地铁车站修建中面临着所处场地交通繁忙、周边管线密集、车站埋深较大以及施工区间地层地质条件差等问题。洞桩法因其地层适用性强、施工占地面积小以及施工对地层扰动小等特点逐渐成为复杂城市环境下地铁车站施工的首选工法。何家营站作为黄土地区埋深最大车站且首次采用洞桩法施工，车站承载结构的受力机理与施工引起的变形规律不明确，故本文以西安黄土地区地铁何家营站为背景，采用数值模拟、理论分析以及现场监测等手段对车站关键阶段施工引起的地层沉降、结构受力以及导洞围岩压力分布规律进行研究，主要工作及结论如下：

    （1）通过对车站施工全过程进行数值模拟，得到了各关键阶段施工下地层沉降以及支护结构受力规律：导洞施工引起的地层沉降比最大，其次是扣拱施工，车站主体施工完成后，由于站内土体开挖卸载，车站上方地层发生沉降减小的回弹现象。导洞衬砌内力受群洞先后开挖影响严重，后行导洞施工距离先行导洞越近、相邻导洞开挖面积越大，先行洞的结构内力增幅就越大，导洞结构内力最大位置始终在拱脚部位。

    （2）针对导洞施工沉降过大问题，通过优化导洞施工顺序能有效减小导洞施工对地层的扰动，其中“先边后中、先上后下”的导洞顺序施工引起的地层沉降最小。针对某些对沉降控制要求较高的特殊工程，通过减少导洞数量以及导洞总开挖面积，优化车站导洞类型的方案能有效控制洞桩法施工引起的地层最大沉降，其中4导洞型洞桩法控制沉降效果最佳。未支护情况下，导洞土方开挖量与对应地表最大沉降呈线性关系。

    （3）在既有理论基础上，总结了导洞阶段考虑导洞施工顺序下的导洞围岩压力计算公式，分析了导洞埋深、各导洞净距，土体强度以及导洞尺寸等参数变化对各洞围岩压力的影响。从现场监测数据以及围岩压力理论计算结果可以看出，先行洞的围岩压力远大于后行洞，各洞左侧与右侧围岩压力比值远大于1，各洞受偏压荷载显著。

    （4）将本文理论得到的围岩压力值分别与现场实测值和既有理论的围岩压力值进行对比分析，本文理论计算的各洞垂直、侧向围岩压力与既有理论较接近且均大于现场实测值，但本文理论的压力值能更好的反应各洞测点围岩压力的偏压状态。 

Subway station construction is faced with the problems of busy traffic, dense surrounding pipelines, large depth of station and poor geological conditions in the construction section. The pile-beam-arch method has gradually become the preferred method for subway station construction in complex urban environments because of its strong stratum applicability, small construction area and small disturbance to the stratum. Hejiaying station is the deepest station in the loess stratum and is first constructed by pile-beam-arch method. The stress mechanism of the bearing structure of the station and the deformation law caused by the construction are not clear. Therefore, this paper takes the subway Hejiaying station in the loess stratum of Xi’an as the background and uses numerical simulation, theoretical analysis and field monitoring to study the stratum settlement, structural stress and the distribution law of the surrounding rock pressure of the pilot tunnel caused by the construction in the key stage of the station. The main work and conclusions are as follows.

(1) Through the numerical simulation of the whole construction process of the station, the ground settlement and the stress law of the supporting structure under the construction of each key stage are obtained: the ground settlement ratio caused by the guide tunnel construction is the largest, followed by the arch buckle construction. After the completion of the main construction of the station, due to the excavation and unloading of the soil in the station, the ground above the station has a rebound phenomenon of reduced settlement. The lining internal force of the guide tunnel is seriously affected by the excavation of the group tunnels. The closer the construction distance of the rear guide tunnel is to the first guide tunnel, and the larger the excavation area of the adjacent guide tunnel is, the greater the increase of the structural internal force of the first tunnel is, and the maximum position of the structural internal force of the guide tunnel is always at the arch foot.

(2) In view of the excessive settlement of pilot tunnel construction, the disturbance of pilot tunnel construction on the stratum can be effectively reduced by optimizing the construction sequence of the pilot tunnel. Among them, the stratum settlement caused by the construction sequence of ‘first edge and then middle, first upper and then lower’ is the smallest. In view of some special projects with high requirements for settlement control, by reducing the number of guide holes and the total excavation area of guide holes, the scheme of optimizing the type of station guide holes can effectively control the maximum settlement of strata caused by the construction of pile-beam-arch method. Among them, the 4-type tunnel pile method has the best settlement control effect. In the case of no support, the excavation amount of the pilot tunnel has a linear relationship with the corresponding maximum ground settlement.

(3) On the basis of the existing theory, the calculation formula of the surrounding rock pressure of the pilot tunnel considering the construction sequence of the pilot tunnel in the pilot tunnel stage is summarized. The influence of the parameters such as the depth of the pilot tunnel, the spacing of the pilot tunnel, the strength of the soil and the size of the pilot tunnel on the surrounding rock pressure of each tunnel is analyzed. From the field monitoring values and the theoretical calculation values of surrounding rock pressure, it can be seen that the surrounding rock pressure of the first tunnel is much larger than that of the second tunnel, and the ratio of the surrounding rock pressure on the left and right sides of each tunnel is much larger than 1, and each tunnel is obviously indigenous to the bias load.

(4) The surrounding rock pressure values obtained by the theory in this paper are compared with the field measured values and the surrounding rock pressure values of the existing theory. The vertical and lateral surrounding rock pressures of each tunnel calculated by the theory in this paper are close to and greater than the field measured values, but the theoretical pressure values in this paper can better reflect the bias state of the surrounding rock pressure of each tunnel measuring point.

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