| With the rapid development of traffic network construction in southwest China,a large number of tunnel projects appear in the process of highway construction.Due to a series of problems such as poor geological conditions and complex spatial structure and morphology of tunnel and slope in the tunnel entrance and exit section,the excavation of tunnel entrance section is easy to cause landslides,which seriously affects the safety of project construction.Based on the banqiu tunnel mouth landslide of hebai expressway in guangxi,this paper studies the stability of the bedding slope at the entrance of the shallow buried and biased tunnel,aiming at the problem that the slope in the entrance and exit section of the tunnel project affects the construction safety.The main research work and results are as follows:1.By referring to a large number of literature and engineering examples,the research status of stability of tunnel opening slope at home and abroad was summarized;2.On the basis of collecting and analyzing engineering geological data and site monitoring data of banqiu tunnel,the occurrence process of banqiu tunnel landslide is introduced in detail;3.Using finite difference software FLAC3D analysis class high stress and displacement after tunnel excavation and slope stability,in combination with field investigation,surmed up the class high tunnel landslide genesis:tunnel imports relatively flat terrain,slope of about 20～24°,the terrain effect on tunnel bias is small.But there is a group of 30 O slope to the steep slope weak level,the geological structure of tunnel surrounding rock caused by bias effect obviously,under the effect of bias,the tunnel after excavation,the tunnel surrounding rock stress,displacement,a significant change in tunnel arch foot appear larger concentrated stress,the tunnel surrounding rock on the right side of the arch foot along the slope slip deformation to the weeik level.At the same time,the stress of the rock mass above the tunnel is relaxed,and the shear strength is reduced.As the rock mass on the bias side slides,the arch roof produces shear failure along the plane,and the displacement change law is consistent with the bias direction.At the same time,due to the shallow buried depth of the tunnel,the surface tensile stress of the slope increases greatly after the tunnel excavation,and the slope is prone to form tensile cracks.Under rainfall conditions,the infiltration of rainwater along the slope surface deformation crack aggravates the slope,softens the soft surface,and accelerates the slope sliding.4.For the study of slope ratio and the tunnel buried depth and inner factors such as strata dip Angle influence slope stability of the tunnel,the numerical simulation method,through the analysis of different slope rate,tunnel buried depth and rock strata dip Angle,the tunnel after excavation and surrounding rock stress,displacement and stability coefficient of slope body characteristics,internal factors of the slope stability of tunnel is studied.The results show that:1)with the tunnel excavation,stress relaxation and stress concentration occur in the interior of the slope,and the stability decreases significantly.2)with the increase of the slope rate,the stress inside the tunnel surface increases,the stress in the stress concentration area increases more obviously,the slope displacement also shows an increasing trend,and the stability decreases.3)as the buried depth of the tunnel increases,the surrounding rock stress and displacement of the tunnel increase obviously,but the stress and displacement near the slope decrease and the stability increases,indicating that the influence of the tunnel exeavation on the slope decreases as the buried depth of the tunnel increases.4)The slope stability of the timnel is related to the relationship between the slope Angle and the rock slope Angle.When the rock slope Angle i5 greater than the slope Angle,the slope stability increases with the decrease of the rock slope Angle;when the rock slope Angle is less than or equal to the slope Angle,the slope stability no longer ehanges with the decrease of the rock slope Angle.Figure[43]table[1]reference[57]... |
