REMEDIAL STRATEGIES FOR SHRINK SWELL SOILS: TEXAS EXPERIENCE

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1 REMEDIAL STRATEGIES FOR SHRINK SWELL SOILS: TEXAS EXPERIENCE Anand Puppala, Ph.D., P.E., F. ASCE Professor & Associate Dean-Research The University of Texas at Arlington Arlington, Texas Presentation 57 th Annual Transportation Conference Feb 11-12, 2014

2 Agenda Ø Problematic Soils v Expansive Soils Ø Shallow Stabilization Ø Stabilization Design Guidelines v Durability of Stabilization Ø Sustainability Stabilization Ø Deep Stabilization Deep Soil Mixing Ø Summary

3 Exp e nsive Exp a nsive Soils 3

4 Expansive Soils geotechnical/98139/images/04_fig37.jpg

5 Ø Expansive soils Expansive Soils bowing-walls/expansive-soils/wall-failure-hydrostatic-pressure-lg.jpg

_sl500_pisitb-stickerarrow-big,topright,35,-73_ou01_ss500_.jpg http://www.

6 Expansive Soils 2 Types of pavement damage induced by natural expansive soils Expansive Subgrade Groundwater Table Damage caused by differential heaving Dried and Extremely Brittle Subgrade Longitudinal cracking caused by shrinkage

Table Damage caused by differential heaving Dried and

7 Expansive Soil Induced Failures Limitations of current Swell Characterization and Soil Stabilization Guidelines Focus on Shallow and Deep Stabilization Methods 7

8 Shallow Stabilization of Expansive Soils

9 Common Stabilizing Agents Ø Primary Stabilizing Agents v Lime, L v Portland Cement, C v Fly Ash, FA Ø Secondary Stabilizing Agents v Cement Kiln Dust (CKD) v Ground Granulated Blast Furnace Slag (GGBFS)

10 Lime Stabilization Ø Quick lime (CaO); Hydrated Lime (Ca(OH) 2 ); Slurry Lime Ø High ph, Cationic Exchange and Pozzolanic Reactions Quick Lime Hydrated Lime Slurry Lime

com/full-images/quicklime-powder-801699.jpg Hydrated Lime http://southtexaslime.

11 Typical Lime Stabilization Process

12 Cement Stabilization Ø Calcium based stabilizer Ø Similar enhancements such as lime + High strength Ø Requires lower amounts than lime for stabilization Ø Heavily used in pavement applications

stabilization Ø Heavily used in pavement applications http://3.bp.

13 Cement Stabilization

14 Sulfate Induced Heave Distress (L/C) Source: Wimsatt,1999 Source: Pat Harris Source: Les Perrin, USACE

15 Stabilization Design - Subgrade Additive Selection Criteria for Subgrade Material Using Soil Classification TxDOT Guidelines

16 Premature Failures After Treatment of Subgrades

17 Limitations of current stabilization methods Based on PI and ph values Soils with same PI are not necessarily the same Stabilizers are not effective for all soil conditions Leaching and Permanency problems Design methodologies do not account for Clay Mineralogy Soil LL PL PI A B

effective for all soil conditions Leaching and Permanency problems Design

18 Clay Mineralogy Soil Name Liquid Limit Plastic Limit Plasticity Index Dominant Clay Mineral Bryan Kaolinte Fort Worth Montmorillonite Paris Montmorillonite Pharr-B Kaolinite Chittoori, B.S., and Puppala, A.J. Quantification of Clay Mineralogy ASCE, Journal of Geotechnical and Geoenvironmental Engineering, November, 2011, Vol.137, No.11, pp

Pharr-B 56 19 37 Kaolinite Chittoori, B.S., and Puppala, A.J.

19 Wetting/Drying Durability Studies Ø Simulate seasonal moisture fluctuations ASTM D 596 Method v 42 hours of Drying at 104ºF v 5 hours of wetting (One complete cycle) (a) (b) (a) Wet and (b) Dry cycles setup used by Hoyos et al. (2005) (a) Wet and (b) Dry cycles setup used by Chittoori (2008)

of wetting (One complete cycle) (a) (b) (a) Wet and (b) Dry cycles setup

20 W/D Studies DRYING WETTING

21 W/D Studies At the start After 3 cycles After 5 cycles After 7 cycles Lime Treated Paris Clay

22 Durability Results: Bryan Clay 15 Untreated Treated 10 20% ΔV/V (%) 5 0 WETTING 6% DRYING Additive Type: Lime Additive amount: 8% Dominating Clay Mineral Kaolinite Number of Cycles Change in volumetric strain with different W/D cycles

23 Results: Fort Worth Clay Untreated Treated % WETTING V/V(%) % -15 DRYING Additive Type: Lime Additive amount: 6% Dominating Clay Mineral Montmorillonite Number of Cycles Change in volumetric strain with different W/D cycles Change in volumetric strain with different W/D cycles

24 Recommended design chart Determine PI and %M %M = Percentage Montmorillonite PI = Plasticity Index of the soil If PI < 35 If PI 35 % M < 40 % M 40 % M < 40 % M 40 Use standard design procedure for optimum stabilizer dosage Dosages of Lime (> 8%) and Cement ( 6%) are recommended Durability studies are needed to validate the optimum stabilizer dosage

25 Deep Stabilization of Expansive Soils

26 TxDOT RESEARCH OBJECTIVE To evaluate the application of DM technology in stabilizing expansive subsoils of considerable depths, which in turn will minimize the structural damages caused to pavements due shrink-swell behavior of these soils. FHWA-RD (Snethen, 1979)

27 Deep Soil Mixing Ground modification by mixing in situ soil with a binder (cement, lime) to produce treated columns using specially designed equipment. COLUMNS WALL LATTICE BLOCK

28 GL h i 1 2 i Lime-Cement Column Expansive Soil; C s,comp Fill,e, p ' o s,comp and p ' f,comp Depth of Active Zone, H n

29 Location of Test Sections Sampling Lab study Site 1 (Moderate PI) Site 2 (High PI)

30 Shrinkage Strain Patterns For Binder dosage: 200 kg/m 3, Binder proportion: 25:75 (L:C) & Curing period: 7 days untreated w/c ratio = 0.8 w/c ratio = 1.0 w/c ratio = 1.3 v The behavior is observed to be similar for other dosage rates and curing periods, LS < 0.4%

31 Free Swell Strains Site 1 Untreated w/c = 0.8 w/c = 1.0 w/c = 1.3 Site 2 Untreated w/c = 0.8 w/c = 1.0 w/c = 1.3 v Treated soils for all combinations of binder dosages and proportions recorded swell potentials near to zero

32 Design of DM Columns: Formulation v Heave Prediction (Fredlund and Rahardjo, 1993) ΔH = 1 [ s, comp o (1 + e ] C ) H log[ C s, comp = C s,col a r + C s, soil (1-a r ) p s, comp = p s,col a r + p s, soil (1-a r ) 0 Arrangement of DM Columns p p f s ] a col a soil a r = a soil acol + a col πd = s s

33 Details of DM Columns & Binders in the Field Site 1 Site 2 PI Moderate (22-39%) High (48-50%) Area ratio 25% 35% Dosage Rate (kg/m 3 ) Length ft ft Diameter 2 ft 2 ft Spacing (c/c) 3.5 ft 3 ft Binders Lime & Cement Lime & Cement Proportions 25:75 25:75 w/b ratio No. of Columns Site Dimensions ft ft

34 Schematic of Treated Ground Column Length: ft Length of Anchor: 2 3 ft Rods Ht. of fill = 1.2 ft Note: Not to scale

35 Field Construction and Instrumentation Lime slurry mixing tank Lime-cement slurry mixing tank In Situ Soil- Binder Mixing Lime slurry mixing Lime-cement slurry mixing Auger Spoil Soil-lime-cement columns

36 Geogrid Placement & Anchoring Placing geogrid Anchoring geogrid with DM column Site 1 Completed test sites Site 2

37 Typical Elevation Surveys (Shrink/Swell): Site b/w 2 columns b/w 4 columns untreated Site 1 Initial reading on 7/26/05 Shrink / Swell (in.) /28/05 9/5/05 12/14/05 3/24/06 7/2/06 10/10/06 1/18/07 4/28/07 8/6/ in. Time Note: Total Station 0.2 mm for 50 m

38 Soil movements during monitoring period Overall absolute movement (shrink+swell) w.r.t initial elevations Site Horizontal Inclinometer (HI) Surveying Center East edge West edge Total Station (TS) Surveying b/w 4 columns b/w 2 columns untreated Treated sites experienced low soil movements in vertical direction

39 Design Chart & Comparison -3.5 Heave (in) Heave (in) C s, soil = 0.05 C s, soil /C s, col = 10 γ bulk = pcf C Fill ht. s, soil = 0.05 > 1.5 ft γ C fill > s, 110 soil /C pcf s, col = 10 γ bulk = pcf Fill ht. > 1.5 ft γ fill > 110 pcf p s ',soil (psi) 7 10 p s ',soil (psi) Untreated treated section edge treated section center Depth, z Swell Pressure (1-a r )P s P o P s Area ratio (a r ), % Swell Index, C s of Area 0.1 ratio (and r ), % 0.2

40 Summary Ø Shallow and Deep soil stabilization of expansive soils Ø Clay Mineralogy Details Ø Durability related issues v Wet/dry or freeze/thaw cycles v Stabilizer leaching Ø Deep soil mixing can be effective Ø Benefits of sustainable soil stabilizations

41 Important References Chittoori, B.S., and Puppala, A.J. Experimental Studies on Stabilized Clays at Various Leaching Cycles. ASCE, Journal of Geotechnical and Geoenvironmental Engineering, October, Pedarla, A., Chittoori, S. B., Puppala, A.J. Influence of Mineralogy and Plasticity Index on the Stabilization Effectiveness of Expansive Clays. Journal of the Transportation Research Board, National Academy of Science, Transportation Research Board, 2011, No.2212, pp Madyannapu, R.S., Puppala, A.J., Nazarian, S. and Yuan, D. Quality Assessment and Quality Control of Deep Soil Mixing Construction for Stabilizing Expansive Subsoils ASCE, Journal of Geotechnical and Geoenvironmental Engineering, January, v 136, n 1, 2010, p Chittoori, B.S., Puppala, A.J., Reddy, R.K., Marshall, D. Sustainable Reutilization of Excavated Trench Material. ASCE GeoCongress, 2012, Oakland, California, March 2012, pp

42 Focus on Shrinkage Measurements - Innovation Shrinkage Induced Soil Pressures Tactile Type Sensors

43 THANK YOU Texas DOT Research Sponsor Prof. J. Brian Anderson Auburn University Alabama DOT

44 Research Variables Soil types Dosage rate Description Binder proportions: Lime:Cement (L:C) Variables 2 [medium and high PI] 3 [100 (6%), 150 (9%) and 200 (12%) kg/m 3 )] 4 [100:0, 25:75, 75:25, 0:100] Curing time (days) 2 [7 and 14] Water-binder ratio (w/b) 0.8, 1.0 and 2.0

Mitigation of Expansive Soils Damages

Mitigation of Expansive Soils Damages Joseph Muhirwa Richard Benda Robert Sargent REU Program University of Texas at Arlington This presentation will focus on four main sections Introduction and Background