Salas Theory

The critical force N_cr for basic support conditions in the micropile head (determining micropile deflection) follows from:

where:	E_a*I_a	-	bending stiffness of micropile reinforcement
	l	-	free length of micropile length
	l_ef	-	length of the fictitious fixed end
	A	-	constant reflecting the type of support in micropile head

where:	f	-	coefficient depending on the ratio of modulus of elasticity of soil in micropile head and base
	l_e	-	elastic length of micropile given by:

where:	E_a*I_a	-	bending stiffness of micropile reinforcement
	E_l	-	modulus of elasticity of soil in the micropile base

Literature:

Jiménez Salas J.A. a kol:Geotecnica y Cimientos III, Capitulo 3, Rueda, Madrid (Spanish).

GEO5