Wellbore and tunnel problems are of true triaxial stress state, even if the ground is under axisy... more Wellbore and tunnel problems are of true triaxial stress state, even if the ground is under axisymmetric loading condition. A closed-form analytical solution is proposed using Drucker–Prager failure criterion. The solutions are obtained for rock mass exhibiting elastic–perfectly plastic or elastic–brittle–plastic behaviour. The proposed solution is then compared with the finite element analysis (FE-analysis) results. Parametric studies are also carried out. The results of the proposed analytical solution are found to be in good agreement with the FE-analysis results. The proposed analytical solution can thus be used for predicting the stresses and deformation of underground circular openings considering true triaxial stress state.
Dynamic experiments were conducted on model single piles of 25 mm diameter having different lengt... more Dynamic experiments were conducted on model single piles of 25 mm diameter having different length-to-diameter ratios and embedded in a simulated elastic half space filled with clay soil. Pile response was observed and measured using a Data Acquisition System. Pile response to dynamic lateral loads was also predicted by a simple 2D soil-pile interaction finite element model using the software, PLAXIS. The observed and predicted pile response to dynamic lateral load was compared and it was found that the simple 2D-model reasonably predicts the natural frequency of the soil-pile system; it highly overestimates the peak displacement amplitude. The model predicts the depth of occurrence of maximum bending moment with reasonably good accuracy for all piles in medium stiff clay.
Soil reinforcement using natural fibers has been successfully employed in different projects. Amo... more Soil reinforcement using natural fibers has been successfully employed in different projects. Among the natural fibers, the use of waste human hair fibers as a reinforcing material can be the solution for sustainable development. This study presents characterization of human hair fiber–reinforced sand using direct shear tests under dry and saturated conditions. Tests were conducted in three series: (i) Test Series-1: using unsorted human hair fibers (as collected from barber shops) under dry conditions, (ii) Test Series-2: using unsorted human hair fibers under saturated conditions, and (iii) Test Series-3: sorted fibers with lengths of 10, 15, and 20 mm to examine the effect of fiber length when under saturated conditions of sand. All test specimens were prepared at 80 % relative density. Initially, experiments were carried out on dry sand with fiber reinforcement up to 2.0 % by weight of sand. Under saturated conditions, the percentage of fiber content was restricted up to 1.0 %, as formation of fiber clusters was noticed beyond 1.0 %. Under saturated conditions, specimens were prepared with initial moisture content ranging from 1.0–3.0 % by weight of soil for easy homogeneous mixing and then saturated. It is found that the reinforcement using human hair fibers significantly affects the shear behavior of dry sand. However, under saturated conditions, the human hair fiber reinforcement is able to sustain shear strength parameters similar to unreinforced sand, even though these parameters are likely to reduce. The use of unsorted fibers as reinforcement is more beneficial than that the use of the sorted fibers of uniform length.
Wellbore and tunnel problems are of true triaxial stress state, even if the ground is under axisy... more Wellbore and tunnel problems are of true triaxial stress state, even if the ground is under axisymmetric loading condition. A closed-form analytical solution is proposed using Drucker–Prager failure criterion. The solutions are obtained for rock mass exhibiting elastic–perfectly plastic or elastic–brittle–plastic behaviour. The proposed solution is then compared with the finite element analysis (FE-analysis) results. Parametric studies are also carried out. The results of the proposed analytical solution are found to be in good agreement with the FE-analysis results. The proposed analytical solution can thus be used for predicting the stresses and deformation of underground circular openings considering true triaxial stress state.
Dynamic experiments were conducted on model single piles of 25 mm diameter having different lengt... more Dynamic experiments were conducted on model single piles of 25 mm diameter having different length-to-diameter ratios and embedded in a simulated elastic half space filled with clay soil. Pile response was observed and measured using a Data Acquisition System. Pile response to dynamic lateral loads was also predicted by a simple 2D soil-pile interaction finite element model using the software, PLAXIS. The observed and predicted pile response to dynamic lateral load was compared and it was found that the simple 2D-model reasonably predicts the natural frequency of the soil-pile system; it highly overestimates the peak displacement amplitude. The model predicts the depth of occurrence of maximum bending moment with reasonably good accuracy for all piles in medium stiff clay.
Soil reinforcement using natural fibers has been successfully employed in different projects. Amo... more Soil reinforcement using natural fibers has been successfully employed in different projects. Among the natural fibers, the use of waste human hair fibers as a reinforcing material can be the solution for sustainable development. This study presents characterization of human hair fiber–reinforced sand using direct shear tests under dry and saturated conditions. Tests were conducted in three series: (i) Test Series-1: using unsorted human hair fibers (as collected from barber shops) under dry conditions, (ii) Test Series-2: using unsorted human hair fibers under saturated conditions, and (iii) Test Series-3: sorted fibers with lengths of 10, 15, and 20 mm to examine the effect of fiber length when under saturated conditions of sand. All test specimens were prepared at 80 % relative density. Initially, experiments were carried out on dry sand with fiber reinforcement up to 2.0 % by weight of sand. Under saturated conditions, the percentage of fiber content was restricted up to 1.0 %, as formation of fiber clusters was noticed beyond 1.0 %. Under saturated conditions, specimens were prepared with initial moisture content ranging from 1.0–3.0 % by weight of soil for easy homogeneous mixing and then saturated. It is found that the reinforcement using human hair fibers significantly affects the shear behavior of dry sand. However, under saturated conditions, the human hair fiber reinforcement is able to sustain shear strength parameters similar to unreinforced sand, even though these parameters are likely to reduce. The use of unsorted fibers as reinforcement is more beneficial than that the use of the sorted fibers of uniform length.
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Papers by Ramanathan Ayothiraman