SLOPE STABILITY ANALYSIS OF SUBMARINE CANYON AREA ALONG PIPELINE ROUTE OF LIWAN3-1 GASFIELD

The finite element strength reduction method and limit equilibrium method are used respectively for the slope stabilities of six typical profiles in the submarine canyon area where the submarine pipeline of Liwan3-1gasfield is laid along its seabed. The soil strength characteristic of increase in depth is considered in the slope stabilities models. The comparison result shows that finite element strength reduction method and limit equilibrium method present consistent results. The stability factors obtained by the finite element strength reduction method are most closed to those of the Spencer method, with a relative error of less than 3.5%.All the slopes are basically stable, although some local areas in the middle and lower parts of the canyon with low soil strength and high slope are close to the critical state. The slopes in the upper canyon area have relatively higher stability factors than those in the other areas. The horizontal seismic acceleration can reduce the slope stability factor greatly, and the sliding depth usually increases with the acceleration. When the horizontal acceleration is 0.2g, most slopes in the middle and lower parts of the canyon would fail. The submarine slope angle and the soil strength are the mainly factors which control the slope stability in the canyon area. The stability factor and sliding depth are sensitive to the local slope angle and the strength distribution of the soil. A reasonable slope stability assessment result is dependent on the accuracy of terrain data and soil mechanics parameters.