Abstract：The Danba new county town in Sichuan Province is located on the ancient landslide. The potential land for construction is getting relative shortage for the rapid extension of new county town construction since the 1990s. A 28 m high slope that is improperly supported has been cut in the front of the landslide，which triggers the reactivation of the ancient landslide with a volume of 2.5×106 m3；and the maximum displacement is greater than 50 mm/d. The new county town would be destroyed by the landslide if no stabilizing measures were adopted. The issues of deformation，stability analysis and preventing countermeasures of soil-rock mixtures are presented for a new type of landslide structure. An emergent measure had been adopted：sandbags with a volume of 4 000 m3 was consdiered on the foot in front of slope；and then，the displacement was obviously dropped by 5 mm/d，indicating that the sliding was effectively controlled. Meantime，the 5 rows of prestressed cables with 1 300 kN grade are used in the landslide to enhance the stability of landslide. The simulation with FLAC3D was conducted for the factors of safety(FOS) of the landslide under the conditions of nature，cutting，overloading in the front and anchoring with the strength reduction(SR) method. The result shows that the SR method for FOS calculation has good performance with error of 0.1%–4.1% compared with those of Janbu generalized，Morgenstern-Price and Sarma methods. However，the results for slide zone analysis have great errors. The conventional methods for landslide stability analysis have considerable error for landslide with soil-rock mixture，which will give unreasonable parameters for residual shear strength and friction movement of slip zone. The value of friction angle j = 29° instead of j =24°–27° is recommended for soil-rock mixture. In practice，back analysis for friction angle would be 20%–30% greater than the one obtained by residual shear strength test；and it should be also considered for the effect of landslide structure on the stability.
