中文摘要：

城市地下工程建设中，交错重叠隧道施工对地层的多次扰动通常无法避免，对周围环境产生一系列负面影响，对于地铁隧道穿越北京市老城区，此类问题更加突出。依托北京地铁6号线北海北至南锣鼓巷区间隧道工程，该工程为北京地区首例暗挖交错重叠隧道工程，采用数值模拟和现场实测相结合的方法，对5种典型断面在不同开挖顺序、不同空间位置关系、不同超前深孔注浆厚度下的地表变形特性进行研究，取得以下认识：（1）“先下后上”施工方式引起的地表最大沉降值及沉降槽宽度都比“先上后下”施工方式小，更有利于隧道的整体稳定性。（2）随着双线隧道角度的增大，双线隧道逐渐接近，地表变形显著增大。当双线隧道角度大于60＆#176;时，地表最大沉降值超过30 mm的控制标准，需要采取深孔注浆的方式对地层进行预加固。（3）随着注浆厚度的加大，地表和隧道拱顶最大沉降值逐渐减小。综合考虑经济效益和过大注浆压力的不利影响，建议注浆厚度定为1.5～2.0 m。（4）实际监测数据显示采取超前深孔注浆后地表沉降满足控制标准，表明超前深孔注浆加固方式可以有效减少双线隧道开挖引起的地表沉降和沉降槽宽度，降低隧道开挖对周围环境的影响。研究成果可为今后北京同类工程提供参考。

英文摘要：

Construction of crossing tunnels underground in urban area inevitably disturbs the surrounding ground, posing a series of problems on the environment,especially for the old Beijing city. In the construction of Subway Line 6 in Beijing,two tunnels cross each other one over the other in the section between Beihai north to Luoguxiang south,which is a first case of underground tunnel crossing in Beijing. Numerical simulation and field measurement were adopted to study the surface deformation characteristics of five typical sections under different excavation sequences,layouts and grouting methods. The maximum ground surface settlement and the width of settlement trough were smaller and the tunnels were more stable in the case of the lower tunnel excavated first than the ones the upper tunnel excavated first. The surface deformation was found to increase notably with the increase of the crossing angle of two tunnels. When the crossing angle was greater than 60 degrees,the maximum value of ground surface settlement exceeded 30 mm which was above the control standard. The stratum needed to be strengthened through grouting in this case. The maximum settlements at ground surface and tunnel crown decreased with the increase of the thickness of grouted layers. Having considered the economic costs and the unfavorable effects of grouting pressure,the thickness of grouted layers was suggested to be 1.5–2.0 m. The monitored field data showed that the ground surface settlements after grouting met the requirement of control standards and the grouting was an effective method to reduce the ground surface settlement and the width of settlement trough.