Compared with the drill and blast method, TBM tunnelling has significant advantages with high construction efficiency, low project cost, conducive to environmental protection, favorable stability contr.
[pdf] Sandvik DTH hammer designs offer high power and air efficiency, reducing operating costs and carbon dioxide emissions from drill rigs. These hammers work with various industry-standard shanks and a wide range of standard-size hammers.
[pdf] The name Bertha, after Seattle's first female mayor, , was chosen by a panel (that included the Governor and Transportation Secretary) from 150 submissions from kindergarten through 12th graders, who were asked to submit female names with Washington state heritage. The winning entry, which was submitted by two elementary schools in and , was selected in December 2012.
[pdf] 
