三峡库区周期性饱水-疏干下嵌岩桩承载力弱化模型研究

Study on Weakening Model of Bearing Capacity of Rock-socketed Pile under Periodic Saturated Water and Drainage in Three Gorges Reservoir Area

针对库区饱水-疏干下砂泥岩的性能劣化试验结果差异大,缺乏周期性饱水-疏干下嵌岩桩承载力弱化分析模型的问题。结合大量饱水-疏干作用下的砂泥岩试验数据,分析了饱水-疏干作用下的砂岩、泥岩的强度弱化规律,发现砂泥岩强度均随着饱水-疏干作用呈对数衰减,初始阶段降低幅度明显,后期下降速度减小,且前10次衰减最明显;此外砂泥岩的抗压强度劣化与其初始抗压强度有关,初始抗压强度高的岩石强度劣化速率较慢,但总劣化程度较高。建立了周期性饱水-疏干下砂岩、泥岩的归一化模型,表明不同强度岩石在饱水-疏干作用下具有一致性衰减规律。考虑饱水-疏干作用下岩土的强度弱化作用,结合建立的周期性饱水-疏干作用下砂、泥岩弱化模型,对桩基规范中嵌岩桩承载力计算公式进行调整优化,并建立了嵌岩桩承载力弱化计算模型,为库区在饱水-疏干环境下桩基承载力弱化和寿命预测提供依据。

In view of the problem that there is a large difference in the performance degradation test results of sand and mudstone and the lack of an analytical model for the weakening of bearing capacity of rock-socketed piles under the periodic saturated water and drainage in reservoir area,based on the experimental data of sand and mudstone under the action of saturated water and drainage,the strength weakening law of sand and mudstone under the action of saturated water and drainage is analyzed,and it’s found that the strength of sand and mudstone decreased logarithmically with the action of saturated water and drainage,which is obvious in the initial stage,especially for the first 10 times,and unobvious in the later stage.In addition,the compressive strength deterioration of sand and mudstone is related to its initial compressive strength.The strength deterioration rate of rocks with high initial compressive strength is slower,but the total deterioration degree is higher.A normalized model of sand and mudstone with periodic saturated water and drainage is established,which indicates that rock with different strength has consistent attenuation law under the action of saturated water and drainage.Considering the weakening of rock and soil strength under the action of saturated water and drainage,and combining the established weakening model of sand and mudstone under the action of periodic saturation and drainage,the calculation formula for the bearing capacity of rock-socketed pile in the pile foundation is adjusted and optimized,and a model for calculating the weakening of rock-socketed pile bearing capacity is established,which provide a theoretical basis for weakening and durability prediction of the bearing capacity of rock-socketed pile foundation in the Three Gorges reservoir area.