar Singh

Strength and Deformation Behavior of Fiber-Reinforced Cohesive Soil Under Varying Moisture and Compaction States

An experimental study was carried out to investigate the effects of glass fiber reinforcement on the strength and deformation behavior of a cohesive soil under different compaction states by means of unconfined compression tests. The specimens were prepared with varying fiber contents, fiber lengths, dry unit weight and moisture content other than maximum dry unit weight and optimum moisture content of the soil. From the test results, peak strength, failure axial strain, secant modulus and energy absorption capacity of the reinforced soil specimens were calculated and compared with that of the unreinforced soil. The results showed that the relative benefits of fiber reinforcement are highly dependent on the moisture content and dry unit weight of the soil specimens. The peak strength of the reinforced soil specimen increases gradually with increase in dry unit weight, whereas the improvement of peak strength with moisture content occurs up to optimum moisture content. The brittle failure pattern with a single distinct shear plane of the unreinforced soil specimens is gradually transformed to multi-shear failure pattern along with barreling shape at low fiber content, and then to plastic bulging failure with a network of minor fissures at higher fiber content.

Compaction characteristics of lateritic soil mixed with fly ash and lime

Abstract The compaction characteristics of a lateritic soil modified with a low-calcium fly ash and lime was investigated in the laboratory. The maximum amount of soil replaced with fly ash was limited to 50%. Lime was added in quantities varying from 2% to 4% of the dry weight of soil-fly ash mix. Moisture-dry unit weight relationships were determined for the mixes by using a fresh specimen for each point even after a delay period extending up to 3 days. Fresh specimens were also subjected further to three re-compaction cycles without any delay. The test results indicate that the addition of both fly ash and lime cause immediate reduction in the maximum dry unit weight. Compaction delay leads to a further decrease only for mixes containing lime. However, there is an increase in maximum dry unit weight after re-compaction of the soil-fly ash mixes, and the effect is more pronounced for mixes with lime added.

Shear strength response of glass fibre-reinforced sand with varying compacted relative density

Abstract Triaxial compression tests were conducted to investigate the response to loading of glass fibre-reinforced sandy soil of varying relative densities (35, 65 and 85%). The fibre diameter was 0.15 mm, varying in length from 10 to 30 mm, and in content from 0 to 4% by weight of dry soil. The tests were performed at confining pressures ranging from 100 to 400 kPa. The separate and joint effects of fibre content, fibre length and confining pressure on the strength and deformation characteristics of the specimens were evaluated. The strength of specimens increases up to an optimum fibre content value of 3 or 4% depending on length. Fibre reinforcement has restricted the bulging and shear zones for specimens of all relative densities. A non-linear regression model has been developed for predicting the shear strength of reinforced soil, and scaling law has been employed for using the laboratory results for field application.

Investigation of Glass Fiber Reinforcement Effect on the CBR Strength of Cohesive Soil

An experimental study was carried out to investigate the application suitability of randomly distributed glass fiber-reinforced cohesive soil as subgrade material. Glass fiber of 20 mm length with varying fiber contents (fc = 0.25, 0.5, 0.75 and 1% by dry weight of soil) was used as reinforcement. The effects of fiber content variation on compaction parameters of soil, and the effect of fiber content and soaking time variation on CBR strength were investigated. The soaking time was varied from 4 to 40 days. The CBR and secant modulus were calculated at different penetration depths ranging from 2.54 to 12.7 mm. Test results have shown that the glass fiber content has insignificant effect on the OMC and MDD of the soil. The CBR strength is found to increase with penetration depth up to 7.62 mm penetration and thereafter remains almost constant at all fiber contents. The CBR strength and secant modulus of soil have improved significantly with fiber content up to an optimum fiber content value of 0.75%, and decrease with increase in soaking time at any fiber content. The maximum improvement in CBR strength is found out as 2.48, 2, and 1.5 times for 4, 20, and 40 days soaking for 0.75% fiber inclusion. It has been found that the glass fiber-reinforced soil can be extensively used as subgrade material.

Response and capacity of monopod caisson foundation under eccentric lateral loads

ABSTRACT Monopod caisson foundation is a viable alternative for supporting offshore wind turbines located at shallow water depths. This foundation system has to resist overturning moment generated due to resultant lateral load, arising from wind and water wave action, that can act at any loading height above the seabed. This paper presents results of a numerical investigation performed to determine the influence of loading height, caisson geometry and superstructure load on the ultimate lateral capacity, initial stiffness, and soil failure zone of the foundation, when installed in very dense sand. Both the ultimate and serviceable states of the caisson foundation obtained from the analyses are represented in terms of envelopes plotted between lateral load and overturning moment. Simplified expressions, which take into account the influence of caisson geometry, loading height, and soil properties, are also presented to serve as a preliminary base for design of the monopod caisson foundation.