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低温和含水率对重塑性煤体抗剪强度影响研究

Study on the influence of low temperature and moisture content on the shear strength of remodeling coal

  • 摘要: 为了研究温度—含水率耦合作用下重塑性煤体抗剪强度的变化规律,保障松软煤层安全高效稳定开采,采用直剪试验分析了重塑性煤体在较低温度(20、0、-10、-20、-30、-40 ℃)、一定含水率(0、0.8%、4%、8%、12%、16%)耦合作用下的抗剪强度特性,并通过数学统计分析了温度与含水率对抗剪强度的影响。研究结果表明:含水率为0时重塑性煤体的黏聚力随着温度的降低呈幂指数增加;温度—含水率耦合作用下重塑性煤体的抗剪强度均与垂向应力成正比,均符合莫尔-库仑准则;在温度为10~20 ℃、含水率为12%~16%时,黏聚力达到最大值322.9 kPa,最小值138.0 kPa出现在温度-40 ℃、含水率4%附近;在-20~-40 ℃温度下,重塑性煤体内摩擦角随含水率的增加逐渐降低至最小值18.25°;当含水率为6%~13%、温度为-20~10 ℃时,内摩擦角达到最大值31.45°,对应抗剪强度达到最大值。温度—含水率耦合作用下,重塑性煤体抗剪强度、内摩擦角与黏聚力均受温度的影响较大。

     

    Abstract: In order to ensure safe, efficient and stable mining of soft coal seam, the direct shear test was conducted to analyze the shear strength characteristics of remodeling coal under the coupling effect from low temperature (20 ℃, 0 ℃, -10 ℃, -20 ℃, -30 ℃, -40 ℃) and moisture (0, 0.8%, 4%, 8%, 12%, 16%).The mathematical statistics was used to discuss the influence mechanism of temperature and moisture on the shear strength.The results show that, when the moisture is 0, the cohesion exponentially increases with the decrease of temperature.The shear strength of remodeling coal is proportional to the vertical stress, thereby conforming to the Mohr-Coulomb criterion.When the temperature increase from 10 ℃ to 20 ℃, the water content increase from 12% to 16%, the cohesion reaches the maximum of 322.9 kPa.The minimum cohesive of 138.0 kPa occurs near the temperature of -40 ℃ and the moisture of 4%.When the temperature ranging from -20 ℃ to -40 ℃, the internal friction angle gradually decreases to the minimum value of 18.25° with the increase of water content.When the moisture content increase from 6% to 13% and the temperature decrease from -20 ℃ to 10 ℃, the internal friction angle reaches the maximum value of 31.45° and the corresponding shear strength reaches the maximum value.Under the coupling effect from temperature and moisture, the shear strength, internal friction angle and cohesion are more affected by the temperature.

     

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