In excavating trenches for laying large diameter pipe, it is necessary to provide safety for workmen who must enter the trench and support for adjacent utilities during the excavation. Such trenches may vary in depth up to 22 feet and in width from about 6 to 14 feet to accommodate pipe of diameters from 15 to 120 inches. Trench shoring has generally been provided in the past by the use of pilings with sheathing in place outside the pilings and cross beams disposed transversely of the trench line. Construction of such shoring arrangements generally slows the excavation and involves substantial expenditures and labor not directly related to the excavating work itself.
In recent years there have been a number of proposed shoring boxes and cages prefabricated for ready installation into the trench excavation. Such arrangements, however, have not been entirely self-propelled and adjustable to accommodate trenches of varying width and depth and in which the shoring plates or sheathing are movable with a shoring frame which can be raised and lowered into and out of the trench relative to a self-propelled carrier and in which the plates are individually movable relative to the frame.
It is the principal object of this invention to provide an improved self-propelled shoring rig for use in trench excavation of improved versatility and operating efficiency.