For ground improvement, assessment of damage during an earthquake is very important issue which in turn depends on the ground motion. The characteristics of an earthquake motion at a site depend on the shear wave velocity (V s ). The shear wave velocity profile at a site may not be readily available however, the numbers of blows (N) from standard penetration test (SPT) are readily available. This paper presents a development of reliable correlation between V s measured by multi channel analysis of surface wave tests and N measured using SPT at various sites in Roorkee region. These tests have been carried out at ten different sites in Roorkee region (within a radius of 30 km). The SPT samples are tested in the laboratory for index properties. Roorkee is situated in high seismic zone, therefore the study is important for this region. Based on the statistical assessments, an empirical correlation between V s and N was developed. This is done separately for all types of soils, sands only and clays only. The developed relations fall within the range of other relations developed worldwide for other sites. A comparison with available relations is also presented. The proposed relations will be helpful in seismic microzonation of the region as ground motion is one of the important parameters.
Before taking up the ground improvement of a site, assessment of liquefaction potential of a region is very important. This also helps in seismic microzonation of the area. It can be rationally performed if the data of site (using either field tests or laboratory tests) are available. The aim of the present study is to evaluate liquefaction potential of Roorkee (India) region. For this purpose the liquefaction resistance of the soil, within the radius of 30 km of Roorkee, was evaluated using two different approaches. First is the field approach based on standard penetration test (SPT) N-Value and second is the laboratory approach employing mean grain size distribution (D 50 ). Investigation was carried out at five different locations by conducting SPT tests and collecting soil samples at regular interval. The cyclic shear stress due to earthquake loading was examined using simplified method as well as using ground response analysis. The factor of safety against liquefaction was evaluated at different depths for all the sites using both field and laboratory data. It was found that the factor of safety against the liquefaction using field approach is marginally greater than that using the laboratory approach for all the sites. Also the factor of safety using ground response analysis is significantly smaller than that using simplified method. Thus it was concluded that use of simplified method may not be adequate.
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