Abstract
This study focused on the changes of the compaction of the reclaimed soil after the reclamation process and the one-year maintenance period of the nonmetallic mines in north foothills of Tianshan Mountains in Xinjiang. The plate load experiment method was employed to simulate the compaction effect of various times of compaction from the reclamation machine on a different thickness of the reclaimed soil. The experimental data were analyzed by multivariate statistical analysis. The experimental results showed both compaction frequency and thickness of the reclaimed soil were key factors affecting the compaction of the reclaimed soil, and the interaction between them had a dramatic impact on the soil compaction. The difference of the porosity between the three-time compacted soil by the compaction machine and the noncompacted soil was significant. The effect of a single compaction dampened with the increasing times of compaction. The porosity of the 50 cm and 70 cm thick topsoil continuously decreases with the increasing times of compaction at the depth of 10 cm from the surface soil. The porosity at the 30 cm depth of the 50 cm and 70 cm thick topsoil decreased first and then increased with the increasing times of compaction. At the end of the one-year maintenance period, samples from different depths of the reclaimed soil of various thicknesses were collected to investigate the changes of porosity. The results showed the porosity of the reclaimed soil at different depths was changed due to irrigation. The porosity of the uncompacted soil decreased progressively from the surface to the deep region. The porosity of the compacted soil at the 10 cm depth was lower than that at the 30 cm depth due to soil sealing, whereas the porosity decreased with the increasing depth in the deeper region. The results from this study could provide a fundamental reference for the reclamation of nonmetallic mines in northern foothills of Tianshan Mountains in Xinjiang, China.
Highlights
Introduction e northern foothills of Tianshan Mountains in Xinjiang are one of the key developmental and constructional areas of the national “Belt and Road” initiative. e area is rich in nonmetallic minerals. ere were about 260 nonmetallic mining permits issued by the Department of Land and Resources of the Autonomous Region, which accounted for 58% of the total number of permits issued in Xinjiang. e massive exploitation of mineral resources will inevitably cause extensive damages to the local geological and ecological environment, resulting in the large-scale destruction of land resources and vegetation on the surface
The open-pit mining of nonmetallic mines in this region had resulted in the destruction of about 555 km2 of land resources, not including the sandstone ores managed by various counties and cities. e nonmetallic mining is done using the open-pit mining approach
It is still elusive to utilize the plate load test to simulate the compaction effect of the reclaimed soil of a different thickness filled with large blocks of hard waste rocks in the nonmetallic mines area
Summary
E lower part of the reclaimed soil was backfilled with waste rocks from this limestone mining area. It is still elusive to utilize the plate load test to simulate the compaction effect of the reclaimed soil of a different thickness filled with large blocks of hard waste rocks in the nonmetallic mines area. E hydraulic jack pressure simulation was utilized to analyze the characteristic changes in density and porosity of the reclaimed soil using a compaction machine (crawler-type bulldozer), different compaction times (1 time, 3 times, and 5 times), and different topsoil thickness (30 cm, 50 cm, and 70 cm). E experiment was designed to collect samples at the depths of 10 cm and 35 cm, respectively, to represent the changes in porosity of the reclaimed soil at different depths. A cylindrical metal barrel with a bottom area of 2 m2 was used as the testing pit (Figure 4). e depth of the barrel was 2 m. e limestone waste rocks were backfilled at the bottom of the barrel. e upper part of the barrel was backfilled with 30 cm, 50 cm, or 70 cm reclaimed soil according to the initial design. e device used in the plate load test was utilized to compact the topsoil for 1, 3, and 5 times. ree ring-shaped knives were used to take three original samples at the depths of 10 cm and 30 cm, respectively. e base where the experiment was performed had a limited number of test barrels. e six barrels were divided into 2 groups in the test to observe the effect of soil
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