抗拔锚杆荷载-位移曲线拟合模型对比

研究抗拔锚杆荷载-位移曲线(P-S曲线)的基本特征,从岩体的性质出发,分析曲线两种类型的发展趋势。基于锚杆P-S曲线的特征,从理论上验证双曲线模型、指数模型、幂函数模型的可行性,并在Pu2处(即极限承载力12处)比较3种模型的优缺点。结合3种模型分别对现场实测数据进行拟合,进一步验证各模型的精确度和适用性。结果表明:幂函数模型拟合精度最高,适用范围广,指数模型次之,双曲线模型相对较差;抗拔锚杆P-S曲线的陡峭程度与幂函数的上凸指数有关,上凸指数介于0.75~1时曲线呈陡峭型。建议根据实际岩体性质判断曲线类型选择合适的数学模型进行描述,描述锚杆P-S曲线时优选幂函数模型。

Contrast analysis on prediction models for load-displacement curve of uplift anchor

We study the basic characteristics of load displacement curve(P-S curve) of uplift anchor in this paper.According to the property of rock mass,we analyze the development trend of two kinds of curves.Based on the basic characteristics of P-S curve of uplift anchor,we verify theoretically the feasibility of hyperbola model,exponent model and power function model,compare the advantages and disadvantages of the three models at Pu/2 position(the half of ultimate bearing capacity),and use the three models to fit the measured data to further verify the accuracy and applicability of each model.The results show that the power function model has the highest precision and wide range of application,while exponent model is moderate in accuracy,and hyperbola model is relatively worse than the aforementioned ones.The steepness of the P-S curve of the uplift anchor is related to the upper convex exponent of the power function,and the curve is steeper when the upper convex index is between 0.75-1.It is suggested that the proper mathematical model shall be selected to describe the curve type according to the actual rock mass properties,and the power function model is preferred when describing the P-S curve of anchor bolt.