充气锚杆极限承载力计算方法

为研究充气锚杆极限承载力计算方法，在模型试验基础上，探讨充气锚杆抗拔过程中的受力特征与破坏形式，分析锚杆荷载-位移曲线变化特征。基于圆孔扩张理论，通过简化力学模型，推导充气锚杆侧阻力与端阻力计算公式，将理论公式计算值与试验成果进行比较。研究结果表明：(1) 采用球孔扩张理论可以较好地描述膨胀体端部对土体产生的弹性、塑性变形力学机制，估算端阻力值。充气膨胀压力对土体的挤压膨胀作用大大增加了锚杆的侧阻力。(2) 极限承载力理论公式计算值与抗拔试验值基本吻合，验证了极限承载理论计算公式的正确性。(3) 通过与螺旋锚杆相比，充气锚杆的承载力约为单锚片螺旋锚杆的4.3倍，约为双锚片螺旋锚杆的1.9倍，充气锚杆的承载能力优势明显。

Calculation method for ultimate bearing capacity of inflatable anchor

In order to explore the calculation method of the inflatable anchor bearing capacity, according to the model test, the stress characteristics and failure forms of the inflatable anchor during pullout are analyzed as well as the variational characteristic of the load displacement curve of anchor. Based on the theory of cavity expansion, the formula for the inflatable anchor side resistance and end resistance calculation are derived through a simplified mechanical model. The calculation values by the theoretical formula are compared with the experimental results. The results of the study show that: (1) the elastoplastic deformation mechanism of the expansion body end to soil can be well described by the spherical cavity expansion theory, as well as the estimation of end resistance value. Due to the inflated pressure on the soil extrusion expansion effect, the anchor side resistance is greatly increased. (2) The results from the ultimate bearing capacity theory formula are coincident with those from the pullout test, so as to validate the ultimate bearing capacity theory formula. (3) With a case of comparison to screw anchor, inflatable anchor shows the 4.3 times of the bearing capacity over single anchor sheet screw anchor and about 1.9 times over double anchor plate screw anchor, so as to show the obvious advantages of the inflatable anchor bearing capacity.