Crouting the 'Prairie Sediments'
This paper outlines the type of water-bearing formations encountered in the Prairie Sediments and describes a method for effectively sealing these zones in order that shaft-sinking operations may be carried out with safety. Details are given of the procedure for carrying probe holes ahead of the shaft bottom. These probe or grout holes are employed for establishing a series of overlapping grout covers around the proposed shaft excavation to safeguard against large inflows of water during sinking. The pattern and length of grout covers cannot be standardized, and each cover needs to be specially designed to suit the varying ground conditions. In order to provide effective protection through the Prairie Sediments, the number of holes in any one cover would not be Jess than 8, and possibly as many as 64 would be required in certain zones. The length of covers would vary from 100 ft. to 250 ft. Emphasis is placed on the need for obtaining accurate geological and water information from exploratory holes, drilled in the shaft vicinity, in order to effectively plan ali grout covers. Due to the relatively high water pressures encountered in the section under consideration, the selection of strong and permanent grout materials is stressed. These materials are discussed, as weil as the pumping pressures required for injection. It is considered uneconomic to attempt to seal off ali water prior to sinking. Grouting is carried out, rather, to reduce the flow toward the proposed excavation sufficiently to allow sinking operations to proceed expediently. However, it is necessary to carry a "dry" shaft into the salt beds and, therefore, during the construction of the shaft lining, provision is made for grouting behind it when the concrete has cured. This method is outlined. Careful planning, experienced supervision and the use of suitable safety deviees for the drilling and grouting operations are essential requirements for making grouting the most economical, and, due to its permanency, the most efficient means of dealing with t he formation waters in the Prairie Sediments.
dolomite, grouting, heavy water, Nisku, Souris River, formation, Grout, Grouting, Materials, Operation, Pressure, sediments, Shafts, Water, Waters