1817.7 Additional requirements for pit-pier underpinning.
BC § 1817.7
When the method of support selected is pit-pier underpinning, the design shall meet the following minimum criteria: 1. After installation of each pit-pier, the approach pit shall be back filled.
2.In no case shall the general site excavation expose more than one third of the total height of a pit-pier, unless: 2.1. A pit-pier bracing system designed by the engineer is installed or; 2.2. The calculated capacity of the individual pit-pier to resist lateral loading at a greater depth is identified on the drawings.
3.Pit-piers shall be preloaded by wedging, use of permanent jacks, or by other means designed by the engineer.
4.Any voids between the bottom of the foundation and the top of the pit-pier shall be filled with dry-pack or equivalent. Dry-pack shall be composed of nonshrink material and be no more than 3 inches (76 mm) in thickness.
5.The need for jacking and all associated jacking requirements shall be determined by the engineer responsible for the underpinning design.
6.The width of pit-piers shall not exceed 4 feet (1219 mm) unless the calculations determine that a wider pit-pier is acceptable.
7.Shear transfer shall be designed and installed between adjacent pit-piers.
8.The bottom of pit-pier elevation shall be a minimum of one foot below the bottom of the future adjacent excavation. (Am. L.L. 2023/077, 6/11/2023, eff. 6/11/2023) Editor's note: For related unconsolidated provisions, see Appendix A at L.L. 2023/077.
