Experimental Research On Technology Of Flexible Retaining With Thick Substrate Ecological Protection For Rock Cut Slope

According to the engineering problems such as collapse, rockfall, slope wash,deposit instability on top of slope and etc in the weathered rock cut slope of mountainarea, and relying on the construction project of expressway from the border betweenInner Mongolia and Hebei to Chengde City in Daguang Highway, the section ofK96+265~K96+450for rock cut slope was selected to develop the laboratory researchon technology of flexible retaining with thick substrate ecological protection in orderto provide a reference and basis for the actual project.1) Through the laboratory tests of physical and mechanical properties of therock, the slaking index is43.03%, the uniaxial compressive strength under the state ofnatural, drying, water-saturated are27.61MPa,23.68MPa and1.23MPa, respectively,and the cohesion is1.52MPa. The results show that the rock belongs to the soft rock,and it is easy to weathering instability.2) Through the tests of tensile performances for the steel wire mesh, the tensilestrength, the elastic moduli and the elongation rates of the double twisted steel wiremesh and the wire net of HEA are453.2MPa and1973.2MPa,0.85GPa and14GPa,21.3%and25.2%, respectively. The results show that the steel wire mesh is higher intensile strength and well in flexibility.3) Through the laboratory tests of the soils, the physical and mechanicalproperties were analyzed for the substrate soil and the surface soil of thick substratematerial. The results show that the both soils belong to low plastic silty clay. Throughthe tests of unconfined compressive strength and indoor simulation for the thicksubstrate, the optimum mix ratio of the thick substrate was determined as soil:cement: fertilizer: fiber: water retaining agent=90.997%:6%:1%:2%:0.003%.The average thickness of the slope protection substrate is not less than8cm, and thethickness of the growing base material is2cm.4) According to the field investigation, the laboratory tests and the relativeliteratures, the flexible retaining scheme in the trial road section was determined as:main anchor+longitudinal and horizontal supporting rope+steel wire net+doubletwisted steel wire mesh, and the system is stitched with the steel rope of Φ8mm and tomake the steel rope blocks close to the slope. The checking calculation was putforward to obtain the safety coefficient as F'=2.13after hanging the systems, and the safety coefficient increases by53.3%for without hanging the system. It indicatesthat the hanging has greatly improved the slope stability.5) The corresponding construction considerations and the construction qualitymanagements were put forward in accordance with the summarization and analysis ofconstruction technique for flexible retaining system and thick substrate ecologicalprotection.In summary, the researches can accumulate the popularization experiences forthe flexible retaining technology and provide a reference for the similar projects.