旧水泥路面沥青加铺改造中弯沉指标研究

Deflection Criterion at the Joint of Existing JPCP Pavement Overlayed with HMA

摘要:

使用有限元方法建立旧水泥混凝土路面模型,采用弹簧单元模拟水泥路面接缝处荷载传递性能,分析了接缝两侧水泥混凝土板的弯沉差和平均弯沉随弹簧单元弹性系数的变化规律.在此基础上,建立水泥路面沥青加铺层模型.计算发现,沥青加铺层底部在原水泥路面接缝处存在剪应力集中现象,进而分析了旧水泥路面接缝处沥青加铺层底部的剪应力随弯沉差的变化规律.根据莫尔库仑强度理论,以沥青加铺层底部的剪应力不大于其容许剪切强度为判断标准,提出旧水泥混凝土路面的弯沉差指标.此指标在旧水泥路面沥青加铺改造时可作为评价接缝传荷能力的参考依据.

Abstract:

When hot mixture asphalt(HMA) is used to remedy functional or structural deficiencies of existing joint plain concrete pavement(JPCP),reflection cracking is a major distress mode in HMA overlay.The basic mechanism of reflection cracking is the propagation of cracks through the overlay due to deflection difference at the joints vicinity of the existing pavements.The model of JPCP was created by three finite element method and the relationship between joint deflection difference and effects such as base modulus,elastic coefficient of spring elements was discussed.Based on the model of JPCP,the finite element model of asphalt overlay was created then and shear stress concentration phenomenon was founded at the bottom of HMA where was just above the joint of JPCP.So,the rule of the shear stress at the bottom of HMA with deflection difference was studied.According to Coulomb strength theory and shear fatigue equation of asphalt concrete,the criterion of deflection difference of existing JPCP was put forward by the method that allowable shear stress was less than ultimate strength.The criterion can provide reference for evaluating the transfer ability of JPCP when the asphalt concrete over JPCP is adopted.