Seismic active thrust on rigid retaining wall using strain dependent dynamic properties

© 2018 American Society of Civil Engineers. An analytical model is proposed for the evaluation of seismic active thrust on retaining wall resting on sandy soil. Foundation and backfill soil is idealized as Kelvin-Voigt solid. The governing differential equation of vertically propagating shear wave is solved by maintaining the displacement continuity and stress compatibility at the interface between backfill and foundation soil. Nonlinear distribution of accelerations induced in the backfill soil is then used to compute the seismic inertia force. Total seismic active thrust is obtained by solving the force equilibrium equation of the triangular failure wedge. The present method computes the strain-dependent shear-wave velocity and damping ratio of sand from its modulus reduction and damping ratio curves using an iterative scheme. Amplification and deamplification of the input excitations in the foundation soil and backfill soil are compared with results of dynamic centrifuge tests reported in the literature. An increase in the magnitude of seismic active thrust is observed when the retaining wall is situated on sandy soil in place of the rigid stratum, and the percentage increase is 18% in comparison to the latest method available in the literature. The seismic active thrust values for long period input excitations are nearly 13 to 17% higher compared to short-period input excitations. The parametric study reveals that depth of backfill and foundation soil, impedance ratio, amplitude, and frequency of input motion dominate the response of the backfill soil under seismic condition

Strength Enhancement of Geotextile-Reinforced Fly-Ash-Based Geopolymer Stabilized Residual Soil

© 2020, Springer Nature Switzerland AG. Soils in their natural form are often deemed unsatisfactory to be directly used as a construction material for their respective applications. Under such circumtances, employment of ground improvement techniques to better suit the soil for its function is typically the most economical approach. Consequently, the present research investigated into the beneficial effect of modernized soil treatment techniques, i.e., geopolymer stabilization using fly ash as the precursor and geotextile reinforcement, on the strength enhancement of natural residual soil. A series of unconsolidated undrained (UU) triaxial compression tests were carried out to assess variation of geopolymer stabilized residual soil strength based on the varying number of geotextile layers, geotextile arrangement, and confining pressures. It was found that the increase in the number of geotextile layers resulted in a corresponding rise in soil strength and stiffness. It was also discovered that placement of geotextile layers at sample regions which suffered the maximum tensile stress–strain during loading was more effective compared to random placement. Soil strength was observed to reduce with increasing confining pressure which demonstrated the effectiveness of utilizing geotextile reinforcement at greater depths below the ground to be less. Failure patterns showed that while unreinforced soil resulted in failure along a shear plane at an approximate angle of 45 + φ/2 (φ: angle of internal friction), reinforced samples demonstrated a bulging failure where the soil between adjacent layers of geotextiles appeared to bulge. The findings deemed the employment of geopolymer stabilization and geotextile reinforcement on natural residual soil very effective with regards to the enhancement of soil strength and stiffness

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Not AvailableThe present investigation was conducted for two years (2018-19 and 2019-20) to study the effect of rootstocks (Dogridge, 110R, 140Ru, Salt Creek and own roots of Red Globe) on growth parameters of Red Globe grapevines. The vigour and growth parameters such as pruning weight was found maximum on vines grafted on Dogridge rootstocks while minimum days to sprout and cane maturity was recorded in own rooted Red Globe vines. Number of canes/vine, shoot length, shoot diameter, leaf area and stock: scion ratio varied significantly among the rootstocks and were found maximum in vines grafted on Dogridge rootstock followed by Salt Creek and 110R rootstocks. The present study revealed that Red Globe grapevines grafted on Dogridge followed by Salt Creek rootstock proved better for growth parameters but in terms of growth period Red Globe own rooted vines was early to sprout and took minimum days for cane maturity over the vines grafted on rootstocks.Not Availabl

Components of resistance to sorghum shoot fly, Atherigona soccata

Sorghum shoot fly, Atherigona soccata is one of the major constraints in sorghum production, and host plant resistance is one of the components to control sorghum shoot fly. Thirty sorghum genotypes were evaluated for different mechanisms of resistance and morphological and agronomic traits during the rainy and postrainy seasons. The sorghum genotypes, Maulee, Phule Anuradha, M 35-1, CSV 18R, IS 2312, Giddi Maldandi, and RVRT 3 suffered lower shoot fly damage, and also exhibited high grain yield potential during the postrainy season. ICSB 433, ICSV 700, ICSV 25019, ICSV 25022, ICSV 25026, ICSV 25039, PS 35805, Akola Kranti, and IS 18551 exhibited antixenosis for oviposition and antibiosis against sorghum shoot fly, A. soccata. Leaf glossiness, plant vigor, leafsheath pigmentation and trichomes were associated with resistance/susceptibility to shoot fly. Path coefficient analysis indicated that direct effects and correlation coefficients of leaf glossiness, plant vigor, plant height, plant color and trichomes were in the same direction, suggesting that these traits can be used to select sorghum genotypes for resistance to shoot fly. Principal co-ordinate analysis based on shoot fly resistance traits and morphological traits placed the test genotypes into different groups. The genotypes placed in different groups can be used to increase the levels and broaden the genetic base of resistance to shoot fly. The environmental coefficient of variation and phenotypic coefficient of variation for shoot fly resistance and morphological traits were quite high, indicating season specific expression of resistance to sorghum shoot fly. High broadsense heritability, genetic advance and genotypic coefficient of variation suggested the predominance of additive nature of genes controlling shoot fly resistance, suggesting that pedigree breeding can be used to transfer shoot fly resistance into high yielding cultivars. This information will be useful for developing shoot fly-resistant high yielding cultivars for sustainable crop production