Compaction Rising in z-direction - Dynamic Stress Paths during Compaction

5. TEST RESULTS

5.4 Dynamic Stress Paths during Compaction

5.4.3 Compaction Rising in z-direction

The stress paths due to compaction measured with SPT5 and SPT105, SPT8 and SPT108, SPT11 and SPT111, and SPT14 and SPT114 were shown in Fig.32, 33, 34 and 35, respectively.

5.5. Comparison among Lifts and Tests

Fig. 36 (a) to (e) showed the stress paths due to the 1-second compaction at the center of Lane a for Lift 1 to Lift 5. It was observed in these figures that the shape and the size of the dynamic stress paths obtained at five different lifts were quite similar. The dynamic stress path had the shape of a comet. The comet moved between the Ko-line and Kf-line. Fig. 37 showed similar experimental results was obtained from Test 0805.

5.6. Comparison of Theoretical and Experimental Stress Paths

Fig. 38 showed the theoretical stress path of hysteretic model proposed by Broms (1971). For a soil element existed at some depth of backfill, the initial vertical stress due to the overburden soil was vi. The initial horizontal stress was σhi = Kovi, which was represented by the point A in Fig. 38. When a heavy compactor was positioned immediately above the soil element, following the Ko-line, an increase of the vertical stress resulted in an horizontal stress increase based on the assumption of no lateral yield. The stress state can be expressed as hm = K0 vm (point B). As the heavy compactor moved off the fill, a subsequent decrease in v (unloading) resulted in no

h decrease until a limitation (Kr-line) was reached (point C). The assumption was made that the maximum horizontal stress induced by compaction hm sustained until the vertical stress is reduced below a critical value at point c. After that, further v

unloading resulted in a decrease in h following the Kr-line as hf = Kr vi (point D) until the original vertical stress vi was reached. Broms (1971) assumed that Kr = 1/Ko.

The experiment stress paths due to the filling of backfill of Lift 2 (F2) and the compaction of Lift 2 (C2) were shown in Fig. 38. It is interesting to note that the starting point A and ending point D lased on Brown’s theory, was similar to the starting point A and ending point E of the stress path C2. It was indicated that compaction would result in an increase of stress only in the horizontal direction, but not in the vertical direction.

The dynamic stress path due to on-cycle of compaction at the center part of Lane A was also illustrated in Fig. 38. It was obvious that the comet-shaped dynamic stress path was quite different from the stress path proposed by Broms. It should be

mentioned that the stress path AB in Fig. 38 indicated the heavy compactor generally 5~15 ton applied a large static vertical pressure v on the surface of fill. However, stress path BC represented the removal of the heavy compactor. The mass of hand-operated square-plate compactor used in this study was only 12.1 kg (W= 119 N). The peak dynamic force applied on the surface of fill was Fx =  280 N, Fy =  1320 N , and FZ = 1690 N. The vibratory compaction was 3-dimentional and was controlled by the cyclic loading instead of the dead-load of the compactor. This was probably the main reason why the dynamic stress path due to vibratory compaction was so different from Broms’ finding.

Unit : mm

Steel Base Plate

SPT114

Fig. 16. Locations of SPT to measure distribution of earth pressure

0 5 10 15 20 25 30

Fig. 17. Distribution of vertical earth pressure with depth;

0 5 10 15 20 25 30

Horizontal Earth Pressure, h (kN/m²)

0 0.3 0.6 0.9 1.2 1.5

Elevation, z(m)

Jaky Test 0619 Test 0630 Loose Sand

(Air-Pluviation Method) Dr = 34.2 %

 kN/m³

 = 31.3^O

Fig. 18. Distribution of horizontal earth pressure

0 5 10 15 20 25 30

Vertical Earth Pressure, _v (kN/m²)

0 0.3 0.6 0.9 1.2 1.5

Elevation, z (m)

Test 0804 Test 0805 Test 0806 Test 0810 Test 0812

Test 0630 Test 0619

_v = z (6.6 kN/m³) Compacted Sand

D_r = 73.8 %

 = 16.6 kN/m³

 = 40.8^o

_v = z (5.6 kN/m³) Loose Sand

D_r = 34.2 %

 = 15.6 kN/m³

 = 31.3^o

Fig. 20. Distribution of horizontal earth pressure in compacted sand Elevation : 1.35 m

h by SPT 14 Elevation : 1.05 m

h by SPT 11 Elevation : 0.75 m

_h by SPT 8 Elevation : 0.45 m

h by SPT 5 Elevation : 0.15 m

h by SPT 2

Vertical Earth Pressure, _v(kN/m²) Horizontal Earth Pressure, h(kN/m2)

(a) (b) (c)

(e) (d)

F : Fill C : Compaction

F : Fill

C : Compaction F : Fill

C : Compaction

F : Fill

C : Compaction F : Fill

C : Compaction

Fig. 21. Static stress paths for soil element under filling and compaction of backfill (Test 0812)

0 5 10 15

Chen and Fang (2008) Test 0804 Test 0805 Test 0806 Test 0810 Test 0812

Rankine (Passive) Jaky

(c)

0 5 10 15

Chen and Fang (2008) Test 0804 Test 0805 Test 0806 Test 0810 Test 0812

Rankine (Passive) Jaky

E lev at ion , z ( m )

Chen and Fang(2008) Test 0804 Test 0805 Test 0806 Test 0810 Test 0812

Rankine (Passive) Jaky

Compacted Sand

(a)

Horizontal Earth Pressure,

0 5 10 15 Chen and Fang (2008)

Rankine (Passive)

Jaky

(d)

h,ci

Compaction-Influenced Zone

0 5 10 15 20 25 30 0

5 10 15

20 _{Test 0812}

Test 0810

Elevation : 0.15 m

_h by SPT 2

_v by SPT 102

Vertical Earth Pressure, _v(kN/m²) Horizontal Earth Pressure, h (kN/m2)

0 5 10 15 20 25 30

Elevation : 0.45 m

_h by SPT 5

Elevation : 0.75 m

_h by SPT 8

Elevation : 1.05 m

h by SPT 11

Elevation : 1.35 m

_h by SPT 14

_v by SPT 114

Fig. 22. Comparison of stress paths for soil element under filling and compaction of backfill

0 300 mm

Scale Lane f

Footboard

Model Wall Soil Pressure Transducer

(a) Compaction approaching SPT in x-direction

0 300 mm Scale Lane a Footboard

Model Wall Soil Pressure Transducer

Steel Column

Backfill

Top-View

Lane b Lane c Lane d Lane e Lane f Left wall

Right wall

Center R750 Center R375

Center Center-L375

Center L750

y x

(b) Compaction passing SPT in y-direction

1600

Unit : mm

1500

End

Steel Base Plate

Wall 45

1500 Model Wall

Sidewall Footboard

soil pressure transducer

Lane f Lift 5 Lane e Lane d Lane c Lane b

Lane a Lift 4

Lift 3 Lift 2 Lift 1

Fig. 23. Different direction for consider compaction-induced stress paths

0 5 10 15 20 25 Elevation : 0.45 m

_h by SPT 5 C2-b-Center K0

Test 0806 Elevation : 0.45 m

h by SPT 5 Elevation : 0.45 m

_h by SPT 5 Elevation : 0.45 m

h by SPT 5 Elevation : 0.45 m

_h by SPT 5 Elevation : 0.45 m

_h by SPT 5

Vertical Earth Pressure, v(kN/m²) Horizontal Earth Pressure, h(kN/m2)

(a) (b) (c)

(f) (e)

(d) F : Fill

C : Compaction

F : Fill C : Compaction

F : Fill

C : Compaction F : Fill

C : Compaction

Fig. 24. Stress paths measured at center part of the model wall by SPT5 and SPT105 due to compaction on lift 2 from Lane f to Lane a Elevation : 0.75 m

_h by SPT 8 Elevation : 0.75 m

h by SPT 8 Elevation : 0.75 m

_h by SPT 8 Elevation : 0.75 m

h by SPT 8 Elevation : 0.75 m

_h by SPT 8

Vertical Earth Pressure, _v(kN/m²) Horizontal Earth Pressure, h(kN/m2)

(a) (b) (c)

(f) (e)

(d) F : Fill

C : Compaction

F : Fill C : Compaction

F : Fill

C : Compaction F : Fill

C : Compaction

Fig. 25. Stress paths measured at center part of the model by SPT8 and SPT108wall due to compaction on lift 3 from Lane f to Lane a

0 5 10 15 20 25 Elevation : 1.05 m

h by SPT 11 Elevation : 1.05 m

h by SPT 11

Vertical Earth Pressure, v(kN/m²) Horizontal Earth Pressure, h(kN/m2)

(a) (b) (c)

(f) (e)

(d) F : Fill

C : Compaction

F : Fill C : Compaction

F : Fill

C : Compaction F : Fill

C : Compaction

Fig. 26. Stress paths measured at center part of the model wall by SPT11 and SPT111 due to compaction on lift 4 from Lane f to Lane a Elevation : 1.35 m

_h by SPT 14 Elevation : 1.35 m

h by SPT 14

_v by SPT 114

F5 C5

Vertical Earth Pressure, v(kN/m²) Horizontal Earth Pressure, h(kN/m2)

(a) (b) (c)

(f) (e)

(d) F : Fill

C : Compaction

F : Fill C : Compaction

F : Fill

C : Compaction F : Fill

C : Compaction

Fig. 27. Stress paths measured at center part of the model wall by SPT14 and SPT114 due to compaction on lift 5 from Lane f to Lane a

0 5 10 15 20 25 Elevation : 0.45 m

_h by SPT 5 Elevation : 0.45 m

_h by SPT 5

Vertical Earth Pressure, v(kN/m²) Horizontal Earth Pressure, h(kN/m2)

(a) (b) (c)

C : Compaction

F : Fill

C : Compaction F : Fill

C : Compaction

Fig. 28. Stress paths measure at SPT5 and SPT105 due to compaction on Lane (near the wall) of Lift 2 from R750 to L750 Elevation : 0.75 m

_h by SPT 8 Elevation : 0.75 m

_h by SPT 8

Vertical Earth Pressure, v(kN/m²) Horizontal Earth Pressure, h(kN/m2)

(a) (b) (c)

(d) (e) F : Fill

C : Compaction F : Fill

C : Compaction

F : Fill

C : Compaction F : Fill

C : Compaction

Fig. 29. Stress paths measure at SPT8 and SPT108 due to compaction on Lane (near the wall) of Lift 3 from R750 to L750

0 5 10 15 20 25 Elevation : 1.05 m

_h by SPT 11 Elevation : 1.05 m

h by SPT 11 Elevation : 1.05 m

h by SPT 11

Vertical Earth Pressure, v(kN/m²) Horizontal Earth Pressure, h(kN/m2)

(a) (b) (c)

(d) (e) F : Fill

C : Compaction F : Fill

C : Compaction

F : Fill

C : Compaction F : Fill

C : Compaction

Fig. 30. Stress paths measure at SPT11 and SPT111 due to compaction on Lane (near the wall) of Lift 4 from R750 to L750 Elevation : 1.35 m

h by SPT 14 Elevation : 1.35 m

_h by SPT 14 Elevation : 1.35 m

h by SPT 14 Elevation : 1.35 m

h by SPT 14

v by SPT 114

F5 C5

Vertical Earth Pressure, v(kN/m²) Horizontal Earth Pressure, h(kN/m2)

(a) (b) (c)

(e) (d)

F : Fill C : Compaction

F : Fill

C : Compaction F : Fill

C : Compaction

Fig. 31. Stress paths measure at SPT14 and SPT114 due to compaction on Lane (near the wall) of Lift 5 from R750 to L750

0 5 10 15 20 25 Elevation : 0.45 m

h by SPT 5 Elevation : 0.45 m

_h by SPT 5 Elevation : 0.45 m

h by SPT 5 C2-a-Center K₀

Test 0806 Elevation : 0.45 m

_h by SPT 5

Vertical Earth Pressure, _v(kN/m²) Horizontal Earth Pressure, h(kN/m2)

(a) (b)

(d) (c)

F : Fill

C : Compaction F : Fill

C : Compaction

Fig. 32. Stress paths measure at SPT5 and SPT105 due to compaction on center part of Lane a (near the wall) of Lift 2 to Lift 5

0 5 10 15 20 25

Test 0806 C5-a-Center K0

K_a K_p

Test 0806 Elevation : 0.75 m

_h by SPT 8 Elevation : 0.75 m

h by SPT 8

Vertical Earth Pressure, _v(kN/m²) Horizontal Earth Pressure, h(kN/m2)

(a)

F : Fill

C : Compaction F : Fill

C : Compaction

Fig. 33. Stress paths measure at SPT8 and SPT108 due to compaction on center part

0 5 10 15 20 25 Elevation : 1.05 m

_h by SPT 11 Elevation : 1.05 m

_h by SPT 11

Vertical Earth Pressure, 

(kN/m

) Hor iz ontal Ear th Pr essure, 

(kN/m

)

(b) (a)

F : Fill C : Compaction F : Fill

C : Compaction

Fig. 34. Stress paths measure at SPT11 and SPT111 due to compaction on center part of Lane a (near the wall) of Lift 4 to Lift 5

C5-a-Center K₀

K_a K_p

Test 0806 Elevation : 1.35 m

_h by SPT 14

_v by SPT 114

F5 C5

Vertical Earth Pressure, _v(kN/m²)

Horizontal Earth P ressu re, 

(k N/m

)

F : Fill

C : Compaction

Fig. 35. Stress paths measure at SPT14 and SPT114 due to compaction on center part of Lane a (near the wall) of Lift 5

0 5 10 15 20 25 Test 0806 C5-a-Center K₀

Ka Kp

Test 0806 Elevation : 1.35 m

h by SPT 14 Elevation : 1.05 m

h by SPT 11 Elevation : 0.75 m

_h by SPT 8 C2-a-Center K₀

Ka Kp

Test 0806 Elevation : 0.45 m

h by SPT 5 Elevation : 0.15 m

h by SPT 2

Vertical Earth Pressure, _v(kN/m²) Horizontal Earth Pressure, h(kN/m2)

(a) (b) (c)

(e) (d)

Fig. 36. Stress paths due to compaction at center of Lane a (near the wall) for Lift 1 to Lift 5 (Test 0806) Elevation : 1.35 m

h by SPT 14 Elevation : 1.05 m

h by SPT 11 Elevation : 0.75 m

h by SPT 8 Elevation : 0.45 m

h by SPT 5 Elevation : 0.15 m

h by SPT 2

Vertical Earth Pressure, v(kN/m²) Horizontal Earth Pressure, h(kN/m2)

(a) (b) (c)

(d) (e)

Fig. 37. Stress paths due to compaction at center of Lane a (near the wall) for Lift 1 to Lift 5 (Test 0805)

0 5 10 15 20 25 Vertical Earth Pressure, _v (kN/m²)

0 5 10 15 20

Horizantol Earth Pressure, h (kN/m2 )

Test 0806 Broms (1971)

K

-Jak y

K

Test 0806

Elevation : 0.45 m

_h by SPT 5

_v by SPT 105

F2 C2

K

C B

D E

vm

_hm

_hf

_hi

_vi

Fig. 38. Comparison of theoretical and experimental stress paths

6. CONCLUSIONS

This research studied variation of earth pressure and dynamic stress path in compacted sand. Based on the experiment results, the following conclusions were drawn.

1. For a loose backfill, the horizontal earth pressure in the soil mass was in good agreement with Jaky’s solutions. The vertical earth pressure in soil was near to the equation _v =z.

2. After compaction, the lateral stress measured near the top was almost identical to the passive earth pressure estimated with Rankine theory. The effect of vibratory compaction on the vertical pressure was insignificant.

3. After compaction, the thickness of the compaction-influenced zone rose with the elevation of the compaction surface. Below the compaction-influenced zone, the horizontal stresses converged to the earth pressure at-rest based on Jaky’s equation.

4. As the area of the compaction approached the soil pressure transducer (SPT) in x-direction (perpendicular to the wall face), the dynamic stress path became more obvious when the compactor moved to the lane near the wall.

5. As the area of compaction passed the SPT in y-direction (parallel to the wall surface), the maximum dynamic stress path was obvious when the compactor was right in front of the SPT.

6. For a SPT at a lower elevation, when the area of compaction rose with the elevation of the lift surface, the compaction-induced stress path became less significant.

7. The dynamic stress path of a soil element under vibratory compaction had the shape of a comet. The shape size of the dynamic stress paths obtained at five different lifts was quite similar. The stress paths were bounded by the at-rest Ko-line and passive Kp-line.

8. The measured dynamic stress path was quite different from the stress path proposed by Broms (1971). The stress path reported by Broms was induced by a static heavy compactor. The vibratory compactor used in this study vibrated and generated cycle force in three direction: Fx, Fy, and Fz. This was probably the main reason why the dynamic stress path due to vibratory compaction was so different from Broms’

finding.

7. RERERENCES

1. Borowicka, H., Influence of Rigidity of a Circular Foundation Slab on the Distribution of Pressures over the Contact Surface, Proc. 1^st

Int. Conf. Soil Mech.

Found. Eng., vol. 2, pp. 144-149, 1936.

2. Borowicka, H., The Distribution of Pressure under a Uniformly Loaded Elastic Strip Resting on Elastic-Isotropic Ground, 2d Cong. Int. Assoc. Bridge Struct. Eng.,

Berlin, Final report, vol. 8, no. 3, 1938.

3. Broms, B. (1971). “Lateral earth pressures due to compaction of cohesionless soils.” Proc., 4th Int. Conf. Soil Mech., Budapest, 373-384.

4. Burgess, G. P. (1999). “Performance of Two Full-scale Model Geosynthetic Reinforced Segmental Retaining Walls,” MS thesis, Royal Military College of Canada, Kingston, Ontario, 207.

5. Chang, S. Y. (2000). “Effects of Backfill Density on Active Earth Pressure.” MS thesis, Dept. of Civil Engineering, National Chiao Tung University, Hsinchu, Taiwan.

6. Chen, T. J., and Fang, Y. S, (2002). “A New Facility for Measurement of Earth Pressure At-Rest,” Geotechnical Engineering Journal, SEAGS, 3(12), 153-159.

7. Chen, T. J., (2003). “Earth Pressure Due to Vibratory Compaction”, Doctor of Philosophy Dissertation, National Chiao Tung University, Hsinchu, Taiwan.

8. Chen, T. J., and Fang, Y. S, (2008). “Earth Pressure Due to Vibratory Compaction”,

Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 134(4), 1-8.

9. D’Appolonia, D. J., Whitman, R. V., and D’Appolonia, E. (1969). “Sand Compaction with Vibratory Rollers.” Journal of the Soil Mechanics and

Foundations Division, ASCE, 95(SM1), 263-284.

10. Das, B. M., (1994), “Principal of Geotechnical Engineering.” 3^rd Edition, PWS Publishing Company, Boston.

11. Donath, A. D. (1891). “Untersuchungen veber den erddruck auf stuetzwaende.”

Zeitschrift fuer Bauwesen, Berlin.

12. Duncan, J. M., and Seed, R. B. (1986). “Compaction-induced Earth Pressures under

K -conditions.” Journal of Geotechnical Engineering, ASCE, 112(1), 1-22.

_o 13. Duncan, J. M., Williams, G. W., Sehn, A. L., and Seed, R. B. (1991). “Estimation

earth pressures due to compaction.” Journal of Geotechnical Engineering, ASCE, 117(12), 1833-1847.

14. Fang, Y. S. (1983). “Dynamic earth pressures against rotating walls.” Ph.D.

dissertation, Department of Civil Engineering, University of Washington, Seattle, Washington.

15. Fang, Y. S., Chen, T. J., Holtz, R. D., and Lee, W. F., (2004). “Reduction of

Boundary Friction in Model Tests”, Geotechnical Testing Journal, ASTM, 27(1), 1-10.

16. Filz, G. M., and Duncan J. M. “Earth Pressures due to Compaction: Comparison of Theory with Laboratory and Field Behavior.” Transportation research record, 1526, 28-37.

17. Ho, Y. C., (1999). “Effects of Backfill Compaction on Passive Earth Pressure.”

MS thesis, Dept. of Civil Engineering, National Chiao Tung University, Hsinchu, Taiwan.

18. Ingold, T. S. (1979). “Retaining wall performance during backfilling.” Journal of

the Geotechnical Engineering Division, ASCE, 105(GT5), 613-626.

19. Ingold, T. S. (1979). “The effects of compaction on retaining walls.”

Geotechnique, 29(3), 265-283.

20. Jaky, J. (1944). “The Coefficient of Earth Pressure at rest.” Journal for Society of

Hungarian Architects and Engineers, Budapest, Hungary, Oct., 355-358.

21. Jaky, J., (1948), “Pressure in Soils,” Proceedings, 2^nd

International Conference on Soil Mechanics and Foundation Engineering, 1, 103-107.

22. Johnson, A. W., and Sallberg, J. R. (1960). “Factors That Influence Field Compaction of Soil.” Highway Research Board, Bulletin No. 272.

23. 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.

24. Mayne, P. W., and Kulhawy, F. H. (1982). “

K -OCR Relationships in Soil.”

Journal of Geotechnical Engineering Division, ASCE, 108(GT6), 851-872.

25. McElroy, J. A. (1997). “Seismic Stability of Geosynthetic Reinforced Slopes: A shaking table study.” MS thesis, University of Washington, Seattle, 286.

26. Mesri, G., and Hayat, T. M. (1993). “The Coefficient of Earth Pressure at rest.”

Canadian Geotechnical Journal, 30(4), 647-666.

27. 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.

28. Rad, N. S., and Tumay, M. T. (1987). “Factors affecting sand specimen preparation by raining.“ ASTM Geotechnical Testing Journal, 10(1), 31-37.

29. 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.

30. Sowers, G. F., Robb, A. D., Mullis, C. H., and Glenn, A. J. (1957). “The Residual Lateral Pressures Produced by Compacting Soils.” Proceedings, 4^th

31. Terzaghi, K. (1934). “Large retaining-wall tests (I): Pressure of dry sand.”

Engineering News-Record, 112, 136-140.

32. Terzaghi, K. (1941). “General wedge theory of earth pressure.” ASCE

Transactions, 106, 68-80.

33. Terzaghi, K. (1943). Theoretical Soil Mechanics, Wiley, New York.

34. 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.

35. 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.

36. Vesic, A. S. (1973). “Analysis of Ultimate Loads of Shallow Foundations.”

Journal of the Soil Mechanics and Foundations Division, 99(SM1), 45-73.

37. 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.

38. 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.

可供推廣之研發成果資料表

□ 可申請專利 □ 可技術移轉

日期：100 年 8 月 1 日

國科會補助計畫

計畫名稱：震動夯實造成之土壤應力及密度變化(III) 計畫主持人：方永壽教授

計畫編號：NSC 99-2221-E-009-105- 學門領域：土木水利工程

技術/創作名稱震動夯實造成之土壤應力及密度變化發明人/創作人 ^{方永壽教授}

技術說明

中文: 本報告以實驗方法探討振動夯實造成之土壓力及其應力路徑的變化。本研究以氣乾之渥太華砂為回填土，分五層填土並且分層

夯實。夯實土層為每層0.3 m，總高度為 1.5 m。回填土初始相對密

度為34.2 %，夯實後的相對密度為 73.8 %。為了在實驗室模擬雙向

平面應變的情況，本研究採用塑膠膜潤滑層來降低砂土和填砂槽側牆間的摩擦力。本研究進行一系列實驗，探討振動夯實對砂土所產生的影響。這些影響包括夯實過程造成之土壤應力變化及其動態應

力路徑。根據實驗結果，本研究獲得以下幾項結論。(1) 於疏鬆砂土，

土體內的垂直土壓力和水平土壓力可分別以



_v  和 Jaky 公式來

 z

進行合理的估算。(2) 隨著夯實機逐漸接近土壓力計，測得之應力變化越來越明顯；在靠近擋土牆處夯實時，牆面土壓力計的應力變化是最大的。隨著覆土深度逐漸升高，深層土壓力計測得夯實造成之應力變化相當不顯著。 (3) 比較各組之應力路徑發現，夯實造成應力路徑的大小相似，應力路徑軌跡如同彗星狀。動態應力路徑都介於K0線及Kp線之間。(4) 相較於 Broms 在 1971 提出之加載-解載應

力路徑，本實驗量測出的應力路徑軌跡與 Broms 的應力路徑軌跡有

很大的差異。Broms 所提出的應力路徑是在土體上方加載一個靜態且不會振動的壓路機，而本實驗是放置一個重量較輕且具振動力的夯實機。造成差異之原因，可能是因為夯實機不只有垂直方向的施力，且造成平行牆面的水平力、及與牆表面垂直的水平力，這三個方向的動態作用力造成彗星形狀的應力軌跡。

英文：This report presents experimental data on the variation of earth pressure and dynamic stress path against a non-yielding retaining wall due to vibratory compaction. The instrumented non-yielding wall facility at National Chiao Tung University was used to investigate the effects of vibratory compaction on the change of dynamic stress in the soil mass.

在文檔中震動夯實造成之土壤應力及密度變化(III) (頁 25-0)