Chapter 6 Test Results
6.3 Cyclic Torsional Shear Test
6.3.4 Cone Resistance Change Due to Cyclic Torsional Shearing
The change of CPT cone resistance in the fill due to cyclic shearing compaction is studied in this section. Fig. 6.38 to Fig. 6.42 shows the test result of cone resistance after 20 cycles of shearing at different the shearing angles. The cone resistance for loose sand and statically loaded sand are also shown in the figures. Fig. 6.38 shows, the cone resistance qc has increased after compaction at shearing angle
= ±1°. Fig.
6.39 to Fig. 6.42 show the tip resistance qc at shearing angles of ±3°, ±5°, ±7° and
±10°. As compared with that for loose fill, statically loaded fill, the cone resistance increased signification due to compaction. Fig. 6.43 shows the cone resistance increased significantly after cyclic shear compaction. Fig 6.44 showed the distribution of normalized qc for uncompacted loose fill. For loose soil, the qc / qc,loose was 1.0. In Fig 6.44, cone resistance ratio increased to about 4 times due to the static loading q = 9.2 kPa. After the application of static and cyclic shear compaction, the cone resistance increased up to about 6 times. The effects of static vertical load and cyclic shearing on the cone resistance of soil were quite obvious.
Fig. 6.45 to Fig. 6.49 show the cone resistance at different depths were converted to the relative density of soil with the method proposed by Jamiolkowski et al. (1985).
In these figure, the calculated relative density of loose fill was compared with that measured in the lab. In fig 6.48, the test values were neared the calculated relative density at the shearing angle = ±7° at the depth z = 200 mm to 300 mm. The cone resistance was very low at the depth z = 0 mm to 200 mm because of the extremely
40
low overburden and confining pressure. With such a thin soil fill (H = 600 mm), it may not be a good idea to predict the distribution of soil density with the penetration test.
The effective depth of compaction plays an important role in field earthwork.
Compaction with a smooth-wheel vibratory roller can easily reach an effective depth of compaction of 0.3 m. Although the compaction with the cyclic torsional shear compactor suggested in this thesis make low noise and no low vibration, however the effective depth was only compaction of 0.15 m. That means it would require double the number of lifts in the field. It should be mentioned that, the laboratory experimental investigation shown in this study is only preliminary. The effective depth of compaction in construction can be enlarged by properly adjusting the radius of the shearing disc R, the applied normal stress q for construction.
Chapter 7
CONCLUSIONS
In this study, the surface settlement, change of relative density, stresses and cone resistance change in the soil due to static vertical loading, and cyclic torsional shearing compaction were investigated. Based on the experiment results, the following conclusions were drawn.
1. With the vertical loading q = 9.2 kPa on the surface of the four 150 mm-thick soil lift, the induced surface settlements varied from 15.0 to 22.3 mm. The average surface settlement was 19.0 mm, which was about 3.2% of the soil thickness. Static vertical loading is an effective method to compact the loose fill.
2. Static vertical loading represents the dead load of the cyclic torsional shear compactor. After the application of q = 9.2 kPa, on the average, the relative density of soil increased from 35.5% to about 62%, which was less than the target value Dr = 70-85% for dense sand.
3. As compared with that for uncompacted loose sand, the effects of static vertical loading on the vertical and horizontal earth pressure, in the compressed soil mass were not significantly.
4. The application of static vertical loading q = 9.2 kPa significantly increased the cone resistance of the compressed fill. The normalize cone resistance qc / qc,loose increased from 1.0 to 4.6 due to static compression.
5. After 20 cycles of torsional shearing with the rotation angle of
= ±10° on the
surface of the four 150 mm-thick lifts, the average surface settlement was 38.2 mm (volumetric strain = 6.4%). The extra surface settlement due to the torsional shearing compaction was about 19.2 mm. Cyclic torsional shearing compaction (static plus cyclic loads) is an effective method to densify loose soil.6. With static load q= 9.2 kPa and the lift thickness of 150 mm, after 20 cycles of
42
torsional shearing with angle
of ±5°, the relative density achieved was 72 to
84%. The compacted relative density increased with increasing angle.7. The vertical earth pressure in the fill was not influenced by the cyclic shearing compaction. However, after cyclic shearing compaction, the horizontal earth pressure in the compacted fill increased from 27% to 88%
8. After cyclic torsional shear compaction, the normalized cone resistance qc / qc,loose increased from 4.6 to about 9.0. Test results showed the cyclic shearing compaction effects on the cone resistance in the fill was quite obviously.
References
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Compaction.” Master of Engineering Thesis. Dissertation, National Chiao Tung University, Hsinchu, Taiwan.
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Cyclic Settlement,” Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 130 (11), 58-70.
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26. Ishibashi, I., and Sherif, M. A., (1974), “Soil Liquefaction by Torsional Simple Shear Device,” Journal of the Geotechnical Engineering Division, ASCE, 100 (8), 871-888.
27. Ishibashi, I., Kawamura, M., and Bhatia, S. K., (1985), “Effect of Initial Shearing on Cyclic Drained and Undrained Characteristics of Sand.” Geotechnical Engineering Report 85-2, School of Civil and Environmental Engineering, Cornell University, Ithaca, New York, USA.
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29. Jaky, J., (1948), “Pressure in Soils,” Proceedings, 2nd
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30. Jamiolkowski, M., Ladd, C.C., Germaine, J.T. and Lancellotta, R. (1985) “New developments in field and laboratory testing of soils”. State-of-the art report.
Proceeding of the 11th International Conference on Soil Mechanics and Foundation Engineering, San Francisco, 1, 57-153, Balkema Pub., Rotterdam.
31. Johnson, A. W., and Sallberg, J. R. (1960). “Factors That Influence Field Compaction of Soil.” Highway Research Board, Bulletin No. 272.
32. Kramer, S. L., (1996), “Geotechnical Earthquake Engineering”, Prentice-Hall, Inc.,
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Upper Saddle River, New Jersey.
33. Lo Presti, D. C. F., Pedroni, S., and Crippa, V. (1992). “Maximum Dry Density of Cohesionless Soils by Pluviation and by ASTM D 4253-83: A comparative study.”
Geotechnical Testing Journal, ASTM, 15(2), 180-189.
34. Mayne, P. W., and Kulhawy, F. H. (1982). “
K -OCR Relationships in Soil.”
oJournal of Geotechnical Engineering Division, ASCE, 108(GT6), 851-872.
35. McElroy, J. A. (1997). “Seismic Stability of Geosynthetic Reinforced Slopes: A shaking table study.” MS thesis, University of Washington, Seattle, 286.
36. Mesri, G., and Hayat, T. M. (1993). “The Coefficient of Earth Pressure at rest.”
Canadian Geotechnical Journal, 30(4), 647-666.
37. Miura, K., Tsukada, Y., Tsubokawa, Y., Ishito, M., Nishimura, N., Ohtani, Y., and You, G. L., (2000), “Bearing capacity during earthquake of the spread footing reinforced with micropiles.” Proceedings, 12th World Conference on Earthquake Engineering, pp. 1-8.
38. Peck, R. B., and Mesri, G. (1987). Discussion of “Compacted-induced earth pressures under Ko-conditions.” Journal of Geotechnical Engineering, ASCE, 113(11), 1406-1408.
39. Rad, N. S., and Tumay, M. T. (1987). “Factors affecting sand specimen preparation by raining.“ ASTM Geotechnical Testing Journal, 10(1), 31-37.
40. Ren, F. Y., (2006) “A Study on the Influence of Type of Plate Shearing on the Relative Density of Loose Sand,“ Master of Engineering Thesis, Chung Yuan Christian University, Chungli, Taiwan.
41. Seed, R. B., and Duncan, J. M. (1983). “Soil-Structure Interaction Effects of Compaction-induced Stresses and Deflections.” Geotechnical Engineering
Research Report No. UcB/GT/83-06, Univ. of California Berkeley, CA.
42. Sowers, G. F., Robb, A. D., Mullis, C. H., and Glenn, A. J. (1957). “The Residual Lateral Pressures Produced by Compacting Soils.” Proceedings, 4th
International Conference on Soil Mechanics and Foundation Engineering, London, 243-247.
43. Terzaghi, K. (1934). “Large retaining-wall tests (I): Pressure of dry sand.”
Engineering News-Record, 112, 136-140.
44. Terzaghi, K. (1941). “General wedge theory of earth pressure.” ASCE
Transactions, 106, 68-80.
45. Terzaghi, K. (1943). Theoretical Soil Mechanics, Wiley, New York.
46. Tzeng, S. K., (2002). “Horizontal Pressure on an Unyielding Wall due to Strip Loading on Backfill with Different Densities.” MS thesis, Dept. of Civil Engineering, National Chiao Tung University, Hsinchu, Taiwan.
47. Robertson P. K. and Cabal K.L. (Robertson), (2009). “Guide to Cone Penetration Testing for Geotechnical Engineering.” Gregg Drilling & Testing, Inc. Corporate Headquarters 2726 Walnut Avenue Signal Hill, California 90755.
48. US NAVY. (1982). “Foundations and Earth Structures.” NAVFAC Design Manual
DM-7.2. Naval Facilities Engineering Command, U.S. Government Printing
Office, Washington, D. C., 60.49. Vesic, A. S., (1973), “Analysis of Ultimate Loads of Shallow Foundations,”
Journal of the Soil Mechanics and Foundations Division, ASCE, 99 (1), 45-73.
50. Vesic, A. S., Banks, D. C., and Woodard, J. M. (1965). “ An Experimental Study of Dynamic Bearing Capacity of Footings on Sand.” Proceedings, Sixth
International Conference on Soil Mechanics and Foundation Engineering,
Montreal, Canada, II, 209-213.51. Wang, F. J., (2005). “Effects of Adjacent Rock Face Inclination on Earth Pressure at-rest.” MS thesis, Dept. of Civil Engineering, National Chiao Tung University, Hsinchu, Taiwan.
52. Yang, C. T., (2002) “A Study on Plate Shear to Improve Relative Density of Sand,“ Master of Engineering Thesis, Chung Yuan Christian University, Chungli, Taiwan.
53. Youd, T. L., (1972), “Compaction of Sand by Repeated Straining,” Journal of the Soil Mechanics and Foundations Division, ASCE, 98 (7), 709-725.
48
Table2.1. Qualitative description of granular soil deposits Relative density (%)
Table3.1. Characteristics of normal loading discs Thickness
Disc ( mm )
37.5 20.0 10.0 3.0 2.0 1.0
Mass
( kg )
19.80 9.60 4.80 1.55 1.05 0.50
Quantity
Ordered
4 3 1 2 3 4
50
Table 4.1. Properties of Ottawa Sand (after Chen, 2003)
Shape Rounded
emax 0.76
emin 0.50
Gs 2.65
D60 (mm) 0.39
D10 (mm) 0.26
Cu 1.5
Fig. 2.1. Arrangement of uniform spheres (after Deresiewicz, 1958)
52
Fig. 2.2. Unit weight vs. depth relation for vibratory roller compaction (after Whitman and D’Appolonia, 1969)
Fig. 2.3. Compacted unit weight profiles for 8-ft lift heights for 2, 5, 15, and 45 vibratory roller passes (after Whitman and D’Appolonia, 1969)
54
Fig. 2.4. Approximate method for determining lift height required to achieve a minimum compacted relative density of 75% with five roller passes using data for a
large lift height
(after Whitman and D’Appolonia, 1969)
Fig. 2.5. Development of in-situ stresses (after Chen, 2003)
56
Fig. 2.6. Principal Stresses on a Soil Element
x
y
z v
h
hFig. 2.7. Jaky’s Formulation of the Relationship between Ko on OC and
58
Fig. 2.8. Simplified stress history of soil under Ko conditions (after Mayne and Kulhawy, 1982)
(after Mayne and Kulhawy, 1982)
60
Fig. 2.10. Basic components of hysteretic Ko-loading/unloading model (after Duncan and Seed, 1986)
MPLP
Fig. 2.11. Comparison between Final Pressure Distributions Based on Incremental Analysis and Hand Solution (after Duncan and Seed, 1983)
62
Fig. 2.12. Distribution of Horizontal Earth Pressure after Compaction (after Chen and Fang, 2008)
0 5 10 15
Fig. 2.13. Stress path of a soil element under compaction (after Chen and Fang, 2008)
Horizontal Earth Pressure, h (kN/m2)
F : Fill
Horizontal Earth Pressure, h (kN/m2) F : Fill
C : Compaction
Horizontal Earth Pressure, h (kN/m2) F : Fill
C : Compaction
64
Fig. 2.14. Horizontal Earth Pressure Estimated with Various Methods after Compaction (after Chen and Fang, 2008)
Fig. 2.15. NGI cyclic simple shear apparatus (after Airey and Wood, 1987)
66
Fig. 2.16. Stress conditions of a soil specimen cyclic horizontal shear stress
Fig. 2.17. Void ratio versus cyclic displacement for densification of a sand with successive cycles of shear (after Youd, 1972)
68
Fig. 2.18. Sketch of typical results of cyclic simple shear strain-controlled tests with definitions of volumetric cyclic threshold strain (after Hsu and Vucetic, 2004)
Fig. 2.19. Torsional simple shear device (after Ishibashi et al. 1985)
70
Fig. 2.20. Variation of cyclic volumetric strain as a function of cyclic shear strain (after Ishibashi et al., 1985)
Fig. 2.21. Change of relative density with one-way and cyclic disc shearing versus normal stress (after Yang, 2002)
Cyclic Shear
One-Way Shear
72
Fig. 2.22. Change of relative density due to cyclic disc shear with number of cycles (after Ren, 2006)
Fig. 2.23. Change of relative density due to cyclic disc shear at different depths with high of layer (after Ren, 2006)
74
Fig. 2.24. Surface settlement due to static vertical load at N = 0 to N = 40 (after Chen, 2002)
0.6
Fig. 2.25. Distribution of relative density due to cyclic torsional shearing (after Chen, 2011)
76
Fig. 2.26. Distribution of relative density in lift 1 to 4 (after Chen, 2011)
Fig. 2.27. Relationship between Relative density and qc (Jamiolkowski et al., 1985) Low compressibility High compressibility
78
Fig. 3.1. NCTU non-yielding model retaining wall and soil bin (after Chen and Fang, 2008)
1600
Fig. 3.2. Soil-Pressure Transducer (Kyowa BE-2KCM17) (after Chen, 2003)
80
Fig. 3.3. Dimensions of cyclic torsional shear compactor (after Chen, 2011)
Fig. 3.4. Cyclic torsional shear compactor (after Chen, 2011) Hoist Ring
Torque Wrench
Torque Shaft
Shear Disc
Normal Load Discs Torque Frame
82
Fig. 3.5. Bottom of shearing disc with radial fins (after Chen, 2011)
(a)
(b)
Fig. 3.6. Dimensions of a radial fin (after Chen, 2011)
84
Fig. 3.7. Bottom of shearing disc with SAFETY WALK (after Chen, 2011) Safety Walk
(a)
(b)
Fig. 3.8. Dimensions of normal loading discs (after Chen, 2011)
86
Fig. 3.9. Dimensions of torque loading frame (after Chen, 2011)
Fig. 3.10. Torque loading frame (after Chen, 2011) Hoist Ring
Hexagon cap
Torque Shaft
88
(a)
(b)
Fig. 3.11. Dimensions of torque wrench (after Chen, 2011)
(a)
(b)
Fig. 3.12. Dimensions of digital torque wrench (after Chen, 2011)
90
Fig. 3.13. Torque wrench are installed on the cyclic torsional loading frame (after Chen, 2011)
(a)
(b)
(c)
Fig. 3.14. Cone penetration facility of CYCU
Speed Control
92
(a)
(b)
Fig. 3.15. Data acquisition system Personal Computer
Labview Program
NI BNC – 2090 AD/DA Card
Dynamic Strain Amplifiers (Kyowa: DPM601A and DPM711B)
10 1 0.1 0.01 Particle Diameter (mm)
0 20 40 60 80 100
P er ce n t F in er b y W ei g h t (% )
Ottawa Silica Sand (ASTM C-778)
Fig. 4.1. Grain size distribution of Ottawa sand (after Chen, 2003)
94
Fig. 4.2. Lubrication layer on the side wall (after Chen, 2011)
1 10 100
W al l F ri ct io n A n g le ,
sw( d eg re e)
Sliding Block Test Plastic-sheet method 1 thick + 2 thin sheeting
w= 7.5
oFig. 4.3. Variation of frition Angle with normal stress (after Fang et al., 2004)
96 Unit:mm
430
120
Slot Control Handle Slot Opening
800 500
940
500
Fig. 4.4. Soil hopper (after Chen, 2011)
Slot Opening = 15 mm
Soil Control Handle
(a)
Drop Height = 1.0m
(b)
Fig. 4.5. Pluviation of Ottawa sand into soil bin (after Chen, 2011)
98
Fig. 4.6. Relationship among slot opening, drop height, and relative density (after Ho, 1999)
Fig. 4.7. Dimensions of soil density cup (after Chen, 2011)
100
Fig. 4.8. Soil density cup
Unit : mm
Fig. 4.9. Soil density cups buried at different elevations
102
Density Cup
Ottawa Sand
Left sidewall Right sidewall
Top-View
Steel Base Plate Steel Beam Steel Column
Fig. 4.10. Arrangement of soil density cups at same elevation
Fig. 4.11. Measurement of soil mass in density cup
Density
Cup Ottawa Sand
104
Fig. 4.12. Distribution of relative density with depth
Fig. 5.1. Soil storage Ottawa sand
106
Fig. 5.2. Sand hopper and electrical scale (after Chen, 2011) SandHopper
Electrical Scale
Fig. 5.3. Sand hopper lifted by overhead crane (after Chen, 2011) Overhead Crane
108
Fig. 5.4. Air-pluviation of Ottawa sand into soil bin
( a )
( b )
Fig. 5.5. Portable hanging ladders and bridge board hanging on side wall Bridge Board
Side Wall
Portable Hanging Ladder
110
Fig. 5.6. Level soil surface with a brush
(a)
(b)
Fig. 5.7. Check density cup horizontal with a bubble level Bubble Level
112
Fig. 5.8. Soil density cup and soil-pressure transducer placed on soil surface Density Cup
Soil-Pressure Transducer
Unit : mm
Fig. 5.9. Soil density cups and soil-pressure transducer buried at different elevations
114
Fig. 5.10. Grid points on soil surface
Fig. 5.11. Hoist of CTSC into the soil bin
116
Fig. 5.12. 5×5 and 4×4 loading formations of disc shearing location
Fig. 5.13. Apply vertical static load on loose sand
118
Fig. 5.14. Fixed light dot from laser distance meter Angle Steel Bar
Fixed Light Dot Laser Distance Meter
Fig. 5.15. Apply cyclic torsional shear on loose fill
120
Fig. 5.16. Shear disc at initial position = 0° (after Chen, 2011)
Ottawa Sand
Shear Disc
Laser Light Dot
Fig. 5.17. Shear disc rotated to = +5° (after Chen, 2011)
122
Fig. 5.18. Shear disc rotated to = - 5° (after Chen, 2011)
Fig. 5.19. Application of cyclic torsional shear to loose sand
124
Fig. 5.20. Compacted soil surface after 4×4 formation of cyclic torsional shear at N=5
Fig. 5.21. Compacted soil surface after 5×5 formation ofcyclic torsional shear at N=10
126
Fig. 5.22. Compacted soil surface after 4×4 formation ofcyclic torsional shear at N=20
Fig. 5.23. Soil density cups dug out of compacted soil mass
128
( a )
( b )
( c )
Fig. 5.24. Scraping of soils toward edge of density cup with a spatula
( a )
( b )
( c )
( d )
Fig. 5.25. Brush away soil particles from base plate of density cup
130
Steel Base Plate Steel Beam Steel Column
Ottawa Sand
Fig. 5.26. Arrangement of cone penetration location
(a)
(b)
Fig. 5.27. Steel beam on top of soil bin for CPT test Steel C-clamp
132
Fig. 5.28. Electric motor and movable plate fixed to the steel beam by the screws Screws
(a)
(b)
Fig. 5.29. Connect cone penetrometer with electric motor
134
Fig. 5.30. Cone penetrometer on soil surface
Fig. 6.1. Settlement measurement with laser distance meter Laser
Distance Meter
136
Fig. 6.2. Surface settlement due to static vertical loading
Fig. 6.3. Distribution of relative density due to static vertical loading (after Chen, 2011)
138
Fig. 6.4. Distribution of relative density due to static vertical loading
Unit : mm
Fig. 6.5. Locations of SPT to measure distribution of earth pressure
140
Fig. 6.6. Distribution of vertical earth pressure with depth
Fig. 6.7. Distribution of horizontal earth pressure with depth
142
Fig. 6.8. Distribution of cone resistance in soil mass
Fig. 6.9. Distribution of relative density after static load
144
Fig. 6.10. Digital torque wrench
Fig. 6.11. Torque with number of cyclic for = ±1∘, ±3∘, ±5∘, ±7∘ and ±10∘
146
Fig. 6.12. Variation of torque with shearing angle
Fig. 6.13. Determine the maximum torsional shear stress at the edge of the shearing disc due to the applied torque
148
Fig. 6.14. Maximum shear stress with shearing angle
Fig. 6.15. Settlement after cyclic torsional shearing
150
Fig. 6.16. Settlement after cyclic torsional shearing
Fig. 6.17. Distribution of relative density due to cyclic torsional shearing at = ±1°
152
Fig. 6.18. Distribution of relative density due to cyclic torsional shearing at = ±3°
Fig. 6.19. Distribution of relative density due to cyclic torsional shearing at = ±5°
154
Fig. 6.20. Distribution of relative density due to cyclic torsional shearing at = ±7°
Fig. 6.21. Distribution of relative density due to cyclic torsional shearing at = ±10°
156
Fig. 6.22. Distribution of relative density after cyclic torsional shearing
Fig. 6.23. Relative density with shearing angle
158
Fig. 6.24. Distribution of vertical earth pressure after cyclic torsional shear at = ±1°
Fig. 6.25. Distribution of vertical earth pressure after cyclic torsional shear at = ±3°
160
Fig. 6.26. Distribution of vertical earth pressure after cyclic torsional shear at = ±5°
Fig. 6.27. Distribution of vertical earth pressure after cyclic torsional shear at = ±7°
162
Fig. 6.28. Distribution of vertical earth pressure after cyclic torsional shear at =
±10°
Fig. 6.29. Distribution of vertical stress after static loading and cyclic torsional shearing
164
Fig. 6.30. Normalized vertical stress after cyclic torsional shearing
Fig. 6.31. Distribution of horizontal earth pressure after cyclic torsional shear at =
±1°
166
Fig. 6.32. Distribution of horizontal earth pressure after cyclic torsional shear at =
±3°
Fig. 6.33. Distribution of horizontal earth pressure after cyclic torsional shear at =
±5°
168
Fig. 6.34. Distribution of horizontal earth pressure after cyclic torsional shear at =
±7°
Fig. 6.35. Distribution of horizontal earth pressure after cyclic torsional shear at =
±10°
170
Fig. 6.36. Distribution of horizontal stress after static loading and cyclic torsional shearing
Fig. 6.37. Normalized horizontal stress after cyclic torsional shearing
172
Fig. 6.38. Distribution of cone resistance after cyclic torsional shear at = ±1°
Fig. 6.39. Distribution of cone resistance after cyclic torsional shear at = ±3°
174
Fig. 6.40. Distribution of cone resistance after cyclic torsional shear at = ±5°
Fig. 6.41. Distribution of cone resistance after cyclic torsional shear at = ±7°
176
Fig. 6.42. Distribution of cone resistance after cyclic torsional shear at = ±10°
Fig. 6.43. Distribution of cone resistance after cyclic torsional shearing
178
Fig. 6.44. Distribution of qc / qc,loose after cyclic torsional shearing
Fig. 6.45. Distribution of relative density after cyclic torsional shear at = ±1°
180
Fig. 6.46. Distribution of relative density after cyclic torsional shear at = ±3°
Fig. 6.47. Distribution of relative density after cyclic torsional shear at = ±5°
182
Fig. 6.48. Distribution of relative density after cyclic torsional shear at = ±7°