露天矿区生态地质层修复中地形重塑层的构建技术及应用

Construction and restoration technology of terrain remodeling layer in the restoration of ecological geological layer in open-pit mining areas

  • 摘要: 露天地区矿山开采容易形成不规则采坑、高陡边坡和渣山、原始土壤破损、采坑积水等一系列地貌形态的改变,造成与周边环境的不协调。不仅影响地表生态环境,还会对地下浅层水渗流场、冻土层等带来不同程度的影响和破坏,且存在滑坡、垮塌等地质隐患和灾害。针对这些问题,从地质角度提出通过构建地形重塑层实现开采后矿山地形地貌重塑的思路与方法,应用形成的地形重塑层修复关键技术,在青海木里高原高寒露天矿区生态环境治理与修复中取得显著效果。首先定义地形重塑层,即是对地貌起伏形态、采坑和渣山边坡等的稳定性和安全性起控制作用的复杂成形曲面。地形重塑层是一个复杂不规则且动态变化的重构层,是生态地质层修复的一种情况。提出地形重塑层的构建思路与方法:(1)通过空−天−地一体的地质勘查与监测手段,对矿山开采后的采坑、采坑边坡和渣山等情况进行系统的勘查、监测和评估。(2)根据治理对象的不同,对修复的目标地质体进行分类,本次依据边坡坡体岩性变化和岩层倾向与坡向的关系,将岩质边坡分为4类13型。(3)通过理论计算结合现场勘查测量,确定不同修复地质体的地形重塑层形态与产状。(4)通过覆土复绿,实现采坑、渣山依形就势的综合治理和矿山地形地貌的修复。以青海木里矿区为例,系统论述了地形重塑层构建与修复技术:对采坑坑底的修复,考虑挖损采坑深度和地形现状,设计合理的坑底样式,防止出现二次滑坡或坍塌等地质灾害;对边坡治理与修复,通过理论计算和野外现场观测,确定木里矿区边坡稳定的合理坡角应小于26°,治理时根据不同岩质边坡类型,采用清坡处理、修筑台阶状边坡等方法,保证采坑边坡稳定和后期植被复绿;对于特殊的渣山边坡治理,需要通过构建坚硬的地形重塑层,形成类似鸡蛋壳一样的渣山外壳,以起到稳定地形地貌、防止水土流失和涵养水源的作用。利用遥感影像数据对比治理效果,治理前矿区地形杂乱,边坡坡角大且不稳定,植被退化,经地形地貌重塑治理后,矿区边坡的坡角基本都处于26°以下,植被长势良好,治理效果显著。提出的地形重塑层构建方法和修复技术为高原高寒矿区生态治理和矿山地形地貌的修复提供了新的治理思路与方法。

     

    Abstract: Mining can easily result in a series of change in the geomorphic form, such as irregular mining pits, high and steep slopes, slag hills, primitive soil failure and accumulated water in mining pits in the plateau and alpine mining area, which is in disharmony with the surrounding environment. Such changes of geomorphic form will not only adversely affect the surface ecological environment, but also bring different degrees of influence and damage to the shallow groundwater seepage field and the permafrost. In particular, the geological hazards and disasters such as landslides and collapses may even be resulted in. In response to these problems, the author put forward the idea and method of remodeling the mine landform after mining by constructing the terrain remodeling layer from the geological perspective. The key restoration technique of terrain remodeling layer was applied to the ecological environment governance and restoration in plateau and alpine open-pit mining area of Muli in Qinghai, with remarkable results achieved. Firstly, the terrain remodeling layer is identified, which is the complex shaped surface that plays a decisive role in controlling the stability and safety of terrain undulation, mining pits, and slag hill slopes. Definitely, the terrain remodeling layer is a complex, irregular and dynamically changing remodeling layer, which is a case of eco-geological restoration. Herein, the construction idea and method of terrain remolding layer was proposed as follows. (1) The mining pit, its slope and the slag hill after mining are systematically investigated, monitored and evaluated through the air-space-ground integrated geological exploration and monitoring. (2) The target geological body to be restored is classified based on the different restoration and governance objects. Here, the rock slopes were classified into 4 categories and 13 types by the changes in the lithology of the slope and the relationship between the inclination of the rock layers and the slope direction. (3) The morphology and occurrence of terrain remodeling layers for different restored geological bodies are determined through the theoretical calculations and field survey. (4) The comprehensive management of the mining pits and slag hills, as well as the restoration of mining terrain and landforms, can be achieved by soil covering and greening according to the field conditions. In this paper, the construction and restoration technology of terrain remolding layer was systematically discussed based on Muli mining area in Qingdao. For the restoration of the mining pit bottom, a reasonable bottom pattern should be designed with consideration to the depth of the damaged mining pit and the current condition of the terrain, so as to prevent the occurrence of geological disasters such as the secondary landslide or collapse. For slope treatment and restoration, it was determined through theoretical calculation and field observation that the reasonable slope angle should be less than 26° for the slope stability in Muli mining area. For slope treatment, the methods, including slope cleaning and building of step slope, should be adopted according to different types of rock slope, so as to ensure the stability of mining pit slope and later vegetation greening. For the treatment of special slag hill slope, it is necessary to form a shell of slag hill like an egg shell by building a hard terrain remodeling layer, to stabilize the terrain and landform, prevent soil erosion and conserving water sources. Comparison of the treatment results with the remote sensing image data before and after the mining area treatment shows that: the terrain of the mining area was disordered, the slope angle was large and unstable, and the vegetation was degraded before treatment. However, the slope angle of the mining area is basically below 26° and the vegetation grows well after the topographic and geomorphic remodeling, indicating a remarkable result of treatment. Generally, the construction method and restoration technology of terrain remolding layer proposed in this paper provide a new idea and method for the ecological management of plateau and alpine mining areas and the restoration of mine topography.

     

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