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stresses, the borehole pressure can overcome the low stresses, thereby <br />fracturing the soil and allowing water or grout to flow from the <br />ill. When the pressure is removed, the small <br />borehole into the f <br />soil still performs its intended function of <br />fracture closes and the <br />restricting flow through the dam, <br />of <br />Cracks can be caused by (a) differential settlement between portions(c) <br />the fill or foundation, (b) by dessication during construction, <br />and by other mechanisms. Fills which are constructed at water contents <br />below optimum mechanisms. <br />silty or sandy silt materials are more susceptible <br />to cracking than clayey fills, especially when subjected to differential <br />ilt materials al so .tend. to �liow.cracks:to <br />settlements* Silty or;sandY s _.- <br />lay soils that will often "self heal" cracks - <br />stay open, versus c <br />can <br />a coarse <br />Pervious layers or zones within the cam f hained lsoil portion) occur <br />if 1s placed <br />grained or clean material (low fine -g <br />ion of the fill. Such layers, if they <br />unintentionally during construct <br />exist, will occur in horizontal layers due to the method in which a dam <br />is constructed. <br />thered during the grouting program, the cause of the <br />From the data ga <br />how could not be determined <br />water loss, grout take and dye soe <br />Of the dam, <br />cause was important to assessing the general integrity <br />additional investigations subsequent to the grouting program were <br />conducted as discussed in Section 2.2.2• <br />Grout Takes in Foundation t{aterial and Other Observations <br />e within <br />tion <br />,,.. <br />Figure 3 indicates substantial zonas Sigrout #heaek ma tetialshareoriotafine <br />alluvial soils and weathered tock• <br />grained,'. the''tiigh"`grout takesre-'thoughbelndlcative"of"the high <br />r ' Of` units• The grout holes penetrated the Foundation <br />Permeability' presence <br />of high permeabilities <br />materials downstream of the cutoff. The p <br />in this region is, therefore, considered likely- <br />