A method is provided for centering and guiding a large diameter soil processing tool. A sacrificial guide is formed by using a small diameter soil processing tool to form a soil-cement column having a relatively hard outer section and a relatively soft center section. The relatively hard outer section is utilized to guide the large diameter soil processing tool. In one embodiment, the soft central region of the sacrificial guide is left in place and the pilot of the large tool carries an auger that simply drills through the central portion of the sacrificial guide. In a second embodiment, the sacrificial guide is hollow and the large tool need not have an auger at the tip of its pilot. The large tool advances downwardly through the sacrificial guide and, as it advances downwardly, the large tool breaks up the sacrificial guide and the sacrificial guide particles ultimately form a portion of the soil-cement column formed by the large soil processing tool. The method facilitates the use of soil processing tools having diameters of 8 to 20 feet, for example. Large volumes of subterranean material may be hardened or solidified by using an array of the sacrificial guides to precisely control and center the large processing tool so that the large quantities of subterranean material such as utilized to support an airport runway may be processed efficiently with the invention. The method is also usable with soil processing tools of any diameter.