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Using an Existing Tunnel to Dewater the St. Peter Sandstone
Many of the stormwater tunnels in the Twin Cities area are within the weakly cemented St. Peter sandstone. Although its friable nature makes it conducive for tunneling, the presence of water flow induced piping features can result in unpredictable groundwater behavior and unstable ground conditions, which are often not detected by conventional geotechnical drilling. Many of the stormwater tunnels constructed during the early–mid 20th century are undersized for storm events which results in surcharging. Cyclic surcharging has led to damage of the concrete tunnel liner and in many instances has resulted in erosion of the Sandstone behind the liner. The authors present in this paper a unique approach to solve the challenge of groundwater inflow during new access shaft construction. By using the hydraulically conductive nature of the Sandstone, drainage holes were installed along the invert of the existing stormwater tunnel, dewatering the shaft, and allowing the project to continue.
Using an Existing Tunnel to Dewater the St. Peter Sandstone
Many of the stormwater tunnels in the Twin Cities area are within the weakly cemented St. Peter sandstone. Although its friable nature makes it conducive for tunneling, the presence of water flow induced piping features can result in unpredictable groundwater behavior and unstable ground conditions, which are often not detected by conventional geotechnical drilling. Many of the stormwater tunnels constructed during the early–mid 20th century are undersized for storm events which results in surcharging. Cyclic surcharging has led to damage of the concrete tunnel liner and in many instances has resulted in erosion of the Sandstone behind the liner. The authors present in this paper a unique approach to solve the challenge of groundwater inflow during new access shaft construction. By using the hydraulically conductive nature of the Sandstone, drainage holes were installed along the invert of the existing stormwater tunnel, dewatering the shaft, and allowing the project to continue.
Using an Existing Tunnel to Dewater the St. Peter Sandstone
Zimmermann, Joshua T. (author) / Pullen, Thomas S. (author)
Geo-Congress 2020 ; 2020 ; Minneapolis, Minnesota
Geo-Congress 2020 ; 240-249
2020-02-21
Conference paper
Electronic Resource
English
Using an Existing Tunnel to Dewater the St. Peter Sandstone
| British Library Conference Proceedings | 2020
| Engineering Index Backfile | 1943
Engineering Index Backfile | 1933
Wellpoints dewater below sea level
| Engineering Index Backfile | 1948
Engineering Index Backfile | 1930