Un-hardening Phenomenon of SCW (Soil Cement Wall) Built in Organic Soils Chung R. Song, Ph. D, PE...
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Transcript of Un-hardening Phenomenon of SCW (Soil Cement Wall) Built in Organic Soils Chung R. Song, Ph. D, PE...
Un-hardening Phenomenon of SCW
(Soil Cement Wall) Built in Organic Soils
Chung R. Song, Ph. D, PE
Department of Civil EngineeringThe University of Mississippi
University, MS 38677
Presentation Order
Job site description Problem description Researches Remedy
Job Site DescriptionDeep Excavation
• East coast of South Korea (Samchuck)
• Deep Excavation D≈20m
• Strut + SCW Wall
• Ground Condition
-Fill: GL.-0.5 to -0.7 m, Loose
-Alluvium sands, silts, clays : GL.-0.7 to 18.6 m, N=2 to 13
-Weathered zone: GL.-15.5 to -19.3, N>40
Problem DescriptionConstructed SCW did not solidified!!
Clayey soils were suspected as the culprit.
Took the clay samples and performed lab. tests.
No. Natural Water Content (%)
Liquid Limit (%)
USCS Organic Content (%)
1 43 35.2 CL
2 44 33.2 OL N.A.
3 N.A. 39.2 OL 4.82
4 N.A. 34.2 OL 4.82
Based on lab. test results, the culprits were narrow down to the clayey soil itself and organic materials.
Expected Strength of SCWq
u
(kg/c
m2)
Curing Time, Day
qu (
kg/c
m2) san
d
clay
Typical Cures for Hardening Trouble of Clayey Soils and Organic Soils
Item Chemicals
Clayey Soils
Add cement, lime, NaOH, and(or) Ca(OH)2
Organic Soils
Add cement, CaCl2, Ca(OH)2, and(or) NaSiO2
Lab. tests were carried out with above chemicals mixed with field soils.
Lab. Test Results
Curing Time, Days
qu (
kg/c
m2)
CaCl2 2% + additional 20% cemement
additional 20% cemement
NaSiO2 2%
Initial design mix
soil:cement:bentonite:water=600:93:8.3:150
Field Prescription & Results
CaCl2 2% + additional 22% cement was prescribed considering the poor mixing condition in the field.
When applied to the job site, the SCW walls were hardened nicely. Shovel excavation was not possible.
Conclusions
•SCW hardening trouble was caused by the organic clayey soil in the job site.
•To effectively control the hardening trouble in the job site, additional cement and Calcium chloride turned out to be most effective.
•Addition of Sodium silicate di-oxide increased the initial strength but decreased the long term strength, and therefore it was not prescribed for this project.