Abstract
There are a large number of high-filled and deep-dug highways in loess areas. The differential settlement between the filled and undisturbed soils is the main cause of damage. Bamboo grids are good reinforcement and flexural tensile materials for highway subgrades, and the properties of the interface between the bamboo grid and loess soil affect the safety and stability of embankments. First, the feasibility of bamboo grid application in high-filled embankments in loess areas was verified based on a durability analysis and test of the mechanical properties of bamboo. Then, a series of large-scale direct shear tests were carried out to determine the shear properties of the interface between bamboo grids and loess soils. The influential factors of vertical stress, shear rate, grid spacing, and compactness on the shear properties were studied, and the related mechanism was discussed. The results show that bamboo grids enhance the shear strength of loess soils more than geogrids under different vertical stresses because of the passive friction resistance between the vertical and horizontal ribs and soil particles, the bite force of particle skeletons, and the surface friction of grids. Bamboo grids enhance the stability and shear resistance of soils because of their good deformation performance, and thus, the shear rate effect within 7 mm/min can be negligible. The greater the relative compaction of the subgrade soil, the better the reinforcement effect owing to the greater cohesive force, greater internal friction angle, and better bite force. The variation in grid spacing changes the embedded effect of soil, side friction resistance, and size of the contact area. The shear resistance has an optimal value, which first increases and then decreases. Therefore, in practical applications, it is necessary to test the optimal bamboo grid spacing for a project.
Highlights
China has the most widely distributed and largest loess plateau in the world, comprising various landforms such as loess tablelands, beams, ridges, hills, and gullies.erefore, many high-filling and deep-excavation subgrades are necessary for highway construction in the loess distribution areas (Figure 2). e uneven settlement of the filled subgrade soils and undisturbed subgrade soil is the main cause of highway damage. e conventional method uses geosynthetics such as geogrids and geocells to restrain the local and uneven settlement of embankments [1,2,3]
Large-scale direct shear tests with different vertical stresses, shear rates, grid spacings, and fill densities were conducted according to the interface characteristics of loess reinforced with bamboo grids
A series of large-scale direct shear tests were carried out to study the shear characteristics of the interface between bamboo grids and loess, and the related mechanisms were discussed. e conclusions are as follows: (1) e results show that bamboo grids have good bending resistance, making them suitable for the interface of high and steep slopes to prevent soil sliding. e mechanical properties of the bamboo grids are good, and they meet the specification requirements. e durability of bamboo grids through chemical anticorrosion treatment can meet the need of the project. erefore, it is feasible to apply them into the reinforcement of high-filled loess subgrades
Summary
China has the most widely distributed and largest loess plateau in the world, comprising various landforms such as loess tablelands, beams, ridges, hills, and gullies (see Figure 1). Bamboo has always been a good tensile reinforcement material [6, 7], which has good mechanical properties and can be made in local regions and meet the requirements of “low carbon.” [8] Among them, Phyllostachys pubescens and Neosinocalamus affinis are commonly used in engineering. Bamboo tendon grating is a good reinforced flexural tensile material for subgrade soil, which has received much attention. Ere have been many studies on the mechanical properties of bamboo-reinforced soil and its interaction with soil, but there are few studies on its interface characteristics, especially the influencing factors and laws of loess interface. The interface characteristics of bamboo-reinforced soil directly affect the safety and stability of subgrade On this basis, this paper studied on the characteristics of the interface between bamboo grids and reinforced soil of high-filled embankments in loess areas. A large-scale monotonic direct shear test was carried out. e influential factors such as vertical stress, shear rate, grid spacing, and packing compactness on the development law of shear stress and shear strength were analyzed, and the related mechanism was discussed
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