富水砂层水平旋喷拱棚力学特性模型试验研究

Model Test on Mechanical Characteristics of Horizontal Jet Grouting Arch Shed in Water-Rich Sandy Stratum

为探究富水砂层中水平旋喷拱棚受隧道开挖及地下水影响的力学特性,对3组不同桩心距的水平旋喷拱棚,分别开展不同开挖进尺及地下水位工况下的模型试验,分析地表沉降,拱棚的挠度、弯矩、轴力及拱棚-地层接触压力的变化规律。结果表明:1)桩心距较小时,地表沉降、桩体纵向轴力及弯矩、周围地层及桩体自身受力变形受隧道开挖及水位工况影响程度降低,但桩体纵向受压区域增大;2)随着桩间咬合厚度的增加,地层受影响区域沿隧道开挖方向前移,当桩心距小于350 mm时(即桩间咬合厚度继续增大),在水平旋喷拱棚的支护下,地层沿隧道开挖方向受扰动区域将不再变化;3)地下水的存在对拱棚的纵向挠度有较大的影响,在富水砂层中,增加桩间咬合厚度即减小桩心距可有效减小开挖面附近的拱棚挠度。

To investigate the mechanical characteristics of horizontal jet grouting arch shed in water-rich sandy stratum affected by tunnel excavation and groundwater,model tests are carried out for three groups of horizontal jet grouting arch sheds with various pile center distances under various excavation footage and groundwater level conditions,and the variation laws of surface settlement,deflection,bending moment,axial force of arch shed,and contact pressure between arch shed and stratum are examined.The results show the following:(1)When the pile center distance is small,the ground settlement,longitudinal axial force and bending moment of the pile,deformation of surrounding strata and the pile are less affected by the tunnel excavation and water level conditions,but the longitudinal compression area of the pile increases.(2)With the increase of the bite thickness between piles,the affected area of the stratum moves forward along the tunnel excavation direction;when the pile center distance is less than 350 mm(that is,the bite thickness between piles continues to increase),the disturbed area of the stratum along the tunnel excavation direction will not change under the support of the horizontal jet grouting arch shed.(3)The groundwater has a great impact on the longitudinal deflection of the arch shed;in the water-rich sandy stratum,increasing the bite thickness between piles(that is,reducing the pile center distance)can effectively reduce the deflection of the arch shed near the excavation surface.