自膨胀锚杆锚固体膨胀剂极限掺量确定方法研究

首次提出了针对大掺量膨胀剂自膨胀锚杆的理论技术基本原理，并阐明其经济效益与极限抗拔力提升效果。但还存在过量膨胀剂会导致自膨胀锚固体撑裂围岩等问题，必须通过确定膨胀剂的极限掺量来解决。因此，提出了应用自膨胀锚杆的两个前提条件，明确了两个层次的试验目的并以此展开试验研究：（1）膨胀致裂法。先进行围岩胀裂破坏试验，获取界面正应力的变化规律和围岩破坏规律，阐释了自膨胀锚固体作用下中风化泥质粉砂岩的开裂破坏演化规律。建立不同位置径向自膨胀应力计算模型，基于接触面上的径向膨胀应力得到了锚固体的膨胀剂临界掺量预测模型，并预测中风化泥质粉砂岩的膨胀剂临界掺量为28.98%。（2）弹性解析法。基于无限大介质中圆孔均匀受压和圆孔的孔边应力集中问题建立了自膨胀锚固体作用下围岩的胀裂破坏模型，得到了一套围岩受自膨胀锚固体作用时的应力分布预测公式，进一步推导出了围岩受径向膨胀应力作用下的临界开裂方程。为降低现场测试的周期和费用，建立了基于声波?回弹值的中风化泥质粉砂岩抗拉强度预测公式。最终，完成了临界开裂方程在基于围岩不完整性和围岩浸水软化影响下的参数修正，并结合了临界掺量值引入了安全储备系数，建立了自膨胀锚固体的膨胀剂极限掺量设计公式，计算出针对中风化泥质粉砂岩的自膨胀锚杆锚固体膨胀剂极限掺量为26.5%。该研究能为自膨胀锚杆在岩土、矿山、水利等领域的推广运用提供技术支撑。

Study on the method for determining the limit content of expansion agent in anchor body of self-expanding bolt

The theoretical and technical principles of self-expanding bolt with large amounts of expansion agents were first proposed, and its economic benefits and the effect of improving the ultimate pullout resistance were addressed. However, excessive expansion agent would generate cracks in the surrounding rock caused self-expanding bolt, and it is highly important to determine the limit content of the expansion agent. Therefore, two prerequisites for the application of self-expanding bolt were proposed, and experimental study were performed based on the clarification of experimental purposes from two levels. The former one is expansion cracking method. Firstly, the bursting and cracking test of surrounding rock was carried out to obtain the change law of normal stress at the interface and the failure law of surrounding rock. The evolution law of the cracking and failure of the moderately weathered argillaceous siltstone under the action of self-expanding anchor body was also explained. A calculation models of radial self-expansion stress at different positions were established. Based on the radial expansion stress of the contact surface, a prediction model of the critical content of the expansion agent of the anchor body was obtained, and the critical content of the expansion agent of the moderately weathered argillaceous siltstone was predicted to be 28.98%. The latter one is elastic analysis method. Based on the problem of uniform compression of circular holes in the infinite medium and stress concentration at the edges of the holes, a model for the expansion and failure of surrounding rocks under the action of self-expanding anchors body was established. A set of formulas for predicting the stress distribution of surrounding rock under the action of self-expanding anchors body was obtained, and a critical cracking equation for surrounding rock under radial expansion stress was derived. In order to reduce the field test cycle and cost, a formula for predicting the tensile strength of the moderately weathered argillaceous siltstone was established based on the acoustic-rebound value. Finally, the parameter correction of the critical cracking equation is completed based on the incompleteness of the surrounding rock and the softening effect of the surrounding rock soaking. Combined with the critical admixture value, the safety reserve coefficient was introduced, and the design formula for the limit content of self-expanding anchor body was established. According to the design formula, it is calculated that the limit content of the self-expanding anchor solid expansion agent for moderately weathered muddy siltstone is 26.5%. The paper can provide technical support for the application of self-expanding bolt in geotechnical, mining and water conservancy fields.