Approach According to Masopust

The load-settlement curve of a single pile is constructed in the following way:

1) The ultimate skin friction q_s is determined as follows:

where:	a,b	-	regression coefficient of the specific skin friction
	v_i	-	depth from terrain up to the middle of the i^th layer [m]
	d_i	-	pile diameter in the i^th layer [m]

and pile skin bearing capacity is provided by:

where:	m₁	-	load type coefficient
	m₂	-	shaft protection coefficient
	d_i	-	pile diameter in the i^th layer [m]
	h_i	-	thickness of the i^th layer [m]
	q_si		ultimate skin friction in the i^th layer [MPa]

2) The pile base bearing capacity q_b follows from:

where:	e, f	-	regression coefficients below the pile base
	D	-	pile length inside soils [m]
	d_b	-	pile base diameter [m]

3) The proportion of applied load transferred to pile base β is written as:

where:	q_b	-	pile base bearing capacity [MPa]
		-	weighted average of ultimate skin friction [MPa]
	D	-	pile length inside soils [m]
	d_b		pile base diameter [m]

The load at the mobilization of skin friction R_sy is then given by:

where:	R_s	-	pile skin bearing capacity [N]
	β	-	proportion of applied load transferred to the pile base [-]

4) The load at the shaft resistance activation (= mobilization of skin friction) R_sy is given by:

where:	I_s	-	settlement-influence factor
	R_sy	-	load at the mobilization of skin friction [N]
	d	-	pile diameter [m]
	E_s	-	secant modulus of soil along the pile shaft [MPa]

5) The load at the pile base for the prescribed settlement (for limiting settlement of 25 mm) follows from:

where:	β	-	proportion of applied load transferred to the pile base [-]
	R_sy	-	load at the mobilization of skin friction [N]
	s_lim	-	limit settlement (usually prescribed as 25 mm) [m]
	s_y		settlement at shaft resistance activation [m]

and the pile resistance attributed to a given limit settlement s_lim is then provided by:

where:	R_b,lim	-	load on the pile base for prescribed settlement [N]
	R_s	-	pile shaft resistance [N]

Approach according to Masopust

Literature:

Masopust, J.: Vrtane piloty. 1^st edition, Prague, Cenek a Jezek, 1994, 263 p.

Masopust, J., Glisnikova, V.: Zakladani staveb Modul M01. 1^st edition, Brno, AN CERM, 2007, 182 p., ISBN 978-80-7204-538-9.

GEO5