不同减载措施下高填黄土拱形明洞结构受力研究

高填明洞比常规明洞承受的荷载大、结构更加复杂,减载后的土压力变化是否有利于明洞结构受力尚不明确。文章通过室内模型试验,研究了两种减载措施下沟槽式高填黄土拱形明洞受力特性,得到了明洞周围土压力和外侧应力随填土高度的变化规律及减载效果。试验结果表明,EPS板、EPS板+土工格栅减载可将明洞拱圈上方土压力转移至明洞两侧,使拱顶、拱底土压力减小,两侧土压力增加;明洞外侧各截面应力均减小,铺设减载材料对截面不同位置的外侧应力影响程度依次为拱腰>侧墙>拱顶>拱肩>拱底。采用有限元平面应变模型,对试验过程进行数值模拟分析。结果显示,明洞周围土压力、外侧应力与试验结果平均相对误差分别为11.7%和14.6%;随着填土高度的增加,明洞内力减载量增加,且其变化率增大。因此,实际沟槽式明洞减载工程中,在保证明洞衬砌结构安全情况下,应合理选择减载材料及基础刚度。

Study on the Mechanical Behaviors of High-filled Loess Arched Open Cut Tunnel under Different Load Reduction Measures

Compared with the conventional open cut tunnel,the applied load is larger and the structure is more complex concerning the high-filled open tunnel.It is not clear if the soil pressure change after load reduction is fa⁃vourable for the tunnel structure in terms of mechanical behaviors.A Study on the mechanical behaviors of trench type high-filled arched open cut tunnel in loess under two load reduction measures is conducted through in door model test,and the law of soil pressure and lateral stress varying with fill height around the open cut tunnel and the load reduction effect are obtained.The test results show that the soil pressure above the arch can be transferred to the two sides of open cut tunnel due to the load reduction measures of EPS plate,EPS plate and geogrid,which re⁃duces the soil pressure on the vault and arch bottom and increases the soil pressure on both sides;the stress on each section outside tunnel is reduced,and the orders in terms of effect of the load reduction materialon external stresses at different sections are haunch,side wall,vault,spandrel and arch bottom.A numerical simulation analysis on the test procedure is under taken by FEM strain model,with the results indicate that the average relative errors between the soil pressure,lateral pressure and the test results are 11.7%and 14.6%;load reduction of internal force increas⁃es with an increase of fill height and its change rate increases.For the load reduction of trench type open cut tunnel,it is necessary to reasonably select load reduction material and foundation stiffness under the condition of guarantee⁃ing the safety of lining structure of open cut tunnel.