Monitoring soil moisture at different subsidence areas of mining in western windy and sandy region with neutron instrument

In order to research the influence of mining subsidence on soil water content and the variation characteristics of soil water content in windy and sandy region, the authors selected a working face of Da Liuta mining district as the research object, which has the similar characteristics with other mining faces, such as working thickness and mining progress.We divided the subsidence area into pelvic floor area and marginal zone.The pelvic floor area has dynamic fractures which can be quickly closed in the cycle of 18 d.The marginal zone has marginal fractions and additional slopes.And when mining is finished, the marginal fractures are still existing.We used neutron probe method to monitor soil moisture of pelvic floor area, marginal zone and unexploited area.The monitoring depth was 10-200 cm.The monitoring lasted for 2 years.By comparing 2 subsidence areas’ soil water content with unexploited area, we could find the impact law of mining and give feasible advice for land reclamation and ecological rehabilitation in western windy and sandy region.The result showed that: 1) Before exploitation, the study area’s soil moisture content of 10-200 cm depth had obvious layered characteristic, and the depth could be divided into two layers based on the differences of soil water content variation.In 10-60 cm depth, water content increased linearly, and it was then stable and decreased slightly in 60-200 cm depth.2) Mining subsidence could exert influence on soil water content of both the pelvic floor area and the marginal zone.And the influence of mining subsidence on soil water content had obvious leveling and zoning characteristics.Pelvic floor area’s water content decreased in 10-120 cm and increased in 140-180 cm.Meantime, soil water content decreased in marginal zone.In general, the mining subsidence’s influence on marginal zone was greater than the pelvic floor area.3) After mining, the soil water contents of pelvic floor area presented the phenomenon of recovery.Just one year after mining, the water content could be recovered to the one before, and one and a half years or two years after mining, the water content showed the characteristic of being higher than unexploited area.The recovery effect of marginal area’s soil water content was not so obvious.The soil water content at 140 cm depth could recover to the level of unexploited area in one and a half years after mining, but the soil water content of 10-140 cm depth did not eliminate the impact of mining after 2 years.Therefore, while performing land reclamation and ecological rehabilitation on the west windy and sandy coal mining subsidence land, we should implement subarea management.We can make full use of self-reliant ability of pelvic floor area’s soil water content.At the same time, we should adopt artificial restoration measures to restore soil water content of marginal area in time in order to meet the water needs of plant growth.In this way, we can rely on the power of nature as far as possible and implement management purposefully.Not only can it reduce the possibility of secondary disturbance brought by the artificial restoration measures, but it can reduce the cost of ecological restoration.