Volume Change behaviour in Calcitic Soil influenced with Sulphuric Acid using Artificial Neural Networks

This paper elucidates the methodology of applying artificial neural network model (ANNM) to predict the percent swell of calcitic soil in sulphuric acid solutions, a complex phenomenon involving many parameters. Swell data required for modelling is experimentally obtained using conventional oedometer tests under nominal surcharge. The phases in ANN include optimal design of architecture, operation and training of architecture. The designed optimal neural model (3-5-1) is a fully connected three layer feed forward network with symmetric sigmoid activation function and trained by the back propagation algorithm to minimize a quadratic error criterion.The used model requires parameters such as duration of interaction, calcite mineral content and acid concentration for prediction of swell. The observed strong correlation coefficient (R2 = 0.9979) between the values determined by the experiment and predicted using the developed model demonstrates that the network can provide answers to complex problems in geotechnical engineering.

Design of Geocell Reinforcement for Supporting Embankments on Soft Ground

The methods of design available for geocell-supported embankments are very few. Two of the earlier methods are considered in this paper and a third method is proposed and compared with them. The first method is the slip line method proposed by earlier researchers. The second method is based on slope stability analysis proposed by this author earlier and the new method proposed is based on the finite element analyses. In the first method, plastic bearing failure of the soil was assumed and the additional resistance due to geocell layer is calculated using a non-symmetric slip line field in the soft foundation soil. In the second method, generalpurpose slope stability program was used to design the geocell mattress of required strength for embankment using a composite model to represent the shear strength of geocell layer. In the third method proposed in this paper, geocell reinforcement is designed based on the plane strain finite element analysis of embankments. The geocell layer is modelled as an equivalent composite layer with modified strength and stiffness values. The strength and dimensions of geocell layer is estimated for the required bearing capacity or permissible deformations. These three design methods are compared through a design example.

Modeling wrap faced reinforced soil retaining walls subjected to dynamic excitation

This paper describes some of the physical and numerical model tests of reinforced soil retaining walls subjected to dynamic excitation through uni-axial shaking tests. Models of retaining walls are constructed in a perspex box with geotextile reinforcement using the wrap around technique with dry sand backfill and instrumented with displacement sensors, accelerometers and soil pressure sensors. Numerical modelling of these shaking table tests is carried using FLAC. Numerical model is validated by comparing physical model results. Responses of wrap faced walls with different number of reinforcement layers are discussed from both the physical and numerical model tests. Results showed that the displacements are decreasing with the increase in number of reinforcement layers while acceleration amplifications are not affected significantly.

Contolling Alkali Induced Heave in soil with fly ash

The properties of the soils can change drastically due to the presence of contaminants leading to several geotechnical failures founded on them. One important pollutant that can have considerable effect is the alkali released from varies industries. It is known that alkali solutions can increase the swelling of soil containing both expansive and non-expansive minerals.Many attempts to control this alkali-induced heave in soils through chemical agents were not successful. With a view to study the use of fly ash to stabilize alkali contaminated soil, the behavior of soils containing 25% and 50% of fly ash has been studied in the presence of 2N-alkali solution. Results of volume change behavior of non-expansive soil containing kaolinite clay mineral in the presence of fly ash showed that it is effective to control the alkali induced swelling in the soil. The effectiveness increases with an increase in the percentage of fly ash in soils. Detailed X-ray diffraction and SEM studies showed that the mineralogical changes that occur in soil due to alkali interaction are inhibited in the presence of fly ash.

Stability numbers for an unsupported vertical circular excavation in c-phi soil

By using an axisymmetric lower bound finite element limit analysis formulation, the stability numbers (gamma H/C) for an unsupported vertical circular excavation in a cohesive-frictional soil have been generated. The numerical results are obtained for values of normalized excavation height (H/b) and friction angle (phi) greater than those considered previously in the literature. The results compare well with those available in literature. The stability numbers presented in this note would be beneficial from a design point of view. (C) 2011 Elsevier Ltd. All rights reserved.

Soil and Groundwater Pollution from Agricultural Activities

This book introduces the major agricultural activities in India and their impact on soil and groundwater. It lists the basic aspects of agricultural activities and introduces soil properties, classification and processes, and groundwater characteristics, movement, and recharge aspects. It further discusses soil and groundwater pollution from various sources, impacts of irrigation, drainage, fertilizer, and pesticide. Finally, the book dwells upon conservation and management of groundwater and soil.