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钻孔密封段异质结构变形破坏特征试验研究

Experimental study on deformation and failure characteristics of heterostructure in borehole sealing section

  • 摘要: 瓦斯抽采钻孔密封段是由煤-水泥-抽采管组成的异质结构体,为了研究钻孔密封段煤-水泥异质结构的变形破坏特征,采用Vallen AMSY-6 声发射信号采集系统和TAW-2000高温岩石三轴伺服试验机相结合的方法,对煤单体、水泥单体及煤-水泥组合试件进行了单轴载荷作用下的变形破坏全过程声发射试验。
    试验结果表明:煤-水泥组合试件的峰值应力介于煤单体试件和水泥单体试件之间,煤单体试件的强度是水泥单体试件强度的2.1倍;煤-水泥组合试件及煤单体试件的体应变突降点后伴随着声发射振铃计数的激增,而水泥单体试件的声发射指标增长较为平缓,且不同试件都在应力峰值处声发射指标达到最大值,煤-水泥组合试件的振铃计数峰值约为水泥单体试件振铃计数峰值的112倍;
    煤-水泥组合试件及煤单体试件的应力应变曲线表现出峰后的脆性变形特征,而水泥单体试件的应力应变曲线则表现出峰后的塑性变形特征,煤-水泥组合试件的破坏形态为剪切破坏,煤单体试件的破坏形态为“X”状共轭剪切破坏和拉伸破坏,水泥单体试件的破坏形态为拉伸破坏。现阶段我国煤矿瓦斯抽采钻孔封孔材料大多选取水泥基封孔材料,钻孔密封段煤-水泥异质结构的强度同时受到煤体和水泥材料性质的影响;井下水泥基封孔材料选取时,可优先选取凝固后与煤岩体强度差异较小的水泥基封孔材料。

     

    Abstract: Gas drainage borehole sealing section is a heterostructure composed of coal-cement-extraction pipes. In order to study the deformation and failure characteristics of the coal-cement heterostructure in borehole sealing section, the combination of Vallen AMSY-6 acoustic emission signal acquisition system and TAW-2000 high temperature rock triaxial servo testing machine were used to conduct acoustic emission tests of deformation and failure of coal monomer, cement monomer and coal-cement composite specimen under uniaxial load. The test results show that the peak stress of the coal-cement composite specimen is between the coal monomer specimen and the cement monomer specimen, and the strength of the coal monomer specimen is 2.1 times that of the cement monomer specimens. The coal-cement strain composite specimen and the body strain drop point of the coal monomer specimens are accompanied by a sharp increase in the ringing count of acoustic emission, while the acoustic emission index of the cement monomer specimen increases more gently, and the different specimens are at the peak stress. The acoustic emission index reaches the maximum value, and the peak ringing count of the coal-cement composite specimen is about 112 times of the cement monomer test piece; the stress-strain curves of the coal-cement combination test piece and the coal monomer test piece show brittle deformation characteristics after the peak, while the stress-strain curve of the cement monomer specimens show plastic deformation characteristics after the peak. The failure mode of the coal-cement heterostructure specimen is shear failure, and the failure mode of the coal monomer specimen is "X"-shaped conjugate shear failure and tensile failure. The failure mode of the cement monomer specimen is tensile failure. At present, most of the hole sealing materials for coal mine gas drainage in China are cement-based sealing materials. The strength of the coal-cement heterogeneous structure in the borehole sealing section is affected by both the properties of coal body and cement materials. In the selection of underground cement-based sealing materials, the cement-based sealing materials with a small difference in strength from coal and rock after solidification can be selected preferentially.

     

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