The two underground stations and portals of Metro Gold Line\u27s East Los Angeles extension were excavated in heavily over-consolidated alluvium. The excavations were supported with heavy soldier piles with pre-loaded steel-pipe struts. When measured strut loads increased to up to 3 times the design value, and strut-waler connections began to buckle, the contractor was directed to install additional struts. Maintaining that the problem had been caused by inadequate construction means and methods, the owner denied a change-order request for this work. This paper describes the contractor’s investigation into the cause of strut overloading in preparation for a formal hearing by a Dispute Resolution Board. The study concluded that the extremely high bracing loads were caused by high in-situ stresses in the region, which had not been accounted for in the shoring-pressure diagrams provided in the contract drawings
