再论大采高采场顶板“组合短悬臂梁−铰接岩梁”定量化结构

Further discussion on the quantitative structure of “combined short cantilever-articulated rock beam” in roof with large mining height stope

  • 摘要: 针对大采高采场“组合短悬臂梁−铰接岩梁”定量化结构进行研究,采高加大必然引起采场覆岩在横向、纵向的活动范围加大,由于采场覆岩自下而上运动以及冒落碎胀的特点,必将使采空区冒落空间在某一时间趋近于零,因此提出了对采场支架产生作用力的顶板岩层是有范围的,即存在边界层并给出了边界层的概念和判断方法。随着采场的继续推进,采空区冒落的矸石将继续在上覆岩层的作用下发生蠕变而再次压缩变形,从而引起上覆岩层多次下沉传导,引起地表沉陷直至最终稳定,因此从对采场矿压显现有影响的角度将采场至地表的覆岩分为近场岩层和远场岩层。近场岩层为支架上方至边界层内的复合岩层,远场岩层为边界层至地表的复合岩层,近场岩层运动规律是采场矿压研究的重点、远场岩层运动规律是开采地表沉陷研究的重点。基于大采高采场下位复合顶板在垮落前不能触矸而呈“组合短悬臂梁”结构、其上位复合顶板岩层在采场前方煤壁、支架与直接顶联合支撑体、采空区冒落矸石支撑下在采场横向呈“铰接岩梁”结构的特点,提出了大采高采场近场岩层中直接顶、基本顶的新概念并给出了定量化判定方法,从而形成了大采高采场顶板“组合短悬臂梁−铰接岩梁”定量化结构。呈“铰接岩梁”结构的基本顶岩层一般会有一层甚至多层,取决于采高与顶板岩层的厚度、强度、层位等,其形成铰接结构的基本条件是:① 基本顶可能下沉量小于其极限下沉量( \Delta _\mathrmm < \Delta _\mathrmj );② 在结构面的中截面上部应力大于其抗拉强度( \sigma _\mathrmt>R_\mathrmt )且下部应力小于其抗压强度( \sigma _\mathrmc < \leftR_\mathrmc\right );③ 断裂步距大于其厚度的2倍。以曹家滩煤矿10 m超大采高采场为工程背景,通过现场实测分析得到边界层存在的客观性。作为大采高采场“组合短悬臂梁−铰接岩梁”定量化结构理论的应用,研究确定了曹家滩煤矿10 m超大采高采场设备回撤专用垛式支架的支护强度。

     

    Abstract: Quantitative research on the structure of “combined short cantilever-articulated rock beam” in roof with large mining height stope, the increase of mining height will inevitably lead to the increase of the activity range of the overlying strata in the horizontal and vertical directions. According to the characteristics of bottom-up movement and caving expansion of the overlying strata in the stope, the caving space in the goaf will be close to zero at a certain time, it is proposed that the roof strata that product stress on the support are within a certain range, that is, there is a boundary strata in the roof, and the concept and judgment method of the boundary strata are given. With the continuous advancement of the stope, the falling gangue will continue to creep and compress again under the action of the overlying strata, which will cause the overlying strata to sink many times, and cause surface subsidence until it finally stabilizes. Therefore, the overlying strata from the stope to the surface are divided into near-field strata and far-field strata from the perspective of the influence on the ground pressure behavior of the stope, the near-field rock strata refer to the composite rock strata that from the support to the boundary strata, and the far-field rock strata refers to the composite rock strata that from the boundary strata to the surface. The movement law of rock strata in the near-field is the focus of studying the ground pressure of the stope, and the movement law of rock strata in the far-field is the focus of studying the surface subsidence of the stope. Based on the characteristics that the lower composite roof of the large mining height stope cannot touch the gangue before it collapses and presents a “combined short cantilever beam” structure, and the upper composite roof rock strata present an “articulated rock beam” structure in the horizontal direction of the stope under the support of coal wall, the combined support body of support and direct roof, and caving gangue in the goaf, the new concept of immediate roof and main roof in the near-field of large mining height stope is proposed and the quantitative judgment method of immediate roof and main roof is obtained. Therefore, the quantitative structure of “composite short cantilever beam-articulated rock beam” of roof in large mining height stope is formed. The main roof strata that form the “articulated rock beam” structure generally have one or more layers, depending on the mining height and the thickness, strength, and position of the roof strata. The basic conditions for the formation of the articulated structure are:① the possible subsidence of the main roof is less than its limit subsidence ( \Delta _\mathrmm < \Delta _\mathrmj ), ② the stress in the upper part of the middle section of the structural plane is greater than its tensile strength ( \sigma _\mathrmt>R_\mathrmt ), the stress in the lower part of the middle section is less than its compressive strength ( \sigma _\mathrmc < \leftR_\mathrmc\right ), ③ The fracture distance of the rock strata is greater than 2 times of its thickness. Taking the 10 m super large mining height longwall face of Caojiatan Coal Mine as the engineering background, the objectivity of the existence of boundary strata is obtained by the field measurement and analysis, as the application of the quantitative structure theory of “composite short cantilever beam-articulated rock beam” of roof in large mining height stope, the support strength of the special stacking support for the longwall face retracement with the 10 m large mining height was determined.

     

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