摘要
针对山区风化岩质路堑边坡易产生崩塌、坠落、坡面冲刷及坡顶堆积失稳等工程问题,依托河北省大广公路蒙冀界至承德段高速公路建设工程,选取K96+265~K96+450段岩质路堑边坡开展了柔性支护结合厚基材生态防护技术室内试验研究,以期为实际工程提供参考和依据。
1)通过岩石的室内物理力学性质试验,得到其崩解指数为43.03%,天然、烘干和饱水状态下的单轴抗压强度分别为27.61MPa、23.68MPa和1.23MPa,粘聚力为1.52MPa,结果表明该岩体属于软质岩,易风化失稳。
2)通过钢丝网拉伸性能试验,得到双绞合钢丝网和HEA钢绳网的抗拉强度分别为453.2MPa和1973.2MPa,弹性模量分别为0.85GPa和14GPa,延伸率分别为21.3%和25.2%,结果表明钢丝网具有较高的抗拉强度和良好的柔韧性。
3)通过室内土工试验,分析了用于厚基材的基质土和表层土的物理力学性质。结果表明,两种土质均属于低塑性粉质粘土。通过厚基材的无侧限抗压强度试验以及室内模拟试验,确定了厚基材各种材料的最佳掺配比例为土∶水泥∶肥料∶纤维∶保水剂=90.997%∶6%∶1%∶2%∶0.003%,同时确定护坡基材平均厚度不低于8cm,生长基材的厚度为2cm。
4)根据现场调查、室内试验结果和相关文献资料,确定了试验路段所采用的柔性支护方案为:主锚杆+纵横向支撑绳+钢绳网+双绞合钢丝网,并用Φ8mm钢丝绳进行缝合,使钢绳网块紧贴坡面。经验算得到,挂网后边坡的安全系数F '=2.13,相对于未挂时提高了53.3%,说明挂网极大地提高了边坡的稳定性。
5)通过总结分析柔性支护系统和厚基材生态防护施工工艺,提出了相应的施工注意事项和施工质量管理要求。
总之,本文的研究结果为柔性支护技术推广应用积累了经验,可供同类工程参考。
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.
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