1. Pertemuan 10 Penurunan Pondasi Dangkal
Matakuliah : S2094 / Rekayasa Pondasi
Tahun : 2005
Versi : 1.1
Pertemuan 10 Penurunan Pondasi Dangkal

2. Settlement Analysis Based on Laboratory Tests
Approach used when good quality “undisturbed” samples can be obtained from soil
Perform consolidation test
Obtain Cc, Cr , e0, and ´m
Perform settlement analysis

3. Two Methods of Analysis
Classical Method
Based on Terzaghi’s Theory
One dimensional compression
Skempton and Bjerrum Method
Considers distortion settlement
Uses an adjustment factor for 3D compression

4. Classical Method; Foundation Rigidity Factor

5. Classical Method

6. Thickness of Soil Sub-layers

7. Settlement Predictions N.C. Clays

8. Settlement Predictions O.C. Clays…… Case I

9. Settlement Predictions O.C. Clays…… Case II

10. Skempton & Bjerrum Method
Settlement,
Distortion Settlement (d)
Consolidation Settlement (c)

11. Distortion Settlement

12. 3D Adjustment Factor, 

13. Influence Factors, I1 and I2

14. I2

15. Example 7.3

16. Example 7.4

17. Settlement Analysis based on In-Situ Tests
Techniques for estimating settlements in sands are nearly always based on in-situ test results
In sands, settlement analysis is not performed based on consolidation analysis
Instead, we use Equivalent Modulus of Elasticity, Es

18. Es from SPT Data (Table 7.4)

19. Es from CPT Data (Table 7.3)

21. Schmertmann’s Method C1 = depth factor = C2 = Secondary creep factor =
C3 = Shape factor =

23. Strain Influence Factor

24. Simplified Schmertmann Method
When Es is uniform with depth over the depth of influence
For square/circular footings:
For continuous footings:

25. Settlements in Stratified Soils
When the soil profile primarily consists of clays and silts – use procedures described in Section 7.4 to estimate settlement
For clays/silts use laboratory consolidation tests to determine Cc/(1+e0) and Cr/(1+e0)
For sands use Cc/(1+e0) or Cr/(1+e0) from Table 3.7

26. Settlements in Stratified Soils
When the soil profile primarily consists of sands and silts – estimate settlement based on Schmertmann Method
Use in-situ test data to determine Es for sand
Use following equation to determine Es for clays or

27. Settlements in Stratified Soils
Alternative Approach
Conduct separate analysis for clays/silts and sands
Add the computed settlements

28. Differential Settlement
Total Settlement, 
Differential Settlement, D
Rotation, 

29. Differential Settlement
Variations in Soil Profile
Variations in Structural Loads
Design Controlled by Bearing Capacity
Construction Tolerances

30. Computing Differential Settlement
Consider best case/worst case scenarios
Use D/ ratios
Clayey Soils…. Figure 7.20
Sands …. Figure 7.21

31. Total and Differential Settlement for Clays

32. Total and Differential Settlement for Sands

33. Design values of D/ Ratios

34. Rate of Settlement
In saturated soils rate of settlement depends largely on how fast the water drains away
In Clays rates of settlement are slower than in sands
Consolidation theory allows you to calculate rate of settlement (Chapters 19 and 20)
Rate of settlement in sands vary depending upon the pattern of loading

35. How Accurate are our Settlement Predictions?

36. Computer Software SCHMERT (schmertmann.xls)