Helping Hand

Rebhann (1871) gave this graphical procedure for locating the slip plane and determining the total active earth pressure according to Coulomb’s wedge theory.   Procedure:- 1) Draw A retaining wall having height H i.e. AB 2) Draw three lines   Ground Line ( ß @ with horizontal)                                   Failure Line ∅                                     Earth pressure line  Ψ   3) Through point A Draw a line parallel to Ψ   line which cuts BD line at point C. 4) Through C draw perpendicular line CE which cuts an arc at E. 5) Join BE line consider BE as a radius and B as a center draw an arc through E       which cuts at point F on BD line. Through F draw a line parallel to  Ψ line which       cuts line AD at point G. 6) Consider GF as a radius and F is a centre. Draw an arc through G which cuts BD      at point H. Join GH to form a triangle GHF. 7) Consider GI is a height of triangle that is x. Through point B draw a line

Active earth pressure, passive earth pressure and at rest earth pressure  

Culmann's Graphical Method           Culmann's Curve is the curve use to find Active and Passive Earth Pressure in Retaning wall.  Culmann's curve is drawn using Culmann's Graphical Method. In this article we describe the step by step procedure how to draw culmann's curve and how to find Active Earth Pressure Using Culmann's curve. Procedure: 1) Draw Ground Line , Failure Line & Earth Pressure Line with β, 丫 , ψ angle respectively. 2) Consider any trial wedge ABC 1  and measure length AC 1  as a L 1 3) Calculate the weight of wedge ABC 1  and plot it at point E i.e. BE 1 =L 1 4) Consider all such lines BC2, BC3, BC4, and corresponding points E 1 , E 2 , E 3 , E 4 . 5) Through E 1  draw a line parallel to ψ line which cut's BC 1  at point F 1 . 6) Draw similar lines F 2 E 2 , F 3 E 3 , F 4 E 4 . 7) Draw a smooth curve which passes through B, F 1 , F 2 , F 3 , F 4 . This curve is called as     

Well graded soil:- It shows good representation of diameter of each particles. Poorly graded soil / Uniformly graded soil:- Single diameter of particle exceed in a soil. eg. Aeoline soil. Gap graded soil :- Sum particles are more in quantity, where sum particles missing in soil.  Grain Soil Distribution Curve   Classification of soil  Diameter / size                                      Soil type   1) <2u                                                           clay 2) 2u - 75u                                                    Silt 3) 75u - 425u                                    Fine sand  4) 425u - 2mm                                   Mid sand 5) 2mm - 4.75 mm                        Fine Gravel 6) 4.75 mm - 20 mm                    Fine Gravel 7) 20mm - 80mm                     Coarse Gravel 8) 80mm - 300mm                               Cobble 9) >300mm                                         Boulder Symbols          Sr.                   Sym

To determine equivalent permeability in stratified soil deposits.   (1)  When Direction of Flow is parallel (horizontal) to strata.   The Total discharge Q is the sum of discharge through individual layers (strata) hence Q=Q 1 +Q 2 +Q 3. Let Z 1 , Z 2 , Z 3  within thickness of each layer where as K 1 ,K 2 ,K 3  within coefficient of permeability for individual layers respectively as shown in figure. The piezometric head for each layer remains constant i.e. h=h 1 =h 2 =h 3   Hence equivalent permeability in horizontal direction i.e. 'x' is Kx or KH = K 1 Z 1 +K 2 Z 2 +K 3 Z 3                                                  ---------------------------------                                                              (Z 1 )(Z 2 ) ( Z 3 ) (2)  When Direction of Flow is perpendicular to strata The Total discharge Q remains same through each layers (strata) hence Q=Q 1= Q 2= Q 3. Let Z 1 , Z 2 , Z 3  within thickness