Rock Mass Pressure Release Rate Analysis for Double-Arch Tunnel

The theory of double-arch tunnel as a new structure form of highway tunnel is still unmatured up to now.According to the similar principle of elastic theory,the three-dimensional model tests simulating the excavation stage of double-arch tunnel were carried out with the background of two double-arch tunnel being constructed in the Yuanmou highway,Yunnan Province.The simple stress state and complex stress condition under oblique pressure were simulated in the test.In present paper,the distribution of stress in the wall rock mass was measured with earth-pressure cell during the tunnel excavation.An innovated 'rock mass pressure release rate' idea was suggested.Using this method the results of the model test were analyzed.The distributions of stress in the wall rock mass of double-arch tunnel are obtained.Some valuable results have guiding significance for the design and construction of the double-arch tunnel.