Construction of Water Tight Shafts in a Restricted Access Environment-PPT Presentation

PPT Presentation

Pdf Summary

The presentation describes the construction of watertight shafts in a restricted-access environment and the adjustments made between the contract design and the contractor’s redesign.<br /><br />The project faced variable soil conditions, including challenges tying the shafts into rock and controlling column deviation. The team responded by adjusting column sizes and design parameters and modifying construction procedures. Working-platform stability also required attention.<br /><br />Restricted space and low headroom limited rig access, prompting changes to the jetting procedure. Construction sequencing also had to account for nearby train-track footers. Utility interactions raised concerns about design, potential undermining, and the need for careful preparation and coordination. The presentation identifies communication and adapting micropiles to provide additional lateral support for the support-of-excavation system as key responses.<br /><br />A test program included ACI testing, coring, and permeability testing. Reported core-break strengths were 529 psi for the test program and 931 psi for production cores. The presentation also includes hydraulic-conductivity results for fill, a presumed varved layer, and test and production piezometers.

Keywords

watertight shafts

restricted-access environment

contract redesign

variable soil conditions

column deviation

micropiles

support of excavation

hydraulic conductivity

permeability testing

low headroom