CALCULATION METHOD FOR SURROUNDING ROCK PRESSURE OF DEEPLY BURIED TRIPLE-ARCH TUNNEL

Based on the Platts pressure arch theory and process load design method, considering the combined arch effect of the continuous arch tunnel, considering the construction process and the supporting role of the middle partition wall, quantifying the construction disturbance between the adjacent simplified guide holes, and proposing the load distribution model under different construction sections and processes of the deep buried three-arch tunnel, and then improving the calculation method of the surrounding rock pressure of the deep-buried three-arch tunnel, combined with the three-arch tunnel project of Badaling Great Wall station, the theoretical results are compared with the measured data to verify the rationality of the calculation method. Finally, the systematic analysis of the construction process, the width of the diaphragm wall, the span of excavation and other factors on the influence of the surrounding rock pressure law. The results show that: the influence of construction disturbance among deeply buried triple-arch tunnels cannot be ignored, and the excavation of secondary and posterior caverns will expand the loose and broken surrounding rock area above the first cavern causing a more obvious bias pressure phenomenon; when the compressive strength of the rock body of the diaphragm wall is small, it is difficult to improve the surrounding rock pressure distribution by increasing the width of the diaphragm wall. While the compressive strength of the rock body of the diaphragm wall is large, increasing the width can significantly reduce the surrounding rock pressure; the poorer the rock condition, the greater the rock pressure in each chamber of the triple-arch tunnel, and the more obvious the bias pressure phenomenon. Based on the calculation method obtained by Platts pressure arch theory and process load design method, this paper adds the construction influence between adjacent caverns of the continuous arch tunnel, reveals the bias effect of the three-arch tunnel, fills the research gap on the calculation method of surrounding rock pressure of the three-arch tunnel, and provides important reference and guiding significance for the related engineering design.