基于熵权-灰关联法的岩质开挖边坡安全评价模型

根据边坡稳定性评价体系, 选取边坡岩体质量评分、边坡开挖方法调整系数、高度修正系数、结构面调整系数、结构面调整值5个评价指标反映边坡的整体稳定性, 并作为安全评价模型的序列变量; 建立了熵权-灰关联安全评价模型, 将目标边坡作为系统特征序列, 12处岩质边坡作为相关因素序列, 评价了京沪高速改扩建工程沿线典型岩质边坡的安全性, 并提出工程建议; 采用FLAC3D仿真软件, 分析了不同阶段机械开挖和不同炮孔处静力爆破条件下边坡的稳定性变化规律, 以验证安全评价模型的准确性。分析结果表明: 边坡稳定性评价指标可较好地反映边坡的稳定性特征; 熵权-灰关联安全评价模型充分发挥了灰关联法在小样本数据分析的优点, 且由熵权法计算的指标权重改善了传统灰关联分析中由专家打分或平均赋权的缺陷, 使评价结果更加客观; 三级边坡和一级边坡的开挖使边坡K593+260~K593+555的安全系数分别降至1.01和1.00, 和上一级边坡相比降幅分别为34.8%、9.1%, 说明缓倾顺层岩质边坡的开挖会使岩层沿结构面滑动, 使边坡失稳; 瞬时动荷载和荷载积累效应控制静力爆破条件下边坡的稳定性, 瞬时动荷载的出现使边坡安全系数下降了7.7%, 荷载积累效应的消散使安全系数平均回升3.6%, 说明爆破对边坡的松动作用明显, 荷载积累的消散使边坡的稳定性提升。 

Safety evaluation model of excavating rock slope based on entropy-grey correlation method

According to slope stability evaluation system, five evaluation indexes, such as slope rock mass quality score, excavation method adjustment coefficient, height correction coefficient, structural surface adjustment coefficient, and structural surface adjustment value, were selected to reflect the overall stability of slope, and serve as the safety evaluation model sequence variables. The entropy weight-gray correlation safety evaluation model was established. Taking the target slopes as the system characteristic sequence and the 12 rock slopes as the correlation factor sequence, the safety of the typical rock slopes along the reconstruction and expansion project of Beijing-Shanghai Expressway was evaluated, and the engineering advices were provided. FLAC3 D simulation software was used to analyze the stability variation laws of the slopes under different stages of mechanical excavation and static blasting at different blastholes, and the accuracy of the safety evaluation model was verified. Analysis result shows that the evaluation indexes of the slope stability can well reflect the slope stability characteristics. The entropy weight-grey correlation safety evaluation model full plays the advantages of grey correlation method in the analysis of small sample data, and the index weights calculated by entropy weight method improve the defect of the traditional grey correlation analysis that the indexes are weighted by experts or average method, making the evaluation result more objective. The third-grade and first-grade slope excavations reduce the safety factor of the slope K593+260~K593+555 to 1.01 and 1.00, respectively, with decreases of 34.8% and 9.1% respectively compared with the upper grade slope. It shows that the excavation of rock slope with gently inclined bedding slope will cause rock layer slide along structural plane and makes the slope become unstable. Transients dynamic load and load accumulation effect control the stability of the slope under static blasting condition. The occurrence of transients dynamic load reduces the slope safety factor by 7.7%, and the dissipation of the load accumulation effect rises the safety factor by 3.6%. It shows that the blasting has obvious loosening effect on the slope, and the dissipation of load accumulation improves the slope stability.