Conference Papers
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Item Stabilization of lateritic soil using bio-enzyme(2008) Mithanthaya, I.R.; Ravishankar, A.U.Soil stabilization is a technique aimed at increasing or maintaining the stability of a soil mass, or otherwise improving its engineering properties. Various techniques are being used for stabilization of soil. Sub-base is an integral part of the road pavement structure. The main function of the sub-base is to provide a stress transmitting medium for spreading the surface wheel load in such a manner as to prevent shear and consolidated deformations. A number of researchers worked on characterizing variousus properties of the laterite soil and found that the following problems could be associated with the laterite: 1)In the majority of cases, the laterite doesn't satisfy conventional specifications for road construction materials especially road base. 2) The laterit undergoes property changes during construction; gradation being considered to be the most sensitive. To improve on the above deficiencies and consequently to improve on there field performance characteristics, laterites need to be stabilized. Bioenzyme - stabilization is a newer technique for strengthening the sub-base soil. The Bioenzyme alters the engineering properties of soil such as the capacity to bear loads. These enzymes are liquid additives, which act on the soil to reduce the voids between soil particles and minimize absorbed water in the soil for maximum compaction. The locally available laterite soil procured from the field is used to improve the strength and bearing capacity. One type of Bio-enzyme namely TerraZyme has been used for stabilization of laterite soil. In this study soil with variable enzyme dosages were tested for stabilization process and strength of the stabilized soil has been evaluated after curing period of one week, two weeks, three weeks and four weeks. The tests were carried out to determine the consistency limits, CBR, unconfined compressive strength and permeability of the soil specimens with and without enzyme for a curing period of one week to four weeks. The effect of enzyme on different percentages of sand blended laterite soil was also studied for the curing periods. The enzyme treated soil showed significant improvement in CBR (California bearing ratio) and UCS (Unconfined Compressive strength) with curing. © AES-Advanced Engineering Solutions.Item Fatigue behavior of Lateritic soil stabilized with enzyme and effectiveness of flexible pavement with stabilized soil as sub-base(2011) Mithanthaya, I.R.; Ravishankar, A.U.; Rao, N.B.The Lateritic soil is abundantly available in coastal Karnataka (India). To improve its properties the soil has to be stabilized either mechanically or chemically. Soil stabilization using enzyme is one of the methods developed recently. Various experimental investigations have shown that Atterberg's limit values are improved favorably and there is increase in CBR values. The unconfined compressive strength increases with the increase in curing period when treated with enzyme. These improvements mainly depend on type of soil and enzyme used. In recent past many enzymes have come to the market which can be used as a stabilizing agent. In the present investigation commercially available enzyme is used for stabilization of lateritic soil and improvement in Unconfined Compressive Strength (UCS) has been investigated. It has been observed that the enzyme treated soil shows significant improvement in terms of UCS with longer curing period. Considering this, fatigue behavior of enzyme stabilized soil samples has been studied to find relationship between UCS, fatigue life, enzyme dosage and curing period and correlation between them has been established through multiple regression analysis. Considerable amount of improvement is observed in its fatigue behavior when subjected to repeated loading. This enzyme stabilized soil is used soil as sub base layer in the design of flexible pavements. Using the results of laboratory tests on enzyme treated lateritic soil, the thickness of sub base required has been calculated with the help of "KENPAVE" software. The thickness obtained is compared with the thickness suggested by Indian Road Congress (IRC) for defined sub grade strength (CBR value). Cost comparison has been made considering conventional method of design. © 2011, Advanced Engineering Solutions.Item Estimation of Willingness to Pay for Reducing Road Accident Risk Using Route Choice Model(Springer Science and Business Media Deutschland GmbH, 2023) Sumayya Naznin, P.H.; Anandu, V.G.; Panackel, L.S.; Ravishankar, A.U.The proportionality of road accidents with urbanization triggers road accident cost analysis, as a prime component in the planning and designing of road projects. However, proper quantification of accidents and analyzing every parameter associated with it is a tedious task and requires expert approaches. This study deals with the cost of road accidents in Thiruvananthapuram city as it houses the most critical accident spots in the state of Kerala. Essential stretches of roads to be analyzed were identified using Accident Severity Index (ASI). A Stated Preference (SP) survey was conducted to estimate the trip-wise mean willingness to pay value (WTP) of road users of the selected road stretches based on logit models. Travel time, travel costs, and accident rates were taken as the attributes. The behavior of individual users was interpreted from the coefficients estimated from the models. The mode-specific variables showed relations consistent with the expectations. The willingness to pay value to avoid a critical accident estimated from the final model was found higher for short trip setting (Rs.1.08/trip), which indicates the importance of safety of the short frequent trips among the road users compared to the longer trip setting (Rs. 0.72/trip). © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.Item Unmodified Bitumen in SMA: A Sustainable and Cost-Effective Approach(Springer Science and Business Media Deutschland GmbH, 2025) Arun, U.; Chinnabhandar, R.K.; Talkeri, H.T.; Yatish, R.G.; Ravishankar, A.U.Stone Matrix Asphalt (SMA) is a Hot Mix Asphalt (HMA) mixture consisting of a discontinuous aggregate gradation characterised by a high coarse aggregate content (between 70 and 80%), a high percentage of binder (typically between 6 and 7%) and a filler content as high as about 10%. SMA has an aggregate skeleton which imparts high strength and rutting resistance to the mixture. The high binder content though provides the mixture with durability, it also drains through the void spaces in the aggregate skeleton during production, transportation and placement of the mixture in the field. Hence, to reduce the drainage of bitumen and bitumen mortar, the SMA guidelines suggest using a modified bitumen or pelletised cellulose fibres in the mixture when a conventional bitumen such as Viscosity Graded (VG 30) is used. However, the production of cellulose fibres is not only expensive but also requires trees to be cut since cellulose is obtained from plant sources leading to deforestation. Due to the high cost of Polymer Modified Bitumen (PMB), the SMA mixtures prepared with the modified bitumen are also expensive. Hence, the present study focuses on the laboratory evaluation of SMA mixes using a conventional Viscosity Graded bitumen (VG 40) without the use of pelletised cellulose fibres. The results indicated that the susceptibility of mixtures to drainage of binder and/or binder mortar was within the permissible limit of 0.3% by weight of the mixture. The mechanical and moisture susceptibility tests conducted on compacted specimens indicated that the performance is comparable to that of the mixtures prepared using PMB. Further, it was noted that only the grades of bitumen softer than VG 40 required cellulose fibres to reduce drain-down. The study also revealed a reduction in cost due to not using cellulose fibres with VG 40 bitumen or modified bitumen, which makes it more environmentally friendly and sustainable. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.