Abstract
The intention of this research is to perform structural evaluation on masonry sanitary sewer pipes impacted by tunnel excavation. Until about 1900, it was common to use several layers of brick to construct municipal sanitary sewer lines, and currently thousands of miles of brick sewer lines are still in service. The construction of new underground facilities inevitably disturbs the soil above and will have an impact on the existing masonry sanitary sewer pipes within the zone of influence of the excavation. Masonry pipes are typically susceptible to the longitudinal interaction failure mechanism at the hogging zone of the settlement trough due to their low tensile capacity. In this research standard egg-shaped section for brick sewer were subjected to ground settlements obtained using Attewell method. The greenfield condition is assumed to be applicable with homogeneous ground conditions. The impact of the depth to the tunnel axis and trough width parameter on the settlement trough and associated strains developed in the pipes are subjected to investigation. Tensile strain developed due to axial strain and bending moment are calculated for five different section sizes. Mitigation measures and recommendations are provided
Highlights
Until about 1900, Large sewers were generally constructed of brick
Vorster proposes five soilstructure interaction mechanisms for pipeline failure[8]. These failure mechanisms are: (Mechanism 1): Global Greenfield soil settlement; (Mechanism 2): Gap formation below the pipe; (Mechanism 3): Positive downdrag failure the pipe settles more than the soil; (Mechanism 4): Negative downdrag failure - the soil settles more than the pipe; (Mechanism 5): Longitudinal interaction
It is assumed that the area bounded by the undisturbed ground surface and settlement trough is equal to the ground volume loss caused by tunneling operations
Summary
Until about 1900, Large sewers were generally constructed of brick. It was common to build the sewer structures as a combined brick masonry and concrete [1],[2]; the concrete was used for the foundation of brick sewer or for reinforcing or backing up brick arches such that inverts were built out of concrete and arches were built out of bricks [3]. Several layers of brick were used to construct municipal sanitary sewer lines. Thousands of miles of brick sewer lines are still in service in cities such as Washington DC, London, Paris, etc [3]. Further development of cities results in the need for improved infrastructure systems. Subsurface structures such as tunnels are becoming more desirable for infrastructure projects as spaces on the ground are limited[4]. Heydarpour was with The George Washington University, DC, 20057 USA He is with Subsurface and Tunnel Engineering LLC, Frederick, MD 21704 USA (e-mail: parsa.heydarpour @gmail.com). Ground movements depend on tunnel geometry and depth, excavation methods, workmanship quality, and geotechnical conditions. It is widely accepted that a transverse section of the Greenfield settlement trough can be obtained with acceptable precision by a reversed Gaussian curve
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