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System components and layout
Published in David Butler†, John W. Davies††, Urban Drainage, 2000
David Butler†, John W. Davies††
Fig. 7.2 illustrates how the vertical position of a sewer is defined by its invert level (IL). The invert of a pipe refers to the lowest point on the inside of the pipe. The invert level is the vertical distance of the invert above some fixed level or datum (for example, in the UK, above ordnance datum (AOD)). Other important levels shown in Fig. 7.2 are the soffit level which is the highest point on the inside of the pipe and the crown which is the highest point on the outside of the pipe. Using the nomenclature defined in Fig. 7.2:
Assessment of Excavated Tunnels Stability in the Maya Archeological Area of Copán, Honduras
Published in International Journal of Architectural Heritage, 2023
F. Pires, E. Bilotta, A. Flora, P. B. Lourenço
Before carrying out the stability analyses, the stress distribution around tunnels has been initialized calculating the following steps: (i) a lithostatic stress distribution (K0 condition) is initially assumed; (ii) an initial degree of saturation Sr= 20% is adopted by assigning to the soil material a corresponding apparent cohesion calculated according to Equation (2); (iii) the tunnel opening is simulated by removing the corresponding soil elements; (iv) when applicable (i.e., for T3 sections), the lining is installed; (v) the increase of the degree saturation caused by rain is simulated by reducing the apparent cohesion, cunsat. Different values of apparent cohesion are targeted in step (v), scanning the soil-water characteristic curve in Figure 8. Hence, for each level of apparent cohesion, a stability assessment is carried out according to the strength reduction procedure described in the previous section. For T3 sections the strength reduction procedure was applied only to the ground above the tunnel invert level, since the water infiltration is assumed to take place from above. Consequently, the layer below the tunnel invert was assumed to have a stable cohesion, corresponding to the initial degree of saturation.
Experimental study on deformational resilience of longitudinal joint in shield tunnel lining
Published in Structure and Infrastructure Engineering, 2022
Yanjie Zhang, Yalda Saadat, Hongwei Huang, Dongming Zhang, Bilal M. Ayyub
In this calculation model, the tunnel is assumed to be embedded in the typical Shanghai soft soil. As shown in Figure 5, the red dots represent the position of longitudinal joint at tunnel springline; the buried depth (H) of the tunnel is 15 m; the soil unit weight (γ) is 18 kN/m3; the coefficient of lateral pressure (K0) is 0.65; and the coefficient of ground resistance (Ks) is 6000 kN/m3. According to the joint analytical model, the earth pressures can be calculated as illustrated in Figure 5, where p1 is the vertical overburden soil pressure, p2 is the reaction pressure at the bottom of the lining, p3 is the total lateral earth pressure developed at the crown level of the tunnel lining, p4 is the additional lateral earth pressure developed at the tunnel invert level, p5 is the self-weight of the tunnel lining, p6 is the soil resistance pressure, and ph is the soil resistance developed at the springline of the tunnel.
A horizontal convergence monitoring method based on wireless tilt sensors for shield tunnels with straight joints
Published in Structure and Infrastructure Engineering, 2021
Fei Wang, Jingkang Shi, Hongwei Huang, Dongming Zhang, Dejun Liu
The analytical solution of tunnel deformation employed in this paper is mainly based on the solution proposed by Lee, Hou, Ge, and Tang (2001). The main idea is to equivalent the jointed shield tunnel lining as a continuous ring structure under plane strain condition. An earth pressure distribution pattern is proposed based on the long-term behaviour of shallow tunnels constructed in soft clays. The soil pressure distribution can be illustrated in Figure 1, where p1 is the vertical soil pressure, p2 is the reaction pressure at the bottom, p3 is the total lateral earth pressure developed at the tunnel crown level, p4 is the additional lateral earth pressure developed at the tunnel invert level, p5 is the self-weight of the tunnel lining and p6 is the soil resistance pressure. The joint stiffness is constant and given by the value of stiffness ratio. The force method is used to determine the internal forces and displacements of jointed tunnel lining.