» عنوان : Soil Dynamics And Earthquake Geotechnical Engineering
زبان PDF : لاتین
تعداد صفحات : ۲۶۸
Liquefaction has become one of the most important and interestingtopics in thefield of geotechnical earthquake engineering. Also, its study became apart and parcel of seismic microzonation considering its severity. The devastationbrought by it due to earthquakes of Niigata (Japan), Bhuj (India), Nepal has turnedthe spotlight on the seriousness with which this hazard has to be considered. So, inthe present study, a comprehensive experimental program was undertaken in whicha series of strain-controlled cyclic triaxial tests were performed to evaluate theliquefaction resistance of local sand in Warangal. Tests were carried out at relativedensities, i.e., 35, 50, and 65%, and reduction in pore pressure with increase inrelative density was observed. Similarly, confining pressures of 100 and 150 kPafor amplitudes ranging from 0.08 to 1% were also considered. From the results, itwas also observed that higher confining pressures resulted in decrease in porepressure whereas higher amplitude of loading resulted in a rise in pore pressure.This proved that densification or increasing confining pressure improves resistanceagainst liquefaction which can be considered as the cheapest soil improvementtechnique to mitigate liquefaction hazards in unconstrained areas.
Construction of structures like buildings, foundations on loose granular soils (likesands) has become a tough task in earthquake-prone areas. This is due to the factthat behavior of soil under static loading is different from dynamic loading. Severalareas in India such as Kashmir, Himalayas, Bihar, Northeast region are frequentlyprone to earthquakes. Moreover, the recent earthquakes like Bhuj, 2001 and Nepalearthquake (2015) which were the most destructive earthquakes in India in the last50 years had caused huge damage. The reconnaissance carried by many peopleshowed that those earthquakes were characterized by widespread liquefaction thatcaused sand volcanoes, ground cracking, lateral spreading, etc. Not only these,there are many other cases also in the past where severe havoc was seen due toinduced liquefaction during earthquakes (Seed and Idriss1967; Sitharam et al.2004; Boulanger et al.1997). This resulted in evaluation of liquefaction potential byseveral researchers either by stress-based (Seed and Idriss1971; Seed1979)orstrain-based (Sitharam et al.2012) approaches. The advantage in adopting astrain-based approach is the total or partial replacement of parameters influencingsoil properties like method of sample preparation, lateral earth pressure coefficientby the shear modulus in calculation of shear strains (Dobry et al.1982). Afieldmeasurement of shear modulus (Gmax) automatically incorporates many of the soilcharacteristics which are necessary for pore pressure buildup during earthquakes.Thus, this approach decreases the need for a detailed knowledge of the site which isessential in the stress-based approach. There are many ways to mitigate liquefactionof which densification is the cheapest technique (Menard and Broise1975; Lyman1942). So, in the present work, an attempt is made in the laboratory to study theliquefaction potential of locally available sand in Warangal and determine the effectof parameters like amplitude of loading, confining pressure, and relative density ondynamic soil behavior.