格栅横肋形状对加筋风积沙界面剪切强度的影响

The influence of transverse rib shape on the interface shear strength of geogrid reinforced aeolian sand

关键词:  土工格栅  格栅横肋  界面剪切强度  拉拔试验  离散元-有限差分耦合技术

Key words:  geogrid  geogrid transverse ribs  interface shear strength  pull-out test  DEM-FDM coupling technique

摘要:

为提高土工格栅对加筋风积沙的嵌固作用,在普通双向格栅的基础上,通过改变横肋的厚度和形状,设计了4种新型横肋结构的土工格栅；采用拉拔试验和离散元-有限差分耦合的方法,研究了土工格栅横肋形状对风积沙加筋效果和机理的影响,并引入了加筋效率评价筋土界面阻力,确定了加筋风积沙的最优格栅横肋形状。在宏观层面上分析了不同横肋厚度和形状下拉拔力与拉拔位移的关系及加筋效率,细观层面上研究接触力链和位移场的演化规律。研究结果表明:横肋的形状和厚度对筋土界面抗剪强度影响很大,4种新型横肋结构的格栅拉拔力约为普通双向格栅的1.1~3.6倍,结合格栅用料比的概念,得到菱形横肋结构的格栅加筋效率最高。通过细观分析发现,在拉拔过程中,拉拔端的强接触力链明显变密集；与普通双向格栅相比,菱形横肋结构格栅周围土体的接触力链演变趋势更为显著,强应力链也更为密集,说明横肋形状的改变能够调动更多的土颗粒抵制格栅的拔出。拉拔过程中土颗粒的位移相对于格栅的位移存在滞后性,相同拉拔位移下,菱形横肋结构的格栅周围土体参与度更高,对土体的扰动也更大。

Abstract:

In order to improve the embedding effect of geogrid on reinforced aeolian sand, in this paper, four kinds of geogrids with new transverse ribs are designed by changing the thickness and shape of transverse ribs on the basis of ordinary biaxial geogrid. The pull-out test and DEM-FDM coupling method are used to study the influence of grid transverse ribs on the reinforcement effect and mechanism of aeolian sand. The reinforcement efficiency is introduced to evaluate the interface resistance characteristics of geogrid and soil, and the optimal geogrid transverse rib shape of reinforced aeolian sand is determined. The relationship between pullout force and pullout displacement and reinforcing efficiency under different thicknesses and shape of transverse ribs are analyzed at the macroscopic level. The evolution law of contact force chain and displacement field is studied at the mesoscopic level. The results show that the shape and thickness of the transverse ribs have a great influence on the shear strength of the reinforcement-soil interface. The pull-out force of the four new types of geogrids is about 1.1-3.6 times that of the ordinary biaxial geogrid. Combined with the concept of the material usage ratio of the geogrid, it is found that the rhombus transverse rib geogrid has the highest reinforcement efficiency. Through microscopic analysis, it is found that the strong contact force chain at the pull-out end is obviously denser during the pull-out process. Compared with the ordinary biaxial geogrid, the evolution trend of the contact force chain of the rhombus transverse rib geogrid is more significant, and the strong force chain is more denser, which indicated that the change of the shape and thickness of the transverse rib can mobilize more soil particles to resist the pull-out of the geogrid. During the pullout process, the displacement of the soil particles is lagging behind the displacement of the geogrid. Under the same pullout displacement, the participation of the surrounding soil of the rhombus transverse rib grid is higher than that of the biaxial geogrid during the pullout process, and the disturbance to the soil is also greater. The findings of this study can offer a significant reference for the development of new transverse rib geogrids and the reinforcement design of desert railway subgrades.