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土工格栅-黄土界面摩擦特性拉拔试验研究
Experimental Study on Friction Characteristics of Geogrid-Loess Interface
为研究钢塑型土工格栅-黄土界面摩擦特性,利用自主研发的土工合成材料拉伸拉拔试验系统,在不同法向应力、拉拔速率、含水率下开展一系列钢塑型土工格栅-重塑黄土室内拉拔试验。试验结果表明:筋材的拉拔力峰值随着法向应力增大而增大,随含水率的增大而减小,最大值为18.143 kN;最大剪应力随含水率增大而减小,随法向应力增大而增大;界面黏聚力在最佳含水率时,最大为11.043 kPa;似摩擦系数随含水率增大而减小,随法向应力增大而减小,在法向应力为105 kPa时,似摩擦系数约为规范建议值的1/3~1/2。拉拔特性试验表明,在进行工程设计时,应充分考虑含水率、上覆荷载等工程应用条件。研究结果可为黄土高边坡结构设计提供参考。
[Objective] Geogrids are widely applied in high loess slopes engineering due to their advantages of strong overall durability, high tensile strength, and corrosion resistance. The interface friction coefficient between the reinforcement and soil is a crucial parameter for pull-out verification of reinforced soil slopes, and its value is influenced by multiple factors. [Method] This study employed an independently developed geosynthetic material tensile pull-out testing system to conduct a series of laboratory pull-out tests on steel-plastic geogrids and remolded loess under varying normal stresses, pull-out rates, and water contents, aiming to investigate the effects of these factors on the friction characteristics of the steel-plastic geogrid-loess interface. [Results] The peak pull-out force of the reinforcement increased with increasing normal stress and decreased with increasing water content, with a maximum value of 18.143 kN. Under different normal stresses, the relationship between pull-out force and displacement at the loading end was divided into four stages,such as linear increase, nonlinear increase, decay, and stabilization. The pull-out force increased with the pull-out rate, and higher pull-out rates corresponded to greater peak pull-out forces. Although the pull-out rate varied, the trend of the pull-out force versus loading end displacement curve remained similar; as the loading end displacement continuously increased, the pull-out force first increased, then decreased, and finally tended to stabilize. The maximum shear stress increased with normal stress and decreased with water content; the influence of normal stress on maximum shear stress weakened gradually as water content increased. The interface cohesion showed a trend of first increasing and then decreasing with rising water content, reaching a maximum of 11.043 kPa at the optimal water content. The apparent friction coefficient decreased with increasing water content and normal stress; when the normal stress was 105 kPa, the apparent friction coefficient was approximately 0.13, which was about one-third to one-half of the recommended standard value. [Conclusion] The pull-out characteristic tests indicate that engineering design should not be evaluated solely based on the apparent friction coefficient, but should also fully consider actual water content, overburden load, and other engineering conditions. The results of this study provide a reference for the structural design of high loess slopes.
土工格栅 / 拉拔试验 / 法向应力 / 界面特性 / 似摩擦系数
geogrid / pull-out test / normal stress / interface characteristic / apparent friction coefficient
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The stability of high and steep geosynthetic-reinforced slope and the reinforcement mechanism are researched through centrifugal model test and two-dimensional finite element method. Two centrifugal model tests are conducted in the purpose of exploring the failure trend or failure mode through measuring the variation of deformation and soil pressure of both unreinforced and reinforced slopes in stepped loading. Two-dimensional finite element model is established based on the fundamental parameters of the centrifuge model test. The calculation results are compared with the measured centrifugal test results to verify the rationality of the finite element model. Furthermore, the finite element model is employed to analyze the sensitivity of slope stability to the packing intensity and tensile strength of reinforced body. Results show that the geosynthetic reinforcement effectively improves the slope safety factor, but has slight influence on settlement. The failure mode of unreinforced slope differs from that of reinforced slope: collapse occurs at the unreinforced slope abutment, while stress concentrates at the 1/6-1/3 height of reinforced slope.
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