TUNNELING UNDER THE APACHE TRAIL

Abstract A short tunnel has been constructed to provide access to the raised crest of Theodore Roosevelt Dam. Field and laboratory data, rock mass classification, and block theory were used to design the basic rock support. A unique aspect of the tunnel is that it crosses beneath a highly used Arizona state highway known as the Apache Trail, with limited rock cover between the tunnel and the highway. Special measures were taken to ensure continued use of the highway during construction. The design was effective in that little movement was measured in the rock beneath the roadway during or following construction.