Stability Reliability Analysis For The High Loess Slope At The Site Of The Proposed Huan Xian Electric Power Plant

The proposed Huaneng power plant in Huanxian was constructed on the site wherethe loess ridge slope had been excavated and flattened. Loess high slopes, of which thehighest height measured to190meters were formed at the trailing edge, so the stability ofslopes become the key issue of the project. In this paper, the reliability analysis wasconducted on the whole stability of the excavation scheme on the basis of investigation andlaboratory test, and the local stress concentration and large displacement zones wereconfirmed by the finite element analysis, then the excavation scheme which meeting theslope stability and the local regulation measures were proposed. The work carried out inthis paper as follows:（1） The profiles of22slopes that in limit state were measured, based on theengineering analogy, according to the relationship between gradient and height of slopes inlimit state measured near the site, the initial slope cutting scheme is proposed, with sloperatio1:2.25and1:2.50respectively.（2） According to the physical and mechanical properties and the material compositionof soil, the slope stratum can be classified into5groups: Q₃₊₂collapsible loess; Q₂non-collapsible loess; Q₁loess; Q₁saturated loess; K1sandstone and mudstone, and thegeological model was established.（3） Taking the strength parameters c and φ, which all obey the lognormal distribution,as random variables. The stability formula from Moegentern-Price method was taken asthe limit state equation,10000specimens of c and φ were extracted by Monte-Carlomethod and then combined randomly to calculate the stability coefficients, and then thereliability was analyzed.（4） Considering nature, rainfall, earthquake, rainfall and earthquake4conditions, thereliability analysis on stability of2cutting slope ratio that are1:2.25and1:2.50wasconducted, and the stability coefficient and failure probability were obtained. The result ofcombined analysis shows that the cutting scheme with slope ratio1:2.25is morereasonable.（5） The selected scheme was simulated by2D finite element method, the strain field,stress field and displacement field of the slope were obtained, and the stress concentrationand large displacement zones were conformed, which can provide slope design with basis.（6） According to the difference of slope stratums, the scheme of steps type anddifferent slope ratio was proposed. The scheme suggests that the step height is10metersand the width of the platform is5meters. According to the given safety coefficient, the stable gradients of the main loess layers were calculated inversely as: collapsible loess(Q₃₊₂),50.1°; non-sluming loess （Q₂）,28.2°; and calcareous loess （Q₂）,26.9°.