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Section 03 - Part 2 - Boreholes

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  i  I  MP E R I  A L T R A D I  N  G &  C  ON T R A  C T I  N  G C  O.W.L .L  (  I  T  C  C  )   QCS 2010 Section 3 Part 2 Boreholes Page 1 2.   BOREHOLES .............................................................................................................2   2.1   GENERAL ...................................................................................................................2   2.1.1   Scope  2   2.1.2   References  2   2.2   BOREHOLES GENERALLY ....................................................................................2   2.2.1   Method and Diameter   2   2.2.2    Addition of Water to the Borehole  2   2.2.3   Backfilling  2   2.3   PERCUSSION BORING  ..........................................................................................3   2.3.1   Hard Stratum or Obstruction in Percussion Boring  3   2.4    AUGER BORING .......................................................................................................3   2.4.1   Hand Auger   3   2.4.2   Continuous Flight Auger Boring  3   2.4.3   Hollow Stem Flight Auger   3   2.5   ROTARY DRILLING ..................................................................................................3   2.5.1   General  3   2.5.2   Drilling Fluid  3   2.5.3   Rotary Drilling with Core Recovery  3   2.5.4   Rotary Drilling without Core Recovery  5   2.5.5   Backfilling  5   2.5.6   Photographs  5   2.6   BOREHOLES OVERWATER ..................................................................................6   QCS 2010    i  I  MP E R I  A L T R A D I  N  G &  C  ON T R A  C T I  N  G C  O.W.L .L  (  I  T  C  C  )   QCS 2010 Section 3 Part 2 Boreholes Page 2 2. BOREHOLES 2.1 GENERAL 2.1.1 Scope 1 Advancement of boreholes by percussion boring, auger boring, and rotary drilling in soils. 2 Related Sections and Parts are as follows: This Section Part 1, General Section 4, Piling Section 6, Roadworks Section 8, Sewerage Section 12, Earthworks Related to Buildings 2.1.2 References 1 The following standards and other documents are referred to in this Part:   BS 5930, Code of practice for site investigations.   Engineering Group of the Geological Society Working Party Report  The logging of rock cores for engineering purposes  (1970).   2.2 BOREHOLES GENERALLY 2.2.1 Method and Diameter 1 The method of advancement and the diameter of a borehole shall be such that the boring can be completed and logged to the designated depth, and samples of the designated diameter can be obtained, in-situ testing carried out and instrumentation installed. 2 The following methods may be employed for advancement of a borehole unless otherwise designated: (a) Percussion boring. (b) Auger boring (If hollow stem augering is proposed, the Contractor shall satisfy the Employer that the SPT values obtained are not effected by disturbance of the soil by the auger head, or the presence of material within the hollow stem.). (c) Rotary drilling. 2.2.2 Addition of Water to the Borehole 1 Jetting with water shall not be used to assist the advance of the borehole, except where approved by the Engineer. Where the borehole penetrates below the water table and disturbance of the soils is likely, a positive hydraulic head shall be maintained in the borehole. 2.2.3 Backfilling 1 The Contractor shall backfill boreholes in such a manner as to minimise subsequent depression at the ground surface due to settlement of the backfill. In some circumstances, grout or special infilling may be required by the Engineer. Where artesian or other water conditions make normal backfilling impracticable, the Contractor shall consult and agree with the Engineer a procedure for sealing the borehole. QCS 2010    i  I  MP E R I  A L T R A D I  N  G &  C  ON T R A  C T I  N  G C  O.W.L .L  (  I  T  C  C  )   QCS 2010 Section 3 Part 2 Boreholes Page 3 2.3 PERCUSSION BORING 2.3.1 Hard Stratum or Obstruction in Percussion Boring 1 In a borehole where percussion boring is employed and a hard stratum or obstruction is encountered, the Contractor shall employ chiselling techniques for a period of up to 1 h. Should this not penetrate through the hard stratum or obstruction the Contractor shall inform the Engineer, who may instruct the use of one or more of the following: (a) continuation of chiselling techniques (b) rotary or other approved drilling until the stratum is penetrated (c) abandonment of the borehole. 2.4 AUGER BORING 2.4.1 Hand Auger 1 Hand auger boring may be appropriate in suitable self-supporting strata. 2.4.2 Continuous Flight Auger Boring 1 Where continuous flight auger boring is used, it shall be carried out under the full-time supervision of a person meeting the requirements of Part 1 Clause 1.5 Paragraph 5 Item (c) who shall produce, as boring proceeds, a record of the material and groundwater encountered. 2.4.3 Hollow Stem Flight Auger 1 Where hollow stem flight auger boring is used, the equipment used shall be such as to bore and recover samples as designated. Sampling shall be carried out through the hollow stem. 2.5 ROTARY DRILLING 2.5.1 General 1 Rotary drilling may be required for the recovery of cores, or for the advancement of a hole in rock, with or without core recovery. 2.5.2 Drilling Fluid 1 The drilling fluid shall normally be clean water, air or air mist. However, with the approval of the Engineer, drilling muds, additives or foam may be used. 2.5.3 Rotary Drilling with Core Recovery 1 Unless otherwise designated rotary core drilling shall be carried out by a double or triple tube coring system incorporating a removable inner liner. The triple tube system may be affected by use of a double tube barrel with an approved semi-rigid liner. 2 Rotary core drilling shall produce cores of not less than the designated diameter throughout the core length. Care shall be exercised in the drilling so as to optimise core recovery. 3 The first drill run in each hole shall not exceed 1m in length. Subsequent drill runs shall not normally exceed 3 m in length and the core barrel shall be removed from the drill hole as often as is required to obtain the best possible core recovery. The Engineer may designate in-situ testing between drill runs. QCS 2010    i  I  MP E R I  A L T R A D I  N  G &  C  ON T R A  C T I  N  G C  O.W.L .L  (  I  T  C  C  )   QCS 2010 Section 3 Part 2 Boreholes Page 4 4 Removal of cores and labelling of liners shall be carried out as follows: (a) All operations entailed in recovering the cores from the ground after completion of drilling shall be carried out in a manner such as to minimise disturbance to the cores. (b) Core barrels shall be held horizontally while the innermost liner containing the core is removed without vibration and in a manner to prevent disturbance to the core. The core should be rigidly supported at all times while it is being extruded and during subsequent handling, and the liner containing the core must not be allowed to flex (c) Immediately after removing the liner the top and bottom shall be marked in indelible ink. The ends of liners shall be capped and sealed using adhesive tape. Liners shall be cut to the length of the enclosed core. (d) Where the length of core recovered from any single core run is such that it cannot be accommodated in one channel of the core box, the liner shall be cut to coincide, if possible, with existing fractures. The liner either side of the cut shall be marked 'cut' and the ends capped as above.   (e) Each section of liner shall be marked with the contract title, exploratory hole reference number, date and the depths of the top and bottom of the drill run. (f) Core obtained without a liner and that from within the core catcher but not inside the liner shall be wrapped in two layers of plastic cling film and labelled to indicate the depth and exploratory hole reference number. 5 Core boxes, packing, labelling, storing shall be carried out as follows: (a) Core boxes shall be soundly constructed and fitted with stout carrying handles, fastenings and hinged lids. The total weight of the cores and box shall together not exceed 60 kg.   (b) Cores shall be rigidly and securely packed at the site of drilling and during all subsequent handling and storage the cores shall remain packed unless required for examination or testing. Cores shall be placed in the box, in their liners where used, with the shallowest core to the top left hand corner, the top being considered adjacent to the hinged section. Cores from the core catcher shall also be placed in the core boxes at the correct relative depth. (c) Depth shall be indicated on the core box by durable markers at the beginning and end of each drill run. Rigid core spacers shall be used to indicate missing lengths. The contract title, exploratory hole reference number and the depth of coring contained in each bore shall be clearly indicated in indelible ink inside, on top and on the right-hand end of the box and on the inside of the box lid. (d) Core boxes containing core shall be kept horizontal and moved and handled with care at all times. Cores shall be protected from direct sunlight. At the end of each day's work, core boxes shall be stored secure from interference and protected from the weather. 6 Cores shall be prepared for examination as follows: (a) Cores shall be prepared for examination by the removal of sealing materials and splitting of liners in such a way as not to damage the cores. Plastic liners shall be cut lengthways such that at least half the core circumference is exposed. (b) Before examination of the core, the Contractor shall photograph the cores. The time between beginning preparation and the examination of the prepared and photographed cores shall be minimised to prevent loss of moisture from the core samples. QCS 2010  
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