锚杆端部形态对锚固居中度影响分析及优化试验研究

Analysis and optimization experimental study on the influence of bolt end shape on eccentricity

  • 摘要: 锚杆支护以其独特的优越性被广泛应用于地下工程建设支护当中,随着工程深度的增加以及地质条件的复杂多变对锚杆锚固性能提出了更高要求,锚杆锚固偏心现象普遍存在于岩土及地下支护工程中,对锚固系统工作性能存在一定的不利影响。采用理论分析、数值模拟和实验室试验等方法,初步研究了螺纹钢锚杆不同端部形态对锚杆居中度的影响机制,明晰了锚杆偏心对锚固性能的影响特征,基于自主设计的不同端部形态锚杆,对锚杆锚固偏心问题的控制对策进行了有效探索。理论分析表明:锚杆端部形态对锚固居中度的影响较大。锚杆锥形尖端容易刺破锚固剂封袋,在钻进搅拌锚固剂时减小了锚固过程中的阻力,同时端部凸出齿轮部分能够固定锚杆钻进搅拌锚固剂过程中相对锚固孔的位置,提高锚杆居中度。数值模拟分析发现,在光滑和粗糙锚固孔条件下,齿轮形和伞齿形端部锚杆相较于原型和锥形端部锚杆的运动轨迹更接近锚固孔中心位置,居中率提高约85%。由试验可知,水平锚固时锚杆偏心程度要高于竖直锚固时,而齿轮形和伞齿形端部在锚固过程中能够限制锚杆的运动轨迹,锚杆基本不会出现偏心现象,且锚固终态时锚杆居中效果较好,其居中度相较于原型端部分别提升81.9%、86.7%左右,锚固力分别提升了16.7%、22.1%左右;锥形端部锚杆居中度相较于原型端部锚杆提升8.4%左右,锚固力提升7.9%左右。研究成果对于提高锚杆锚固居中度、改善锚固性能具有一定的理论与工程应用价值。

     

    Abstract: The bolt support is widely used in underground engineering construction due to its unique advantages. With the increase in engineering depth and the complex and variable geological conditions, higher requirements are being placed on the anchoring performance of bolts. The phenomenon of bolt eccentricity is common in rock and soil and underground support engineering, and it has a certain adverse effect on the working performance of the anchoring system. In this study, theoretical analysis, numerical simulation, and laboratory experiments were used to preliminarily investigate the influence mechanism of different end shapes of threaded steel bolts on the centering degree of the bolts. The aim was to clarify the impact characteristics of bolt eccentricity on anchoring performance and explore effective control strategies for bolt anchoring eccentricity based on independently designed bolts with different end shapes. The theoretical analysis revealed that the end shape of the bolt has a significant impact on its eccentricity. The conical tip of the bolt can easily penetrate the resin grout's sealing bag, reducing the resistance during the anchoring process when drilling and mixing the resin grout. Additionally, the protruding gear portion at the end can fix the position of the bolt relative to the borehole during the drilling and mixing process, thereby improving the eccentricity of the bolt. Numerical simulation analysis found that under smooth and rough borehole conditions, the bolts with gear-shaped and umbrella-shaped ends had motion trajectories closer to the center of the borehole compared to the prototype and conical-shaped bolts, resulting in an approximately 85% increase in centring rate. Experimental results showed that the eccentricity of the bolt during horizontal anchoring was higher than that during vertical anchoring. However, anchor bolts with gear-shaped and umbrella-shaped ends could restrict the motion trajectory of the bolt during the anchoring process, effectively preventing eccentricity. Moreover, these end shapes exhibited better eccentricity in the final anchoring state, with eccentricity approximately 81.9% and 86.7% higher than the prototype, and anchoring forces approximately 16.7% and 22.1% higher, respectively. The conical-shaped end resulted in a centring degree approximately 8.4% higher than the prototype and an anchoring force approximately 7.9% higher. The research results have certain theoretical and engineering application value for improving the centring effects and improving the anchoring performance.

     

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