1、Standard Method of Test for Diamond Core Drilling for Site Investigation AASHTO Designation: T 225-16 Release: Group 3 (August 2016) American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-1b T 225-1 AASHTO Standard Method
2、 of Test for Diamond Core Drilling for Site Investigation AASHTO Designation: T 225-16 Release: Group 3 (August 2016) 1. SCOPE 1.1. This method covers a procedure for diamond core drilling designed to secure intact samples of rock and some soils that are too hard to sample by soil sampling methods.
3、This method is primarily for obtaining data for foundation and slope design and similar civil engineering purposes, rather than for mineral development and mining. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: T 206, Penetration Test and Split-Barrel Sampling of Soils T 207, Thin-Walled Tube Sampli
4、ng of Soils 2.2. ASTM Standard: D5079, Standard Practices for Preserving and Transporting Rock Core Samples 3. EQUIPMENT 3.1. A Rotary Drilling Machinecapable of providing a rotary motion and hydraulically, or mechanically, actuated feed or thrust. 3.2. A Water or Drilling Mud Pumpor air compressor
5、capable of delivering sufficient drilling fluid volume and pressure for the size of the hole to be drilled. 3.3. Core Barrelsas required. 3.3.1. A Single-Tube core barrelconsisting of a hollow tube with a threaded head at the upper end to fit the drill rod. The lower end of the barrel is fitted with
6、 a blank or set reaming shell, a core lifter, and a core bit. 3.3.2. A Double-Tube core barrel (swivel-type)having a swiveling inner barrel that is contained in the core barrel suspended on a bearing hanger. Drilling fluid is routed between the inner and outer barrels. This method improves core reco
7、very. More sophisticated double tubes are available having an inner tube that extends into the core bit, and the core lifter mounted inside the inner tube to protect cores of a soft or friable formation. 3.3.3. Single-Tube Type, WG Designconsisting of a hollow steel tube, with a head at one end thre
8、aded for drill rod, and a threaded connection for a reaming shell and core bit at the other end. A core 2016 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-1b T 225-2 AASHTO lifter, or retainer located w
9、ithin the core bit, is normal but may be omitted at the discretion of the geologist or engineer. 3.3.4. Double-Tube, Swivel-Type, WG DesignAn assembly of two concentric steel tubes joined and supported at the upper end by means of a ball or roller-bearing swivel arranged to permit rotation of the ou
10、ter tube without causing rotation of the inner tube. The upper end of the outer tube, or removable head, is threaded for drill rod. A threaded connection is provided on the lower end of the outer tube for a reaming shell and core bit. A core lifter located within the core bit is normal but may be om
11、itted at the discretion of the geologist or engineer. 3.3.5. Double-Tube, Swivel-Type, WT Designis essentially the same as the double tube, swivel-type, WG design, except that the WT design has thinner tube walls, a reduced annular area between the tubes, and takes a larger core from the same diamet
12、er bore hole. The core lifter is located within the core bit. 3.3.6. Double-Tube, Swivel-Type, WM Designis similar to the double tube, swivel-type, WG design, except that the inner tube is threaded at its lower end to receive a core lifter case that effectively extends the inner tube well into the c
13、ore bit, thus minimizing exposure of the core to the drilling fluid. A core lifter is contained within the core lifter case on the inner tube. 3.3.7. Double-Tube, Swivel-Type, Large-Diameter Designis similar to the double tube, swivel-type, WM design, with the addition of a ball valve to control flu
14、id flow in all three available sizes and the addition of a sludge barrel to catch heavy cuttings on the two larger sizes. The large-diameter design double-tube, swivel-type core barrels are available in three-core-per-hole sizes as follows: 23/4in. (69.85 mm) by 37/8in. (98.43 mm), 4 in. (101.6 mm)
15、by 51/2in. (139.7 mm), and 6 in. (152.4 mm) by 73/4in. (196.85 mm). Their use is generally reserved for very detailed investigative work or where other methods do not yield adequate recovery. 3.3.8. Double-Tube, Swivel-Type, Retrievable Inner-Tube Methodin which the core-laden inner-tube assembly is
16、 retrieved to the surface and an empty inner-tube assembly returned to the face of the borehole through the matching, large-bore drill rods without need for withdrawal and replacement of the drill rods in the borehole. This system is also known as the wire-line method. The inner-tube assembly consis
17、ts of an inner tube with removable core lifter case and core lifter at one end and a removable inner-tube head, swivel bearing, suspension adjustment, and latching device with release mechanism on the opposite end. The inner-tube latching device locks into a complementary recess in the wall of the o
18、uter tube such that the outer tube may be rotated without causing rotation of the inner tube and such that the latch may be actuated and the inner-tube assembly transported by appropriate surface control. The outer tube is threaded for the matching, large-bore drill rod and internally configured to
19、receive the inner-tube latching device at one end and threaded for a reaming shell and bit, or bit only, at the other end. 3.3.9. Triple-Tube, Swivel-Typeis similar to the double tube, swivel-type, WM design, with an inner liner into which the core is directly housed. The inner liner is commonly mad
20、e of a split steel tube, but split stainless steel tube liners and whole acrylic tube liners are also available. The inner liner is extruded hydraulically from the inner tube. Triple-tube barrel systems are available for conventional or wireline methods. Triple-tube core barrels are available with r
21、eaming shell sizes A, B, N, and larger. Set bit core diameters are slightly smaller compared to WM set bit core diameter sizes to account for the inner liner thickness. 3.3.10. Longitudinally Split Inner TubesAs opposed to conventional cylindrical inner tubes, these allow inspection of, and access t
22、o, the core by simply removing one of the two halves. They are not standardized but are available for most core barrels, including many of the retrievable inner-tube types. 2016 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation
23、 of applicable law.TS-1b T 225-3 AASHTO 3.3.11. The size and design nomenclature shall be in accordance with the standards adopted by the Diamond Core Drill Manufacturers Association. 3.4. Core BitsThe core bits shall be set with diamonds, tungsten carbide, or similar hard materials appropriate to t
24、he hardness of the materials being drilled and shall be furnished in X- or M-design or equivalent as required. The sizes of the core barrels and bits shall be as given in Table 1. Table 1Sizes of Core Barrelsa Hole, Diameter Core, Diameter Size in. mm in. mm EWX, EWM 1.5 38.1 0.812 20.6 AWX, AWM 1.9
25、57 49.2 1.375 30.2 BWX, BWM 2.375 60.3 1.625 41.3 NWX, NWM 3 76.2 2.125 54.0 23/4by 37/8in. (69.9 by 98.4 mm) 3.875 98.4 2.687 68.3 4 by 51/2in. (102 by 140 mm) 5.5 140 3.937 100 6 by 73/4in. (152 by 197 mm) 7.75 197 5.937 151 a As standardized by the Diamond Core Drill Manufacturers Association, Bu
26、lletin No. 2. Other sizes may be specified, but should be so noted. 3.5. Drive Pipe or CasingStandard weight or extra heavy pipe, as required by the nature of overburden or the drilling method, shall be furnished where necessary for driving through soils to bedrock. The casing or pipe shall have an
27、inside diameter of sufficient size to accommodate the largest size core barrel to be employed. The inside of the casing or pipe shall be free of burrs and obstructions. 3.6. Auxiliary CasingWhen it is necessary to case through formations already penetrated by the drill or when no drive casing has be
28、en employed, casing shall be provided with an outside diameter that will fit inside the hole and an inside diameter that will permit the use of the next smaller bit and core barrels. Standard sizes of casing are given in Table 2. Table 2Standard Sizes of Casing Outside Diameter Inside Diameter Will
29、Fit Hole Drilled by: Size in. mm in. mm EX 1.8125 46 1.5 38.1 AWX, AWM AX 2.25 57.2 1.906 48.4 BWX, BWM BX 2.875 73.0 2.187 60.3 NWX, NWM NX 3.5 88.9 3.0 76.2 23/4by 37/8in.(69.9 by 98.4 mm) 3.7. Drill RodsThe drill rods shall have an inside diameter that will permit the flow of drilling fluid throu
30、gh the rods in a quantity sufficient to provide an upward velocity of the fluid between the rod and the hole wall that will remove the cuttings effectively. 3.8. Auxiliary EquipmentAuxiliary equipment shall be furnished as required by the work including roller bits, fishtail bits, wrenches, equipmen
31、t for mixing the drilling mud, hand tools, safety equipment, etc. 3.9. Core BoxesCore boxes of wood or other durable material shall be provided for protection, transport, and storage of the cores. The boxes shall be provided with longitudinal spacers that will 2016 by the American Association of Sta
32、te Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-1b T 225-4 AASHTO separate the core into compartments. Small blocks that fit snugly between the spacers shall be provided to secure core in place and/or fill space if the material recovered
33、is insufficient to completely fill the box. The top of the core length, which corresponds to the shallowest depth, should be placed at one corner of the box and the core placed progressing downward in a continuous manner to the deepest depth, through the compartments toward the opposite corner. The
34、top and bottom of the core length and each run shall be clearly indicated on the longitudinal spacers or blocks with waterproof marker. The top and bottom of the core length shall also be clearly indicated on the box cover, at the corresponding corners along with the core depths. Additional guidance
35、 regarding labeling and use of core boxes can be found in ASTM D5079. 4. PROCEDURE 4.1. When formations are encountered that are too hard to be sampled by soil sampling methods, the core drilling procedure shall be used. A penetration of 1 in. (25 mm) or less for 50 blows (Notes 1 and 2) according t
36、o T 206 shall be considered as indicating that soil sampling methods are not applicable. Note 1When the subsurface investigation requires a sample for testing and identification for material that has a penetration-resistance between N = 100 specified in T 206 and 50 blows per inch, coring may be req
37、uired. Materials such as very stiff clay or weathered shale bedrock can be sampled using core barrels such as the Denison-type Double-Tube Core Barrel. The sampling can be enhanced by the use of air for the drilling medium and the use of bits with hardfaced steel teeth. Note 2The limit of 50 blows p
38、er inch (25.4 mm) may be increased if the core recoveries prove to be small and samples can be secured by the soil sampling method. 4.2. Firmly seat the casing on bedrock or hard material to prevent loose materials from entering the hole and to prevent the loss of drilling fluid. Level the surface o
39、f the rock or hard material when necessary by the use of a fishtail or other bits. If an open drill hole can be maintained without casing, the casing may be omitted. Bentonite mud is often effective in maintaining an open hole without the use of casing. 4.3. Begin the core drilling using the NWX or
40、NWM double tube swivel-core barrel. The first core run will usually be 5 ft (1.52 m) because of nonuniform conditions at the soil rock contact (Note 3). The NWM barrel should be inspected prior to lowering into the hole to ensure that the swivel is in good working order and rotating freely. The clea
41、rance between the inner barrel, when incorporated in the barrel, and the bit should be checked and adjusted if necessary to ensure that the space between the bit and the inner barrel is sufficient so as not to restrict the flow of drilling fluid. Either type barrel should be inspected for dents or b
42、ends that impair rock recovery. The barrel should also be checked for material left in the barrel from previous drilling to ensure the barrel is clean and unobstructed. The core retainer should be inspected, and if worn excessively or damaged, it should be replaced. The choice of bit setting shall b
43、e consistent with the type of material to be drilled. Extreme care should be exercised to avoid dropping foreign material into the hole. Should an object be dropped into the hole and not be recoverable, the hole may have to be abandoned. Inspect all drill rods to be used for straightness. If any rod
44、s display bends when rolled over a flat surface, they should not be used. Note 3In soft materials, a larger starting size or triple-tube system may be specified; where local experience indicates satisfactory core recovery or where hard, sound materials are anticipated, a smaller size or the single-t
45、ube type may be specified in place of the NWX or NWM tube, and longer runs may be drilled. Single-tube type barrel should only be used where hard, sound materials are anticipated, and where the consequence of core quality or the presence of natural discontinuities would not adversely impact the desi
46、gn or construction of the facility for which the subsurface investigation is being conducted. 4.4. Lower the barrel into the hole, using care to set the barrel on the formation to be drilled gently to prevent damage to the bit or buckling of the barrel. Measurement of barrel and rods to be used is 2
47、016 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-1b T 225-5 AASHTO essential; measurement shall be to the nearest 0.1 ft (30.5 mm). Log the depth when the barrel makes contact with the bottom of the ho
48、le. If the depth is more than 0.1 ft (30.5 mm) less than the depth logged from the previous run, there is probably loose material or core in the hole. Connect the drill chuck to the string of tools and connect the drilling fluid supply line. Prior to rotating, lift the string of tools slightly and s
49、tart the circulation of the drilling fluid. Allow the fluid to circulate until a full-flow condition is reached. Lower the tools slowly to the bottom and seat the bit by slowly starting the rotation and slowly increasing the vertical pressure, maintaining full flow of the drilling fluid. When the bit is seated, adjust the vertical pressure and the rotation to achieve proper penetration in accordance with the formation being drilled (Note 4). Log the depth where the coring began to the nearest 0.1 ft (30.5 mm). If the flow of the drilling fluid is blocked
