Sliding surface method

static finite element method and dynamic finite element method from nuclear power standard are introduced in detail.By using the geotechnical engineering software Geo-slope we make a seismic stability analysis of diversion dike

which is based on north diversion dike of water intake channel for Tianwan nuclear power unit 5-8

with these three kinds of methods we obtain the safety coefficient and the location of the sliding surface under the effects of ground motion SL-1and ground motion SL-2.The safety coefficient is greater than 1for SL1

in view of the situation that the safety coefficient is less than 1and transient instability of diversion dike happens

Newmark slip analysis is carried out.Further more

applying dynamic effective stress analysis method to overcome the shortage of Newmark slip analysis due to the existence of liquefaction and in order to get the permanent deformation of the diversion dike.The results show that under the ground motion SL1

the overall stability of diversion dike is great;Although the transient instability occurs under SL2

it doesn’t affect the normal use of nuclear power equipment because of the small deformation.The calculation method and the analysis results have certain guidance and reference for seismic stability analysis of some other similar diversion dike structure of nuclear power plant.