考虑土体刚度衰减的地面堆载对既有隧道影响

地面临时堆载可能会使周围土体产生明显的沉降变形,进而对城市地下空间中的邻近既有隧道产生不利影响。理论解析法是评估地表超载对既有隧道影响的有效方法。目前的理论解析分析方法一般假定土体刚度沿既有隧道轴线方向为一定值,忽略了地面堆载引发的土体刚度衰减的影响。基于两阶段分析法提出了考虑纵向土体刚度衰减的地面堆载引发既有隧道变形计算模型。既有隧道被假定为搁置在Winkler地基上的Euler-Bernoulli梁。利用邓肯-张模型对地表堆载引发的土体非线性响应进行评估,并结合现场实测数据对模型的适用性进行验证。研究成果可为合理评估地表堆载对既有隧道的影响提供依据。

Effects of Surface Surcharge on Existing Tunnel Considering Soil Stiffness Degradation

Surface surcharge may induce obvious ground settlements and lead to harmful impacts on the adjacent existing tunnels in the urban underground space. The analytical method is an ecient way to evaluate the effect of surface surcharge on the existing tunnels. Current analytical methods for calculating tunnel settlements due to surface surcharge generally simplified the soil stiffness along the existing tunnel is a constant. The effect of the soil stiffness degradation owing to the surcharge was neglected. This paper presents a two-stage analytical method, which considers the longitudinal degradation of the soil stiffness to study the tunnel mechanical responses to the surface surcharge. The tunnel is simulated as a Euler-Bernoulli beam lying on a Winkler foundation. The Duncan-Chang model is used to evaluate the soil stiffness nonlinearity caused by the surface surcharge. The measurement data from a case study is used to validate the proposed method. The proposed method can provide a reference for estimating the effect of surface surcharge on the existing tunnel reasonably.