基于围岩松动圈的地下工程参数场位移反分析

 受爆破松动影响，地下洞室开挖后围岩强度会有所降低，根据松动损伤程度将其视为一个连续的三维“参数场”。由围岩松动圈的形成机制，分析地下洞室开挖后松动圈的计算方法，提出考虑松动圈的围岩参数场增量位移反分析法。针对岩土工程反分析计算量巨大的实际问题，对反演计算过程进行了基于MPI的主从式并行框架改进，运用计算机集群网络进行并行计算，减少了迭代计算次数和计算耗时，极大地提高了计算效率。通过对溪洛渡水电站右岸地下厂房的参数反演，得到了较好的反演效果，验证了此法的可行性和合理性。依据反演得到的参数场对现有支护设计及洞室围岩稳定状态进行评价，并对后续开挖进行预测，为工程设计施工提出合理建议，为地下工程参数反演提供了一种新方法和新思路。

DISPLACEMENT BACK ANALYSIS OF PARAMETER FIELD IN UNDERGROUND ENGINEERING BASED ON EXCAVATION DAMAGED ZONE OF SURROUNDING ROCK

Due to excavation blasting，the surrounding rock of underground caverns is loosened and its strength lowers. A continuous three-dimensional data field of surrounding rock parameters is employed to describe the different damage degrees of surrounding rock. According to the formation mechanism of excavation damaged zone(EDZ) of surrounding rock，the method to calculate the EDZ induced by excavation blasting in underground caverns is analyzed. By taking the range of EDZ into consideration，a back analysis method based on incremental displacements is put forward. By employing this method，the fields of surrounding rock parameters can be back analyzed. As back analysis of geotechnical engineering involves enormous amounts of computation，the back analysis process is improved by introducing message passing interface(MPI)-based master-slave parallel framework. The parallel computation can be conducted using computer cluster networks，thus considerably reduce the cost and enhance the efficiency of computation. The proposed method is further illustrated with its application to the large-scale underground caverns of Xiluodu hydropower station. The back analysis results are favorable and the reliability and rationality of the proposed method are proven. Based on the surrounding rock parameters field obtained by back analysis，the current anchor support scheme and the stability of the underground cavern are assessed. Also，the stability condition in subsequent excavation is predicted；and the rational recommendations are made for the engineering design and construction，providing the parameters back analysis of underground engineering with a new method.