西部钻井法“一钻成井”新型高强复合井壁力学特性

Mechanical properties of a new high-strength composite shaft lining for the “one drilling and forming process” drilling method in western China

  • 摘要: 针对西部地区富水弱胶结地层中深、大钻井井筒“一钻成井”支护难题,提出采用高强钢板−混凝土复合井壁新型结构。首先,以内蒙古鄂尔多斯市陶忽图煤矿北风井为工程原型,基于相似理论推导了复合井壁结构模型试验相似指标,通过正交模型试验,研究了不同井壁厚度、混凝土强度等级和钢板型号情况下高强钢板−混凝土复合井壁的力学特性。其次,采用数值模拟方法,计算分析了高强钢板−混凝土复合井壁极限承载力的影响因素及其变化规律。然后,根据模型试验与数值计算结果,构建了高强钢板−混凝土复合井壁承载力和混凝土抗压强度提高系数计算公式,并给出了各影响因素的取值范围,同时提供了该种井壁结构的工程应用设计优化方法。最后,分析了复合井壁结构中锚卡的力学作用效应。研究结果表明,在复合井壁结构中,由于高强钢板屈服强度高,可更好地对中间混凝土产生复合约束作用,混凝土抗压强度提高系数可达2.3~2.6,井壁承载力显著提高。在相同条件下,与Q345钢板相比,高强钢板(Q460~Q620)−混凝土复合井壁的极限承载力可提高7.14%~19.46%,井壁厚度可减薄8.18%~19.52%,且增大内层钢板厚度更有助于提高井壁极限承载力。复合井壁结构中锚卡约束着内钢板,使其达到屈服应力后不会过早发生屈曲失稳,同时对中间混凝土提供约束作用,保证其处于三向受压状态,2者起到很好的复合作用,有利于井壁结构整体受力。

     

    Abstract: Aiming at the problem of “one drilling and forming process” support for deep and large drilling shafts in water-rich and weakly cemented strata in western China, a new structure of high-strength steel plate-concrete composite shaft lining was proposed. Firstly, based on the similarity theory, the similarity index of the composite shaft lining structure model test was derived using the north ventilation shaft of the Taohutu coal mine in Erdos city, Inner Monglia, as the engineering prototype. The mechanical activation behavior of high-strength steel plate-concrete composite shaft linings was studied by an orthogonal model test with different shaft lining thicknesses, concrete strength grades, and steel plate types. Secondly, the numerical simulation method was used to calculate and analyze the influencing factors and variation rules of the ultimate bearing capacity of the high-strength steel plate-concrete composite shaft lining. Thirdly, based on the results of model tests and numerical calculations, the calculation formulas of the bearing capacity of high-strength steel plate-concrete composite shaft lining and the improvement coefficient of concrete compressive strength were obtained, and the ranges of influencing factors were given, which provides a design optimization method for the engineering application of this kind of shaft lining structure. Finally, the mechanical action effect of the anchor cards in the composite shaft lining structure was analyzed. The results show that in the composite shaft lining structure, due to the high yield strength of high-strength steel plate, it can better produce a composite restraint effect on the intermediate concrete. The compressive strength improvement factor of concrete can reach 2.3−2.6, and the bearing capacity of shaft lining can significantly be improved. Under the same conditions, compared with the Q345 steel plate, the ultimate bearing capacity of high-strength steel plate (Q460−Q620) -concrete composite shaft lining can be increased by about 7.14%−19.46%. And the thickness of the shaft lining can be thinned by 8.18%−19.52%, and increasing the thickness of the inner layer of the steel plate is more helpful to improve the ultimate bearing capacity of the shaft lining. The anchor card in the composite shaft lining structure restrains the inner steel plate so that it does not buckle and destabilize prematurely after reaching the yield stress, and at the same time provides restraint to the intermediate concrete for ensuring that it is in a triaxial compression state. Both of them play a good composite role and contribute to the overall force of the shaft lining structure.

     

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