Abstract
In this paper, three different rock‐soil mixtures were reconstituted in laboratory, which were designed to mimic the proportions of coarse and fine particles in the high fill used at the airport construction sites. The shear strength of the reconstituted mixtures was determined by both large‐scale direct shear tests (DSTs) with different plate opening sizes and triaxial compression tests. By comparing the test results, the most appropriate plate opening size for DSTs on coarse gap‐graded rock‐soil mixtures is discussed. The test results indicate that the opening size has a significant effect on the measured shear strength of gap‐graded rock‐soil mixtures. For DSTs under the same normal stress, the peak strength decreases with increasing plate opening size. For the gap‐graded mixture with a small proportion of coarse particles, a plate opening size of one‐third to one‐quarter of the maximum particle size (dmax) is suitable. With a higher coarse particle content, the opening size should be increased appropriately. If the percentage of gravels (5.0 mm < d < 20.0 mm) is more than 47%, a plate opening size of slightly greater or less than one‐half dmax is more appropriate.
Highlights
With the rapid economic development in China, many airports are being built in southwestern China (Figure 1)
Large-scale DSTs and medium-scale triaxial compression tests were both carried out on the gap-graded rock-soil mixtures G1, G2, and G3. e failure envelopes are plotted for the triaxial compression tests, which are compared with the peak shear strength determined by the DSTs with reasonable opening sizes. e results are described below
Three types of rock-soil mixtures were tested by DSTs and triaxial compression tests. e mixture G1 was obtained by adding some gravels to a fairly large volume of fine particles, and the fine particles completely enclose the coarse particles. e mixture G2 l had a higher proportion of coarse-grained particles
Summary
With the rapid economic development in China, many airports are being built in southwestern China (Figure 1). Compared to costly and time-consuming triaxial compression tests, the DST is one of the most effective methods to determine the shear strength index of coarse-grained materials [2,3,4,5,6,7,8] It is one of the two strength test methods recommended by “Code for Geotechnical Engineering Design of Airport” MH/T 5027-2013 [1] for stability analysis of high fill airport slopes. Erefore, in order to study the shear strength of a gap-graded rock-soil mixture in depth, the DST opening size is an important issue, which needs to be solved for the optimal design and continued construction of high fill airports in China. E shear strength of the gap-graded rock-soil mixtures was measured by large-scale DSTs with different opening sizes. By comparing the results obtained by DSTs and triaxial compression tests, the most appropriate DST opening size for the rock-soil mixtures was determined. is research can provide some reference for the design and construction of similar high fill projects
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