Research on ground characteristics of permafrost in Mongolia

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During the first year measurement site is set on the designated area to measure seasonal frost heaves in Mongolian ground. Based on the measurement from Oct.2003 to Oct.2004, the following conclusions are obtained :1)large heaves are observed in the ground with high water level, regardless of permafrost's existence.2)Susceptible ground such as clay can yield large heave, while unsusceptible ground such as sand can yield small heave. However, the ground of sand in lower layer and clay in upper layer also can yield much heave because sand layer may promote suction of water to form ice lens in clay layer.3)Slow freezing speed gives large heave.On the other hand, laboratory test on the samples taken from the site is conducted to define frost heave ratio and other parameters in Takashi equation. As a result, it is found that heave of the ground strongly depends on freezing speed. Additionally from the sensitivity analysis for the Takashi equation, it is also found that over load and freezing speed are dominant parameters in the equation.Finally, it can be said that the frost heave estimation can be done by conducting laboratory test on the samples in site, and this fact can be applied to the pipeline design in permafrost area.