Liquefaction of Sand and its Counter measures
Dr. Shashi Ranjan Kumar, Principal, Jagat Guru Dattaray College of Technology (JDCT), Indore, Dr. Achintya, Principal, Bhagalpur College of Engineering, Bhagalpur.
The liquefaction of sand is one of the primary factors leading to the damage of the structures during earthquakes. The liquefaction normally occurs due to the generation of excess pore pressure under undrained loading in sandy soil. Hence, it is imperative to take countermeasures against liquefaction and suggests the approach to combat it such that while the soil liquefies, the damage is minimum.
Introduction
Over the years, some of the most spectacular, and costly damage to the earth slopes and the foundation of structures has been due to liquefaction of sands during earthquake. When an earthquake shakes loose saturated sand, the grain structure of soil tends to consolidate into more compact packing. Since all these movements happen rapidly, there is no chance to reduce the volume through the dissipation of pore water pressure from within the soil mass. Therefore, the incompressible pore fluid takes up the entire applied stress and consequently, the effective stress approaches zero and ultimately the deposit "liquefies." Since a liquid has no shear strength, occurrences of disastrous consequences due to the failure of earth slopes and foundations are inevitable.
Figure 1: Liquefaction during Bhuj Earthquake (26.01.2001) & Figure 2: Ground Rupture due to Liquefaction near the Epicentre of Bhuj Earthquake (26.01.2001)
