DISTRIBUTION OF EXPANSIVE SOILS

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Florence Lyons
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1 HOW TO DESIGN?

2 DISTRIBUTION OF EXPANSIVE SOILS

3 WIDE VARIETY OF CLIMATE

4 SAME SOIL -- DIFFERENT CLIMATE

5 RESIDENCE COMPLICATIONS

6 DESIGN NEEDS ENVELOPES

7 EDGE LIFT

8 EDGE DRYING

9 DESIGN AIDS SOIL MOVEMENT SOIL MOVEMENT TABLES SLAB DEFLECTION AND STRESSES SOIL VOLUME CHANGE SOIL MOISTURE VARIATION DISTANCE VERTICAL BARRIERS

10 SOIL SUCTION

11 EXAMPLE: VOLFLO-2 GIVEN VALUES: U WET U DRY Z m U EQUIL. U O n = 2.50 pf = 4.56 pf = ft = 3.31 pf = 1.03 pf = 1 cycle/year

12 SOIL MOVEMENT

13 SOIL MOVEMENT

14 SOIL MOVEMENT

15 SOIL MOVEMENT

16 SOIL MOVEMENT

17 SOIL MOVEMENT TABLES Design Differential Soil Movement, y m, Guide Number for Slab Design Measured Suction pf at Depth, z m, y m Guide Numbers Controlling Surface Suction, pf m Note: The positive sign indicates heave and the negative sign indicates shrinkage.

18 SOIL MOVEMENT TABLES Design Differential Soil Movement, y m, Guide Number for Slab Design: Lawn Irrigation Measured Suction pf at Depth, z m, m y m Guide Numbers Controlling Surface Suction Due to Lawn Watering pf units With 4 ft. Deep Moisture Barrier pf -- units

19 SOIL MOVEMENT TABLES Design Differential Soil Movement, y m, Guide Number for Slab Design: Flower Bed Case (4 ft Deep Flower Bed Moisture) Measured Suction pf at Depth, z m, m y m Guide Numbers Controlling Surface Suction Due to Flower Bed Watering pf units With 4 ft. Deep Moisture Barrier pf -- units

20 SOIL MOVEMENT TABLES Design Differential Soil Movement, y m, Guide Number for Slab Design: Tree Drying Case (Without Moisture Barrier) Depth of Tree Root Zone, ft y m Guide Numbers Measured Equilibrium Suction at Depth, z m pf -- units Movement active zone, z A = 11.5 ft. Movement active zone, z A = 7.5 ft. Movement active zone, z A = 3.5 ft.

21 SOIL MOVEMENT TABLES Design Differential Soil Movement, y m, Guide Number for Slab Design: Tree Drying Case (With Moisture Barrier) Depth of Tree Root Zone, ft y m Guide Numbers Measured Equilibrium Suction at Depth, z m (With 4 ft Deep Moisture Barrier) pf -- units Movement active zone, z A = 11.5 ft. Movement active zone, z A = 7.5 ft.

22 SLAB DEFLECTIONS AND STRESSES EXAMPLE NO. 1 P.T.I. DESIGN MANUAL FLAT SLAB RIBBED SLAB

71 SOIL VOLUME CHANGE CHARTS NATURAL RESOURCES CONSERVATION SERVICE U.S.D.A. DATA BASE (130,000 SAMPLES)

72 EXPANSIVE SOILS ZONES (A. P. COVAR) B-Line PLASTICITY INDEX, % PI = 0.90(LL-8) U-Line Upper Limit of Chart (PI=LL) Any mineral plotting in this zone should be included in ZoneI Montmorillonite 10 VII Halloysites V VI I II PI = 0.85(LL-11) Mixed Minerals PI = 0.81(LL-14) Illites Kaolinites Chlorites LIQUID LIMIT, % PI = 0.73(LL-20) A-Line III IV VIII PI = 0.68(LL-25)

73 EXPANSIVE SOIL VOLUME CHANGE GUIDE NUMBER (A. P. COVAR) ZONE 1

74 EXPANSIVE SOIL VOLUME CHANGE GUIDE NUMBER (A. P. COVAR) ZONE 2

75 EXPANSIVE SOIL VOLUME CHANGE GUIDE NUMBER (A. P. COVAR) ZONE 3

76 EXPANSIVE SOIL VOLUME CHANGE GUIDE NUMBER (A. P. COVAR) ZONE 4

77 EXPANSIVE SOIL VOLUME CHANGE GUIDE NUMBER (A. P. COVAR) ZONE 5

78 EXPANSIVE SOIL VOLUME CHANGE GUIDE NUMBER (A. P. COVAR) ZONE 6

79 EXPANSIVE SOIL VOLUME CHANGE GUIDE NUMBER (A. P. COVAR) ZONE 7

80 EXPANSIVE SOIL VOLUME CHANGE GUIDE NUMBER (A. P. COVAR) ZONE 8

81 VOLUME CHANGE COEFFICIENT, γ h = PERCENT FINE CLAY VOLUME CHANGE GUIDE NUMBER

82 EDGE MOISTURE VARIATION DISTANCE, e m, ft

83 e m (ft), Edge Moisture Variation Distance EDGE MOISTURE VARIATION DISTANCE CENTER LIFT α(cm 2 /sec), Unsaturated Diffusivity Coefficient 0.0E+0 1.0E-3 2.0E-3 3.0E-3 4.0E-3 5.0E-3 6.0E-3 7.0E-3 8.0E-3 VOLUME CHANGE COEFFICIENT (SUCTION COMPRESSION INDEX, γ h ) EDGE LIFT S, Slope of pf--vs--water Content Cuve Percent Passing #200 Sieve (%) LIQUID LIMIT (LL, %) PLASTICITY INDEX (PI, %) -30

84 EFFECT OF VERTICAL MOISTURE BARRIER

85 MOISTURE BARRIER (T = 1.5 ft) Edge Moisture Variation Distance for Moisture Flow, em, ft Depth of Perimeter Beam Below Ground Level or Depth of Vertical Moisture Barrier Below Ground Level, D', FT 6'--5.5' 5' 4.5' 4' 3.5' 3' 2.5' 2' 1.5' 1' D ' T = 1.5 FT Design Value of the Edge Moisture Variation Distance, e' m, ft. T e m '

86 MOISTURE BARRIER (T = 2.0 ft) Edge Moisture Variation Distance for Moisture Flow, em, ft Depth of Perimeter Beam Below Ground Level or Depth of Vertical Moisture Barrier Below Ground Level, D', FT 6' 5.5' 5' 4.5' 4' 3.5' 3' 2.5' 2' 1.5' 1' D ' T T = 2 FT e m ' Design Value of the Edge Moisture Variation Distance, e' m, ft.

87 MOISTURE BARRIER (T = 2.5 ft) Edge Moisture Variation Distance for Moisture Flow, em, ft Depth of Perimeter Beam Below Ground Level or Depth of Vertical Moisture Barrier Below Ground Level, D', FT 6' 5.5' 5' 4.5' 4' 3.5' 3' 2.5' 2' 1.5' 1' D ' T T = 2.5 FT e m ' Design Value of the Edge Moisture Variation Distance, e' m, ft.

88 DESIGN AIDS FOR SLABS ON EXPANSIVE SOILS

4. Soil Consistency (Plasticity) (Das, chapter 4)

4. Soil Consistency (Plasticity) (Das, chapter 4) 1 What is Consistency? Consistency is a term used to describe the degree of firmness of fine-grained soils (silt and clay). The consistency of fine grained