A Case Study of the Water Abundance Evaluation of Roof Aquifer Based on the Development Height of Water-Conducting Fracture Zone

New insights into health risk assessment on soil trace metal(loid)s: Model improvement and parameter optimization

Trace metal(loid)s (TMs) in soils may pose potential health risks to humans. Due to model uncertainty and variability of exposure parameters, the traditional health risk assessment (HRA) model may lead to inaccurate risk assessment results. Therefore, this study developed an improved HRA model to assess health risks by combining two-dimensional Monte Carlo simulation (2-D MCS) with a Logistic Chaotic sequence based on published data from 2000 to 2021. The results showed children and adult females were the high-risks populations for Non-carcinogenic risk and Carcinogenic risk, respectively. Meanwhile, children's Ingestion rate (IngR < 160.233 mg/day) and adult females' Skin adherence factor (0.026 mg/(cm2•d) < AF < 0.263 mg/(cm2•d)) were used as recommended exposure to make the health risk within acceptable range. Additionally, when performing risk assessment using actual exposure parameters, priority control TMs were identified, with As being the priority control TM for Southwest China and Inner Mongolia, whereas Cr and Pb for Tibet and Yunnan, respectively. Compared to health risk assessment, improved models increased risk assessment accuracy and provided recommended exposure parameter for high-risk populations. This study will provide new insights for soil-related health risk assessment.

Allocation and Utilization of Coal Mine Water for Ecological Protection of Lakes in Semi-Arid Area of China

In the background of water ecological protection, how to utilize the superfluous coal mine water efficiently has become an urgent problem, especially in northwest China, where the fragile ecological environment needs to be protected but lacks water. To solve this problem, this study proposes a new procedure for the allocation and utilization of mine water aimed at the ecological protection of lakes in an arid and semi-arid area. Based on the water balance method, the ecological water supplement of regional lakes is first estimated according to their different protection goals. Next, a trend analysis of water demand and supply is carried out, and the mine water inflow and available quantity are calculated. Meanwhile, the water resource allocation plan is evaluated systematically. In this study, the procedure is applied to the mine water and lakes in Wushen Banner, Inner Mongolia Autonomous Region of China. The results show that: (1) the lakes can be divided into three classifications according to their ecological protection goals, (2) the available amount of mine water will reach 57.17–81.97 million m3 in 2030, and there are about 46.7 million m3 of water that can be adjusted to reach the optimal utilization in 2020, and (3) the mine water after advanced treatment could meet the requirement of lakes. Finally, it outputs the water supplement path and the water quantity, as well as the water transmission pipelines to each lake, which makes up a new water resources allocation plan and a utilization mode of regional mine water. This utilization mode can provide solutions and ideas for improving the ecological environment of regional lakes and promote the construction of regional ecological safety barriers. Moreover, it can be very helpful for optimizing the allocation of regional water resources, and for improving the reasonable utilization of coal mine water.

Height Prediction and 3D Visualization of Mining-Induced Water-Conducting Fracture Zone in Western Ordos Basin Based on a Multi-Factor Regression Analysis

The mining-induced water-conducting fracture zone (WCFZ) plays a critical role in roof water damage prevention and ecological protection. The measured heights of the WCFZ were collected from 52 working faces or boreholes in the Ordos Basin mining area. Four factors influencing the mining-induced height of the WCFZ, i.e., mining thickness, proportion coefficient of hard rock, working width, and mining depth, were analyzed. The optimal unitary function model of each factor and the height of the WCFZ were obtained through single-factor analysis. The grey correlation method and fuzzy ordered binary comparison method were used to determine the comprehensive weight, and the weighted improved multiple regression model was obtained by combination and iteration. The relative error of the model was basically controlled within 10%. Finally, taking the Qingshuiying Coalfield as an application case, we predicted the mining-induced height of the WCFZ by using the new prediction model. The spatial distribution characteristics of the WCFZ were analyzed by the geographic information system. In addition, Groundwater Modeling System (GMS) software was used to build a 3D structure model of WCFZ height to visualize the spatial distribution rules of the WCFZ. The results showed that the height of the WCFZ can be predicted quantitatively by this new method, and the visualization of the WCFZ can be realized. The proposed method effectively analyzes and predicts the mining-induced height of the WCFZ so that water gushing risks from overlying aquifers can be prevented or mitigated in mines.

Calculation of the Height of the Water-Conducting Fracture Zone Based on the Analysis of Critical Fracturing of Overlying Strata

Accurate division of the water-conducting fracturing zone (WCFZ) in the mining overburden serves as an important basis to evaluate the stability of coal mining under water bodies. Research on the WCFZ is conducive to controlling surface subsidence and realizing safe coal mining under water. Traditionally, the WCFZ is generally determined by field observation (liquid leakage method, borehole television, etc.) or empirical formula. Although these methods boast high accuracy, they are time-consuming and laborious and have some problems such as weak pertinence and a large value range. In this study, a mechanical model under the critical breakage condition of hard and soft strata was established on the basis of the specific geological and mining information of a mine. Besides, the stability condition for the broken strata to form the “masonry beam” structure and the deflection-based bending deformation formula of hard and soft strata were deduced, and the method of calculating the height of WCFZ based on the analysis of critical fracturing of soft and hard strata (hereafter referred to as the CFSHS-based height calculation method) was proposed. Furthermore, with reference to the results of specific engineering tests, the height of the WCFZ in the working face 15,101 of coal mine XJ was analyzed by means of theoretical analysis, numerical simulation and engineering verification, which verifies the rationality and practicability of the CFSHS-based height calculation method.