Skin Friction of the Micropile Root

Reference values of limit skin friction (recommended by the authors)

Soil	Skin friction [kPa]
soft clay	40 - 60
stiff clay	65 - 85
solid clay	130 - 170
sand naturally wet, loose	110 - 150
sand naturally wet, medium dense	140 - 180
sand naturally wet, dense	170 - 230
aquiferous sand, loose	80 - 130
aquiferous sand, medium dense	120 - 160
aquiferous sand, dense	160 - 200
sandy clay, soft	50 - 70
sandy clay, stiff	75 - 95
sandy clay, solid	125 - 165
clayey sand, wet, loose	90 - 135
clayey sand, wet, medium dense	135 - 165
clayey sand, wet, dense	150 - 170
clayey sand, aquiferous, loose	80 - 105
clayey sand, aquiferous, medium dense	90 - 130
clayey sand, aquiferous, dense	115 - 155

Values of limit skin friction according to DIN 4128

Values of skin friction according to CSN 73 1004

Type of soil	Number of groutings	Final grouting press. [MPa]	plášť. tření [kPa]
bedrock	0	-	650 - 1100
semirock	0 - 1	0.5 - 3.0	500 - 700
sandy gravels	1 - 2	1.0 - 2.0	170 - 250
clayey gravels	1 - 2	2.0 - 4.0	170
sands	2 - 3	1.5 - 4.0	120 - 170
fine-grained soils - very stiff	1 - 3	1.5 - 3.0	100 - 160
fine-grained soils - stiff	2 - 3	1.0 - 2.5	80 - 100
fine-grained soils - firm	3 - (4)	0.5 - 2.0	60 - 80

Recommended parameters of anchor roots (Mišove, Klein, Inženýrské stavby 5/1986)

Type of support of micropile in head	Final grouting press. [MPa]	Number of groutings	Root diameter [mm]	Root length [m]	Skin friction [kPa]
bedrock	-	0	120	5 - 3	1000 - 1600
semirock	0.5 - 3.0	0 - 1	120 - 220	7 - 3	300 - 1000
gravel, injectable soils	1,0	1 - 2	250 - 400	7 - 5	250 - 320
gravel, non-injectable soils	2.0 - 4.0	1 - 2	280 - 350	7 - 5	230
medium and fine-grain sand	1.5 - 4.0	2 - 3	220 - 350	12 - 7	150 - 180
cohesive stiff and solid soils	1.5 - 3.0	1 - 3	200 - 280	17 - 8	130 - 190
cohesive solid to rigid plastic soils	1.0 - 2.5	2 - 3	150 - 400	20 - 9	100 - 130
cohesive soft plastic soils	0.5 - 2.0	3 - 4	300 - 450	27 - 13.5	50 - 70

GEO5