Shuchen Li

An Attribute Synthetic Evaluation System for Risk Assessment of Floor Water Inrush in Coal Mines

An attribute synthetic evaluation system was combined with attribute mathematical theory and the analytic hierarchy process (AHP) to evaluate the risk of floor water inrush in coal mines. The evaluation indices of floor water inrush were divided into continuous variable indices, which were quantitatively graded according to floor water inrush risk and discrete variable indices, which were qualitatively graded by expert opinion. Single index attribute measurement functions were constructed to calculate the membership degree of the continuous variable indices. The membership degree of the discrete variable indices were evaluated using expert opinion eliciting techniques, such as the Delphi method. The contribution weighting of the evaluation indices were rationally distributed by the AHP. A confidence criterion was applied to discern the risk of floor water inrush. These results were compared with those from a secondary fuzzy comprehensive evaluation; the results from the present method agrees well with field-observed results. This approach provides a referential methodology for engineers to systematically assess and manage risk of floor water inrush in coal mines.ZusammenfassungEin attributsynthetisches Bewertungssystem wurde mit attributmathematischer Theorie und dem analytischen Hierarchieprozess kombiniert, um das Risiko von Liegendwassereinbrüchen im Kohlenbergbau zu bemessen. Kennziffern für Liegendwassereinbrüche wurden in kontinuierliche Variable, welche quantitativ nach dem Liegendwassereinbruchsrisiko klassiert wurden, und in diskrete Variable unterteilt. Die Letztgenannten wurden nach Expertenbefragung gestaffelt. Funktionen einzelner Indexattributmessungen wurden erstellt, um den Grad der Gruppenzugehörigkeit der Kennziffern kontinuierlicher Variabler zu berechnen. Der Grad der Gruppenzugehörigkeit der Kennziffern diskreter Variabler wurde mittels Techniken der Expertenbefragung evaluiert, wie etwa der Delphimethode. Die Gewichtung des Anteils der Bemessungskennziffern wurde mit dem analytischen Hierarchieprozess rational verteilt. Ein Konfidenzkriterium wurde angewandt, um das Risiko eines Liegendwassereinbruches zu erkennen. Die Ergebnisse wurden mit jenen verglichen, welche mittels sekundärer ganzheitlicher Fuzzy-Bewertung erstellt wurden; die Ergebnisse der vorgestellten Methode stimmt mit Feldbeobachtungen überein. Dieses Vorgehen stellt Ingenieuren eine Referenzmethode zur Verfügung, um das Risiko von Liegendwassereinbrüchen im Kohlenbergbau systematisch einzuschätzen und handzuhaben.ResumenUn sistema de evaluación sintética de atributos se combinó con la teoría matemáticas de atributos y el proceso analítico jerárquico (AHP) para evaluar el riesgo de irrupción de agua desde el piso en minas de carbón. Los índices de evaluación de irrupción de agua fueron divididos en índices variables continuos que fueron graduados cuantitativamente de acuerdo al riesgo de irrupción de agua desde el piso e índices variables discretos, que fueron graduados cualitativamente por opinión experta. Se construyeron funciones de medición de índices de atributos para calcular el grado de pertenencia de los índices variables continuos. El grado de pertenencia de los índices de variable discreta fue evaluado usando técnicas de opinión experta como por ejemplo, el método Delfos. El peso de la contribución de los índices de evaluación, fue racionalmente distribuido por el AHP. Un criterio de confidencia fue aplicado para discernir el riesgo de irrupción de agua. Estos resultados fueron comparados con aquellos obtenidos con una evaluación integral difusa; los resultados del método presentado aquí coinciden bien con los resultados observados en el campo. Esta aproximación proporciona una metodología referencial para ingenieros para relevar y manejar sistemáticamente el riesgo de irrupción de agua desde el suelo en minas de carbón.摘要基于属性数学理论和层次分析方法,提出了一种用于评价煤矿底板突水风险的属性综合评价系统。首先,将底板突水评价指标划分为连续型和离散型两类,连续型变量指标根据底板突水风险进行定量分级,离散型变量指标依据专家意见进行定性分级。其次,通过构建单指标属性测度函数,计算得到连续型变量指标的隶属度,并采用德尔菲法获得离散型变量指标的隶属度。然后,采用层次分析法构造判断矩阵来确定评价指标的权重,应用置信度准则确定底板突水的风险等级。最后,将本方法与二次模糊综合评价法的评价结果作对比分析,本方法评价结果与现场结果具有较好的一致性,为煤矿底板突水风险评估与管理提供了一种有效指导方法。

Predicting geological hazards during tunnel construction

Abstract The complicated geological conditions and geological hazards are challenging problems during tunnel construction, which will cause great losses of life and property. Therefore, reliable prediction of geological defective features, such as faults, karst caves and groundwater, has important practical significances and theoretical values. In this paper, we presented the criteria for detecting typical geological anomalies using the tunnel seismic prediction (TSP) method. The ground penetrating radar (GPR) signal response to water-bearing structures was used for theoretical derivations. And the 3D tomography of the transient electromagnetic method (TEM) was used to develop an equivalent conductance method. Based on the improvement of a single prediction technique, we developed a technical system for reliable prediction of geological defective features by analyzing the advantages and disadvantages of all prediction methods. The procedure of the application of this system was introduced in detail. For prediction, the selection of prediction methods is an important and challenging work. The analytic hierarchy process (AHP) was developed for prediction optimization. We applied the newly developed prediction system to several important projects in China, including Hurongxi highway, Jinping II hydropower station, and Kiaochow Bay subsea tunnel. The case studies show that the geological defective features can be successfully detected with good precision and efficiency, and the prediction system is proved to be an effective means to minimize the risks of geological hazards during tunnel construction.

Mechanical properties of square-steel confined-concrete quantitative pressure-relief arch and its application in a deep mine

Abstract Providing support in deep and complex roadways is one of the major challenges in the mining industry; thus, a square-steel confined-concrete (SQCC) support system has been proposed and an SQCC quantitative pressure-relief arch (SQCC arch) has been developed for roadways in complex environments that are subject to high stress or are affected by faults or mining operations. A self-developed full-size large-scale test system for underground confined-concrete arches has been used to perform indoor comparative tests on a vertical-wall semicircle SQCC arch vs. a U29 arch, which is commonly used in mining. A combination of an indoor test and numerical analyses has shown that the SQCC arch deformation and failure pattern is ‘bulged arch top, retracted arch leg’. The most severe damage position occurs in the area between the middle of the arch leg and the spandrel, and the quantitative pressure-relief device can be used effectively. Compared with the U29 arch’s ‘Z’-shaped bending failure pattern at the arch leg, overall out-of-plane instability and rapid decline in bearing capability, the SQCC arch’s ultimate bearing capability is 2.15 times that of the U29 arch. In addition, the SQCC arch has an excellent bearing capability in the late stage. The SQCC arch support system is implemented in the fault-affected Zhaolou coal mine roadway to reinforce control over the surrounding rock. After 157 d, the maximum deformation at the arch measurement point is 33.1 mm, and the surrounding rock deformation is well controlled.

The control effect of surrounding rock with different combinations of the bolt anchoring lengths and pre-tightening forces in underground engineering

The anchoring length and the pre-tightening force are the two main factors influencing the control effect of surrounding rock in bolt support. To study the influences, a theoretical analysis is made on the stress distribution law of the surrounding rock with different anchoring lengths and pre-tightening forces; a high pre-tightening force quantitative exerting device for high strength bolts is developed with a function of automatic anchor retreat; and four field test plans are designed and carried out with different combinations of bolt anchoring lengths and pre-tightening forces to comparatively analyze their control effect of surrounding rock. The theoretical analysis shows that as the bolt anchoring length is constant, the effective compressive stress area in the surrounding rock of the bolt non-anchoring section increases along with the increase of the pre-tightening force; a certain length of non-anchoring section is helpful to play the bolt support function, but the anchoring length should not be too short. The field test shows that increasing pre-tightening force is an effective way to improve the control effect of surrounding rock; under certain conditions, an appropriate reduction of the bolt anchoring length will not significantly weaken the control effect of surrounding rock. That verifies the theoretical analysis. The study provides some useful guidance for the selection of the parameters of the bolt support in underground engineering.