Coordinated Systems Consulting was approached by the utility client to develop a solution for a current problem with a new service introduction into an existing manhole. New services are being introduced through the 14” sidewall of the existing brick manhole. Currently multiple utilities occupy this manhole for other services leasing to a limited space for access and its proximity to the street reduces the excavation limits. To install the new utility extension, a hole needs to be cut in the sidewall of the brick manhole, this extension can either be cast in place or a precast element. Due to the age of the manhole it was determined the brick wall was minimally reinforced and did show some signs of aging and disrepair. The main concern was potential issues with collapse of the wall when the 4’x4’ opening is being cut through this sidewall.

PICTURED:
The original wall condition inside of the shared manhole space.

Working with the supervising contractor and the engineer, Coordinated Systems Consulting developed a solution using Surtreat® products and glass composite materials. Glass composite was used due to the electrical services within the manhole that prevented carbon fiber from being used. The objective of the operation was to ensure the existing wall is fully stabilized for the cutting operations and to ensure the safety of the men within the manhole. The use of Surtreat® on the existing brick and mortar beds was imperative. The Surtreat® products migrate through the porous brick and mortar and densify the material ensuring a sound substrate for the bonding of the composite materials. After the Surtreat® products were applied and cured the surface was checked and all voids were filled to ensure a smooth surface for bonding. Unforeseen surface irregularities were discovered on the exterior face where additional utilities or other concrete was discovered out of plane from the vertical exterior surface. These areas were cleaned and coated with thickened epoxy to ensure the surface was as smooth as possible for the application of the glass composite. The glass composite was saturated and installed onto the surface. Anchors were also installed within the vertical face. The anchors are used to assist in pinning the glass composite to the brick surface. These anchors allow for the fiber to be developed into the surface of the brick allowing for capacity to be developed. Due to quick sequencing of scheduling for this project the anchors needed to be fabricated on site using the glass composite. These anchors were installed around the perimeter as shown on the show drawings from the manufacturer.

The interior face of the manhole was also prepped and wrapped per the manufacturers shop drawings. Original design consisted of extending the FRP a width of 10’-0.” This dimension was the assumed width of the brick façade within this manhole. Upon actual installation the composite the brick wall was 8’-6” wide. This area was wrapped and the anchors were installed per the spacing required. The middle 4’x4’ area that will be saw cut was not wrapped intentionally. Stabilizing the surrounding wall will provide the adequate capacity, as the opening is cut, the composite will lose its strength in those areas rendering it negligible. It is also important to note that cutting the composite can heat the epoxy up and “gum up” the blade and cutting machinery. For these reasons the middle area was not wrapped. The system is left to cure for 48 hours then the opening can be cut in the brick and a lentil can be installed to help support the overhead load. After the opening is cut and the lentil is installed, Coordinated Systems Consulting will arrive back on site to inspect the FRP to ensure no issues have developed due to over cutting or general issues with the installation of the lentil. If need be an additional strip of composite can be installed vertically over the face of the lentil on either side to ensure proper stress transfer.

The glass composite was applied to the brick faces to ensure proper stabilization of the brick side wall during the cutting of the 4’x4’ opening. When the top cut was made a steel lintel was slide into the brick face to support the middle area of the brick wall as the bricks below were removed. Coordinated Systems Consulting was brought back on site to ensure any overcut of the fiber due to the lintel installation was rewrapped to sure proper conformity to the intended design. Anchors were recorded as installed within the interior and exterior faces of the brick wall during the installation of the FRP. No photos were taken by the installation crew during these processes. To ensure all parties are comfortable with the quality and installation of the composite reinforcement, additional anchors were installed on June 26th on the interior face of the brick wall.