Nihar Ranjan Patra

Cyclic Behavior and Liquefaction Potential of Indian Pond Ash Located in Seismic Zones III and IV

AbstractIn the present study, cyclic behavior and liquefaction potential of pond ashes collected from Talcher, Panki, and Panipat ash embankments located in seismic zone III and IV have been studied. Cyclic triaxial tests were conducted on reconstituted pond ash samples at a relative compaction varying from 94 to 99%. The effects of loading frequency, confining pressure, and relative compaction on cyclic behavior and liquefaction potential of reconstituted pond ashes have been studied. From test results, it is seen that all compacted pond ash samples exhibit good liquefaction resistance, dynamic properties, and degradation index. It may be concluded that pond ashes from Talcher, Panki, and Panipat can effectively be used as a geomaterial in geotechnical applications.

ASSESSMENT OF LIQUEFACTION POTENTIAL OF POND ASH AT PANIPAT IN INDIA USING SHAKE2000

In this paper liquefaction potential of pond ash deposits consists of pond ash and foundation soils have been studied. Two pond ashes namely Unit-I and Unit-II, located at Panipat in India which comes under seismic Zone IV are considered as the part of the study. One borehole was drilled at upstream site of each pond ash and standard penetration tests were carried out at every 1.5m interval up to 40m and 30m depth for Unit-I and Unit-II pond ash respectively. Undisturbed samples were collected by sampling from each bore hole and geotechnical classification tests were performed in the laboratory. The liquefaction analysis of pond ash was carried out by using Seed and Idriss method and 1-D ground response analysis. The ash deposits are found to be loose to medium dense. The pond ash is classified as SMN (Non-plastic sand-silt size fraction). It is concluded that pond ash sites are susceptible to liquefaction for an earthquake of magnitude (Mw) greater than 6.4.

Liquefaction and Earthquake Response Analysis of Panipat Pond Ash Embankment in India

In this study, liquefaction and earthquake response analysis of Panipat pond ash embankment in India has been carried out considering saturated and natural water table conditions. Laboratory and field studies have been carried out to obtain the material properties required for the nonlinear response analysis of the Panipat pond ash embankment. Nonlinear finite element analysis has been carried out by using open system for earthquake engineering simulation (OpenSees). Three earthquakes namely Chamba, Chamoli and Uttarkashi earthquakes have been considered for liquefaction and earthquake response analysis. The standard penetration test (SPT)-N value indicates that the ash deposit in Panipat pond ash embankment is in loose to medium dense state. The excess pore pressure ratio obtained from the analysis is found to be one or more than one below upstream and downstream locations of the pond ash embankment for both saturated and natural water table conditions. The horizontal and vertical displacement is found to be maximum near the toe and first rise slope of pond ash embankment. Hence, ash embankment in Panipat is prone to liquefaction under the excitation of moderate to high earthquake loading.

Static and cyclic properties of clay subgrade stabilised with rice husk ash and Portland slag cement

In the present study, clay soil collected from new Banda, Uttar Pradesh, India has been treated with rice husk ash (RHA) and Portland slag cement (PSC). Based on unconfined compressive strength test results, the optimum mix obtained is of 82.5%Soil+7.5%PSC+10%RHA. The increase in strength of the optimum mix is about 29.8%, 37.2% and 48.55% for a curing period of 7, 14 and 30 days, respectively. The soaked California bearing ratio (CBR) test gives about 91.75% higher values as compared to unsoaked CBR test for a curing period of 30 days. Strain-controlled cyclic triaxial tests were conducted to study the variation of degradation index, shear modulus and damping ratio of the optimum mix with number of cycles for strain amplitudes of 0.4%, 0.6%, 0.8% and 1% and for frequencies of 0.2 and 1 Hz at an effective confining pressure of 100 kPa. It is observed that the degradation index decreases at a fast rate for the first 25–50 cycles. From the study, it is concluded that the aforementioned mix may be suitable for pavement subgrade material.

Assessment of Liquefaction potential of alluvial soil of Indo-Gangetic Interfluves, Northern India

In the present study seismic hazard assessment in terms of ground response analysis and liquefaction potential has been carried out for the Allahabad city, India. The study area is having threat to seismic damage due to Himalayan Frontal Thrust earthquake. Three sites under the study have been characterized by means of in-situ SPT and laboratory tests on representative and undisturbed samples. Three boreholes were drilled at three different locations and SPT blow counts (N) was recorded at 1.5m interval up to a depth of 30m. The liquefaction analysis has been carried out using method suggested by Seed and Idriss (1970). The peak ground acceleration (PGA) values obtained from the analysis were used for the computation of CSR and SPT values for evaluation of CRR. PGA obtained from the analysis ranges from 0.063 to 1.5g. The study revealed that the soil below 10m depth in Allahabad city is susceptible to liquefaction. The post liquefaction settlement analysis of Allahabad soil shows an average settlement of 20 to 70cm.

Shaft Resistance of Piles in Normally Consolidating Marine Clay Subjected to Compressive and Uplift Load

This paper presents 24 test results on instrumented hollow tubular aluminum close ended floating piles in laboratory to examine the mechanisms of load transfer between the piles surface and normally consolidating marine clay. Hollow aluminum tubes of 32mm external diameter and wall thickness of 1mm and length to diameter ratio of 10, 20 and 30 were used as model single piles. Compression and pullout tests were carried out at time periods of 0 to 6hr, 0 to 12 hrs, 0 to 18 hrs and 0 to 24hrs from the time of installation. Multiple neutral planes are observed along the depth of the pile, which is contrary to the present understanding of load transfer. The variation of skin friction with respect to maximum shear strength of soil in undrained condition is about 10 to 200 %. Design stipulations have been proposed based on model tests findings.

Dynamic Behavior of a Geotextile-Reinforced Pond Ash Embankment

ABSTRACT The present study investigates the applicability of woven geotextile in improving the seismic performance of a pond ash embankment located in Renusagar, in seismic zone III of India. Reinforcing materials used are woven geotextiles, placed at 1 and 3 layers of pond ash embankment. To obtain the material models, strain-controlled cyclic triaxial tests had been carried out. A general expression was developed for shear modulus and damping ratio of pond ashes reinforced with and without woven geotextiles considering the data taken from seismic zones of III and IV. The proposed equations have been compared with the reported results of other pond ashes located in India. Finite element model of the pond ash embankment reinforced with geotextiles has been developed. A fluid solid porous material model has been employed to incorporate pore pressure build up during cyclic loading. A parametric study has also been performed to study the effect of reinforcements on the seismic behavior of Renusagar pond ash embankment. Results showed that using the three layers of geotextile, the lateral displacement reduces up to 17%, and the excess pore pressure reduces as much as 30–45%. From the study, it can be concluded that use of woven geotextile in pond ash dykes can be beneficial for its application as reinforcing material in highway embankments, building fills, and earth dams.

Evaluation of residual strength and liquefaction potential of pond ash

AbstractLiquefaction potential of pond ash obtained from the ash pond located at Panki Thermal Power Station, Kanpur, India is evaluated by laboratory static triaxial tests and standard penetration tests (SPT) up to a depth of 20 m. Residual strength approach by Norris et al. (1997) has been used to study the residual state characteristics of remolded ash samples. Consolidated rebounded drained triaxial tests with volume change measurements are performed on the remolded ash samples with three relative densities of 30%, 50% and 75%. The results obtained are compared with the stress-controlled consolidated undrained triaxial test, the method reported by Poulos et al. (1985). It is observed that the liquefaction behaviour can be predicted for 30% relative density within the strain levels. The steady state line obtained from laboratory experiments is compared with the model reported by Cubrinovski and Ishihara (2000). The liquefaction potential based on penetration data is evaluated by the model proposed by S...

Behaviour of piles and pile groups in marine clay under compressive load at various stress conditions

Abstract Experimental investigations on model single piles, line pile groups (2 X 1) and square pile groups (2 X 2) subjected to axial compressive load were conducted in a specially designed triaxial cell with enlarged dimensions in marine clay at vertical and horizontal stress conditions. The variables used in this experiments were embedment length to diameter ratio (L/D = 8.93, L/D = 17.5), spacing of piles in a group (4D, 5D, 6D), controlled horizontal (σH), vertical (σV) stresses (0.03 N/mm2 and 0.06 N/mm2) and pile group geometry / configuration. Parametric study on the influence of the variables involved has been carried out on the load displacement response, tip, shaft, and total resistance and group efficiency of the pile groups. A statistical regression model, based on experimental results, is used to study the variation of efficiency of pile groups with spacing under different vertical and horizontal stress conditions.

Effect of Compressive Load on Uplift Capacity of Single Piles: An Investigation

In this paper, an analytical model has been proposed to predict the net ultimate uplift capacity of single piles embedded in sand subjected to stage compressive loading of 0%, 25%, 50%, 75% and 100% of their ultimate capacity in compression. The following parameters have been considered as variables: density of foundation medium, embedded length to diameter ratio (L/d) of piles, stages of compressive loads. The presence of compressive load on the pile decreases the net ultimate uplift capacity of pile and the decrease depends on the magnitude of presence of the compressive load. It may be due to change in the particle size distribution, soil pile friction angle, or soil compressibility. The change in soil-pile friction angle has been considered in the present model. To validate the model, a comparison has been made with the available laboratory model test results (Dash and Pise2003) and the results obtained from the present model.