Control Technology and Effect Analysis of Surrounding Rock Pressure in Shallow-buried Loess Tunnel
To address the issue of decreased safety performance of support structure in loess tunnels due to uneven loading,this study was based on the measured data from 55 monitoring sections of 27 shallow-buried loess tunnels in China. It elucidated the distribution patterns of surrounding rock pressure in shallow-buried loess tunnels under different geographical zones.By combining numerical calculation numerical and model test,the study revealed the causes of uneven loading in shallow-buried loess tunnels and proposed tunnel load control techniques. Additionally,the effectiveness of these load control techniques was analyzed.The results show that the surrounding rock pressure of shallow-buried loess tunnels is mainly distributed in a butterfly shape,with stress concentration commonly observed at the 60° position of the arch and arch foot.The average value of surrounding rock pressure is 112 kPa,with a median value of 68 kPa.The loads at the arch foot and the 60° position of the arch circle can be up to 1.9-2.2 and 1.6-1.9 times the load of the vault,respectively.When the tunnel is located in the transition from clayey loess area to general loess area and sandy loess area,the butterfly-shaped distribution of surrounding rock pressure becomes increasingly prominent. Uneven settlement of strata,continuous expansion of fracture surfaces,and weaker soil strength at corresponding locations are the main causes of uneven loading in shallow-buried loess tunnels.By applying a load control layer composed of"grouting small conduits+grouting reinforcement layer"at certain positions on the tunnel arch shoulder and arch foot,control of surrounding rock pressure can be achieved. Load control results in a reduction of approximately 20％-30％ in the load on the tunnel arch shoulder and arch foot,the settlement deformation of the soil above the vault decreased by 10％-20％.The tension on the vault is alleviated,and the compression on the arch shoulder and side wall is weakened. The proposed load control technique effectively improves the stress of the support structure and achieves favorable results.
tunnel engineeringload controlmathematical statisticsmodel testnumerical calculationsurrounding rock pressure
万方数据
维普
