Large-scale direct shear test on the interface between geogrid and gravel-soil mixture
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摘要:
土工合成材料在各类加筋土工程中运用时,面临的问题主要是加筋体结构的稳定性、安全性及长期服役性能,而筋土界面摩擦特性对加筋体结构的稳定性与安全性有着直接的影响。目前对黏土和砂土的研究居多,针对现场常见的碎石土混合料与格栅界面相互作用的研究却鲜有报道。本文以兰州至海口高速公路广西南宁经钦州至防城港段改扩建工程项目为背景,通过室内大型直剪试验对碎石土混合料与土工格栅界面的剪切特性进行了相关研究,探讨了不同剪切速率、压实度、法向应力对直剪界面相互作用特性的影响。结果表明:在法向应力σv≤30 kPa时,界面剪切应力峰值随压实度的提高呈现出线性增长趋势,随法向应力进一步增加,增长趋势由线性增长向折线增长转变;随剪切速率的增加,其在剪切速率v=1.5 mm/min下界面剪切应力最大;界面似黏聚力随压实度的提高而增大,而界面似摩擦角正好与之相反;不同剪切速率下的界面似黏聚力与似摩擦角呈现一定范围内的波动变化,波动范围分别为38.725~50.495 kPa和25.873°~ 29.683°;筋土直剪界面的直剪曲线呈现应变硬化的特征,且不同影响因素下拐点所对应的剪切位移大多集中在剪切面长度的0.83%~1.83%之间。研究结果可为以碎石土混合料作为填料的加筋工程建设提供设计参数及理论参考。
Abstract:When geosynthetics are used in various types of reinforced soil projects, the main problems are the stability, safety and long-term service performance of the reinforced structures. The friction characteristics of the reinforced soil interface have a direct impact on the stability and safety of the reinforced structures. However, there are many researches on clay and sand, and there are few reports on the interface interaction between gravel soil mixture and geogrid. In this study the reconstruction and extension project of Lanzhou-Haikou expressway from Nanning to Fangchenggang in Guangxi is taken as the background, the indoor large direct shear test of the gravel-soil mixture and geogrid interface shear characteristics are studied, and the effects of the different shear rate, degree of compaction and normal stress on the interaction characteristics of direct shear interface are discussed. The test results show that when the normal stress σv ≤30 kPa, the peak value of the interfacial shear stress presents a linear growth trend with the increasing compaction degree. With the further increase of normal stress, the growth trend changes from linear growth to polygonal growth. With the increasing shear rate, the shear stress at the interface between the reinforcement and soil is maximum at the shear rate v =1.5 mm/min. The interfacial cohesion increases with the increasing compaction degree, and the interfacial friction angle is just the opposite. Under different shear rates, the interfacial cohesion and friction angle fluctuate within a certain range of 38.725 kPa to 50.495kPa and 25.873° to 29.683°, respectively. The direct shear curve of the reinforced-soil direct shear interface is characterized by strain hardening, and the shear displacement corresponding to the inflection point under different influencing factors is mostly concentrated between 0.83% and 1.83% of the shear area length. The results can provide design parameters and theoretical reference for reinforced engineering construction with gravel - soil mixture as filler.
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Key words:
- reinforcement-soil interface /
- geogrid /
- direct shear test /
- normal stress /
- shear rate
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表 1 土工格栅的具体物理指标
Table 1. Specific physical indicators of geogrids
产品
规格极限抗
拉强度/
(kN·m−1)极限荷载
下延伸率/%2%延伸率
抗拉强度/
(kN·m−1)5%延伸率
抗拉强度/
(kN·m−1)网孔
尺寸/
mm×mm纵/横向 纵/横向 纵/横向 纵/横向 TGSG
505051.1/51.7 12.1/11.7 18.6/20.7 33.1/35.8 40×40 表 2 试验方案
Table 2. Test Schemes
填料类型 压实度
λ法向应力
σv/kPa剪切速率
v/(mm·min−1)现场碎石土混合料 0.76 15,30,45,60 1.5 0.86 15,30,45,60 0.96 15,30,45,60 0.5,1.5,3.0,5.0,7.0 -
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