套筒刚度对左旋锚杆锚固力的影响研究

The influence of sleeve stiffness on anchoring force of left spiral bolt

实验室短拉拔试验是锚固力学机理分析与锚杆支护技术研究的重要试验手段之一。为了研究套筒径向刚度与锚杆锚固力的关系,分别使用内径皆为30 mm、壁厚31 mm的PVC套筒、壁厚5.8 mm的铝套筒、壁厚5.5 mm和7.0 mm的钢套筒,对肋间距12 mm和48 mm的矿用左旋螺纹钢锚杆进行实验室套筒拉拔试验,得到肋间距12mm和48mm的左旋锚杆在不同套筒(围岩)径向刚度下的拉拔曲线与锚固力数据。研究表明:1)通过厚壁理论计算,建立了实验室内PVC、6061铝和20钢共3种不同材料及适当壁厚的套筒与现场不同围岩刚度对应的仿真方法;2)通过对锚固力与套筒(围岩)径向刚度数据拟合,得到锚固力与不同巷道围岩刚度的类比关系公式,并采用此公式对其他围岩性质下的锚固力进行了计算;3)对于同一肋间距的锚杆,随着套筒径向刚度增加,锚固力不断增大至理论最大值,且套筒(围岩)径向刚度为0时的锚固力值与锚固剂力学参数有关,与围岩性质等因素无关;4)在弹性阶段内,对于锚固于同一刚度套筒的试件,其肋间距越大,锚固力越大。本次试验结果为现场不同煤矿条件的应用提供了理论依据,对现场锚固力的测试具有借鉴意义。

The short encapsulation pullout test(SEPT) is an important experimental method for exploring anchorage mechanics and developing bolt reinforcement technology in the laboratory. In order to study the relationship between the radial stiffness of the sleeve and the bolt reinforcement, the sleeves with 30 mm in inner diameter matching with different materials and wall thicknesses(PVC, 31 mm;aluminum, 5.8 mm;steel, 5.5 and 7.0 mm) have been used. The pullout tests have been conducted on left spiral bolt with rib spacing of 12 mm and 48 mm, and the load-displacement curves and anchoring force data of the two kinds of bolts under different sleeve(surrounding rock) radial stiffness have been obtained. The results have shown that:1) The simulation method between three different materials sleeves(PVC, 6061 aluminum and 20 steel) with appropriate wall thickness in the laboratory and different stiffness of surrounding rock on site has been established via the theoretical calculation of wall thickness;2) The formula of the analogy relationship between anchoring force and surrounding rock stiffness has been established by fitting the anchoring force and sleeve(surrounding rock) radial stiffness of different roadways, and the formula has been applied to calculate the anchoring force under other surrounding rock properties on site;3) For the bolt with the same rib spacing, with the increase of the radial stiffness of the sleeve, the anchoring force gradually increases to a theoretical maximum value, and the anchoring force will be related to the mechanical parameters of the anchoring agent and irrelated to the surrounding rock properties, when the sleeve(surrounding rock) radial stiffness is zero;4) In the elastic stage, for the specimens anchored with the same stiffness sleeve, the larger the rib spacing, the greater the anchoring force. The experimental results provide a theoretical basis for the application of different coal mine conditions, and have a reference for the testing of anchoring force on-site.