VERTICAL AND INCLINED SURFACES OF SEPARATION 



287 



AB 

 2 



km 



5 10 1-5 2 



Profile W 



■^ 3p-y 4p. ip 



457 458^462^5:=^^^ g^-460jg3g|^3| |^4e2>i46^^^ ^p „465_,^ 466 



468 Ip 



oTo) A(b) — (c) i^ra(d) C=l(e) ==^(f) (g) (h) (i) 



^(j) — (k)---(L) 



Fig. 13. a — VEP points; b — deep drilling holes; c — line of equal 5;^; d — areas of in 

 crease in Qj^; e^areas of decrease in Qi^',f- — line of true values of 5; g — line of reduced 

 values of 5; h — line of increased values of S due to the influence of the western non- 

 horizontal boundary ; i — line of increased values of S due to the influence of the eastern 

 n on -horizontal boundary; j — position of the non -horizontal boundaries; k — abscissae 

 of the maximum decrease in qj^; I — abscissae of the maximum increase in Qj^. 



(Qi k)L > ?2' ^t a distance approximately 400-500 m from the VEP point can 



be assumed on the basis of the diagnostic features of the cross VEP curve. 



We can obtain an idea of the relative variations in the forms of VEP 



curves along the profile by comparing the approximately constructed 



curves for cases a and c with respect to h and d for various values of — — 



u 



(Fig. 1.) and this enables us to determine the position of the non-horizontal 



contact and of the right-hand asymptotic branches of the VEP curves 



(cf. Fig. 5)*. 



* It is here assumed that the thickness of the layer h^ in the raised block (case c in Fig. 1) 

 is sufficiently small by comparison with the thickness of this layer in the lowered block 

 (case a in Fig. 1). 



