深基坑内支撑调节对邻近隧道受力特性相互影响规律试验研究

现有基坑近接隧道施工的保护措施多为加强支护刚度或采用轴力伺服系统以减小围护结构变形,未能深入考虑支撑伸缩调控下基坑-隧道的受力特性。为了明确基坑开挖施工对邻近既有隧道影响以及可调节内支撑伸缩对“基坑-隧道”受力特性的影响规律,开展了砂土地基中“基坑-隧道”相互影响的室内模型试验研究。获得了隧道的内力、周围土压力、隧道上部地表沉降、地连墙变形、墙背土压力等变化规律。研究结果表明：深基坑开挖施工过程中,隧道呈现上下压缩、左右拉伸的趋势。临近基坑一侧的土压力减小迅速,远离基坑一侧的土压力表现为增大。周边地表沉降呈碟形。内支撑主动伸缩调控下,基坑下部支撑伸缩引起的隧道弯矩变化量大于调控上部支撑,同时伸缩三道支撑时影响最大。支撑缩短时,隧道拱顶、拱底弯矩值正向增大,拱腰弯矩值反向增大。支撑伸长时,拱顶、拱底弯矩值减小,拱腰弯矩值增大。支撑伸缩对隧道拱腰水平土压力影响明显,对拱顶和拱底竖向土压力影响微弱。

Experimental study on the influence law of adjustable internal support pit support structure on adjacent tunnel

The existing protection measures for the construction of foundation pit near tunnel are mostly to strengthen the support stiffness or adopt axial force servo system to reduce the deformation of the enclosure structure, without considering the force characteristics of foundation pit-tunnel under the regulation of support expansion and contraction. In order to clarify the influence of pit excavation on the adjacent existing tunnel and the influence of adjustable internal support expansion and contraction on the force characteristics of "pit-tunnel", an indoor model study on the interaction of "pit-tunnel" in sandy soil foundation was conducted. The internal force of tunnel, surrounding soil pressure, settlement of tunnel upper surface, deformation of ground connection wall and soil pressure behind the wall were obtained. The results of the study show that during the excavation of the deep foundation pit, the tunnel shows the trend of up and down compression and left and right stretching. The soil pressure on the side near the pit decreases rapidly, and the soil pressure on the side far from the pit shows an increase. The settlement of the surrounding ground surface is in the shape of a disc. Under the regulation of active expansion and contraction of the inner support, the amount of change in tunnel bending moment caused by the expansion and contraction of the lower support of the pit is greater than that of the upper support of the regulation, and the impact is greatest when three supports are expanded at the same time. When the support is shortened, the tunnel arch top and arch bottom bending moment values increase in the forward direction, and the arch waist bending moment values increase in the reverse direction. When the support extension, the arch top and arch bottom bending moment value decreases, and the arch waist bending moment value increases. The influence of support expansion and contraction on the horizontal earth pressure of tunnel arch waist is obvious, and the influence on the vertical earth pressure of arch top and arch bottom is weak.