TIMKKlMNi; 



STl:rTTIN(i 



49 



Fio 



rutting for Shaft". 



compartments. When the material penetrated is very compact, 

 and caving is not likely, a single series of transverse struts, one 

 above the other, running from the top to the bottom of the 

 shaft, as shown by Fig. 26, is used to divide it into two com- 

 partments. In softer material, where the sides of the shaft 

 require support, Fig. 27 

 shows a form of strutting 

 commonly employed. It 

 consists of vertical corner 

 posts braced apart at inter- 

 valslty fourhorizontal struts 

 placed close to the walls of 

 thr shaft. The longer side 

 struts are also braced apart 

 at the center by a middle strut which divides the shaft into 

 two compartments. A lagging of vertical plank is placed 

 between the walls of the shaft and the horizontal side struts. 

 In very loose soils the form of strutting shown by Fig. 28 is 

 employed. This is practically the same construction as is 

 shown by Fig. 27, with the addition of an interior polygonal 



horizontal bracing in each 

 half of the shaft. Referring 

 to Fig. 28, the timbers a, /. 

 etc., are vertical and con- 

 tinuous from the top to the 

 bottom of the shaft; and 

 the horizontal timlx-rs, />, 6, 

 etc., are spaced at more or 

 less close intervals verti- 

 cally. The lagging plank 



may be laid with spaces between them, or close together, or, 

 in case of very loose material, with their edges overlapping. 

 The manner of constructing the strutting is also governed by 

 the stability of the soil. In firm soils it is possible to sink the 

 shaft quite a depth without timbering, and the timbering can 



FlO. 28. 1(<>iiifi>M-i-<t l:.'<-t:iiii:ul;ir Fr:inn Strut- 

 ting for Snafu In Treaclirrou* Material*. 



