1. Matakuliah: S2094 / Rekayasa Pondasi Tahun: 2005 Versi: 1.1 Pertemuan 03 Penyelidikan Tanah Media referensi video : DrillingAndSampling.wmv minicone.wmv

2. Site Exploration and Characterization “ Subsurface material properties cannot be specified; they must be deduced through exploration.” Charles Dowding (1979)

3. Objectives zDetermine location and thickness of soil and rock strata (subsurface soil profile) zDetermine location of groundwater table zRecover samples for laboratory testing zConduct lab and/or field testing zIdentify special problems and concerns

7. zProject Assessment zLiterature Search zField Reconnaissance zSubsurface Drilling and Sampling zLaboratory Testing of Soil Samples Site Exploration; General Strategy

8. zType, location and approximate dimensions of the proposed development zExisting topography and any proposed grading zAny previous developments Project Assessment

9. zGeologic Maps zSoil Survey Reports zGeotechnical Reports zHistoric Groundwater Data Literature Search

10. zGeologic Maps

11. zConventional Aerial Photographs yGeologic features (landslides, faults), topography, drainage patterns ySite history zInfrared Aerial Photographs ySprings, seepage zones yUseful in slope stability investigations Remote Sensing

12. zAny previous developments, grading etc. zSite topography, any signs of slope instability (landslides, soil creep) zSite drainage conditions zRock outcrops zSite access Field Reconnaissance

13. Field Exploration zSite Boring Layout zTest Borings or Test Pits? yIt depends on the type of materials, and what you want to know. zNumber and Frequency of Borings zDepth, Sampling Methods and Field Testing

14. Field Exploration

15. III. Subsurface Exploration/Sampling z Borehole Spacing ySite conditions/uniformity ytype of structure (bridge, building, landfill) ytypically one borehole/2500 ft 2 yAlso see Table 4.1 (p.108) zBorehole Depths yMagnitude of loading/soil conditions yAlso see Table 4.3 (p.109)

16. How Many Borings?

17. How Deep?

18. Look Up and Live! zSafety Awareness zRegular Emphasis

19. zSubsurface Drilling yAuger Drilling xSolid Stem Auger xHollow Stem Auger yRotary Drilling yBucket Auger yPercussion (or Cable Tool) Drilling Drilling and Sampling of Soils

20. Auger Drilling

21. zHollow Stem Auger yCasing with outer spiral yInner rod with plug/or pilot assembly yFor sampling, remove pilot assembly and insert sampler yTypically 5ft sections, keyed, box & pin connections yMaximum depth 60-150ft Auger Drilling

22. Hollow-Stem Augers

23. Air or Mud Rotary Drilling  http://www.redi-drill.com/ms- index.htm

24. zBit at the end of drill rod rotated and advanced zSoil/rock cuttings removed by circulating drilling fluid zCommon drilling fluid; bentonite in water with slurry density 68-72pcf zAir may be used as drilling fluid Rotary Drilling

25. zNot common in US in geotechnical explorations zHeavy impact drilling tools lifted and dropped zImpact loosens soil and rock zCuttings removed with a bailer zSlow process; Used in environmental explorations where drilling fluid is not permitted Cable Tool Drilling

26. Rock Drilling, Coring, Augering zhttp://www.globaldril sup.com/cat- index.html

27. Soil and Rock Sampling zDisturbed samples yIn-place structure is not preserved yOkay for determination of soil index properties z“…Estimating the nature of the formation from the cuttings is like identifying the cow from the hamburgers.” G.F. Sowers

28. Soil and Rock Sampling zUndisturbed samples yMinimizes effects from potential disturbance yNeeded for determination of in-situ density, in-situ permeability, soil shear strength and compressibility

29. Soil Samplers zStandard Split Spoon Samplers zShelby Tube Samplers zPiston Samplers zHeavy Wall Samplers

30. Standard Split Spoon Samplers zThick wall (0.25in) cylinder zSampling tube is split along the length zHammered into the ground

31. Shelby Tube (Thin-wall) Samplers zThin wall (1/16in) sampling tube zSampler pushed into the ground hydraulically zSample extruded from tube

32. Piston Samplers zMinimizes sample disturbance caused by back-pressure

33. Heavy-Wall Samplers zThicker walls provide better strength & durability zHowever, it creates more disturbance zSampler pounded into the ground

34. Groundwater Monitoring zGroundwater level must be determined during geotechnical investigation zCan be accomplished by leaving selected soil borings open

35. In-situ Testing zWhen it is difficult to obtain “undisturbed” samples zCohesionless soils, Sensitive clays zIn-situ Test Methods yStandard Penetration Test (SPT) yCone Penetration Test (CPT) yPressuremeter Test yFlat Plate Dilatometer Test

36. Standard Penetration Test (SPT) z140 lb (63.5 kg) Hammer z30in (76 cm) free fall zDrive sampler over 18 inches zRecord no. of blows per each 6 inch penetration zSPT blow count=blows for 2 nd 6 inch penetration + blows for 3 rd 6inch penetration

37. Standard Penetration Test (SPT)

39. Types of SPT Hammers

40. Corrections to SPT blow Counts zFactors affecting SPT blow count: zHammer Efficiency (See Table 4.3) zBorehole diameter (See Table 4.4) zType of sampler (See Table 4.4) zRod length (See Table 4.4)

41. SPT Correction Factors

42. SPT Overburden Correction

43. Use of SPT Data zTo Determine Relative Density, D r yFrom AASHTO Chart yFrom Eq. (4.3) p.122 zTo determine  yFrom Figure 4.11 (p.123) zTo determine C yFrom AASHTO Chart