STREBGTH BEHAVIOR OF ROCK DEBRIS HEAPS WITH DIFFERENT DENSITIES IN YIBA EXPRESSWAY

Heap(or talus) refers to the accumulation of loose material lies in hillside toe or gentle slope that rock materials are handled by gravity. The proposed appropriate highway route schemes through many large broken rock debris stockpiles(or heaps).The geological conditions are complicated. The compaction degrees of rock piled masses everywhere are also not identical. The strength and stability of different compaction degrees of rock debris piled masses are different greatly. They have huge disadvantages to the project construction. For this reason, experiments of large direct shear strength characteristics of rock debris piled masses with same water content and different densities are carried out. The result shows the follows. The evenness of heap mass moisture contents and densities are very poor. The rock heap filling and cementing content moisture are about 5%~7%.The average water content is 6.5%.The maximum of dry density is 2.25gcm-3.The average of natural density is 2.11gcm-3.The average of dry density is 1.98gcm-3.The samples in low vertical pressure(50, 100, 200kPa) appear the shear stress peaks 116, 154 and 211kPa respectively when the dry density is 2.10g cm-3.The other results show that the shear stress increases with the shear displacement, has no clear peak, and displays strain hardening characteristics obviously. The parameters of rock mass' direct shear strength(c and )increase with the dried density. The general rock heap mass with the same water content is more reinforced when the shear strength is higher. The sensitivity of shear strength to compactness falls drastically with the increase of rock heap mass density in the original gradation and different dry densities.