Karotlu Sondaj
Eritmeli Sondaj
SONDAJ EKİPMANI
Sondaj kuyusunun gerekli derinliğinde ve numune alma kategorilerinde, gerekli numune alma ve sondaj kuyusu deneylerini gerçekleştirmek için tij, muhafaza borusu, karotiyer ve matkapları dayanıklılık, güç ve donanım açısından uygun olan sondaj makineleri seçilmelidir (TS EN ISO 22475-1). Sondajın birçok tipi bulunmaktadır (Tablo 2). Bunlar;
- Yıkamalı (Rotary)
- Burgulu (Auger)
- Darbeli (Percussion)
- Titreşimli (Sonic)
olarak kategorize edilebilir. Sondajlarda açılan kuyunun stabilizasyonu, gerilme boşalması meydana gelmemesi, örselenmenin azalması ve sağlıklı numune almak için çok önemlidir. Kullanılan teknikler şu şekilde sıralanabilir:
- Su
- Sondaj sıvısı (polimer, mineral katkılı)
- Muhafaza borusu
- Enjeksiyon
- Dondurmak
Türkiye’de zemin araştırma sondajlarının neredeyse tamamına yakını, yıkamalı olarak (genellikle sirkülasyon sıvısı olarak su ile, özel durumlarda ise bentonit veya polimer ile), Tablo 2 - Satır 2‘de belirtilen döner (rotary) karotlu sondaj yöntemi ile yapılırken zemin etüdü maksatlı yapılan sondajlarda genellikle karotiyerler kullanılmaktadır (Tablo 3).
The drilling will be performed with Drilling Rigs which are suitable for Rotary Core (RC) and Rotary Open Hole (RO) "Destructive Drilling" with Commachio MC405 .
Şekil 2 Sondaj makinası genel görünüş
Diesel powered or hydraulically powered triplex pump will be used with 80-180 lt/min water flow and max. 35 bar capacity.
When manoeuvring by the mast of the drilling rig will be lowered to the horizontal or near horizontal position (depending on SPT Equipment position). The unit is capable of scaling slopes to a maximum of 1 in 3 under normal circumstances.
Before positioning the rig the ground will be levelled and supported for the drilling rig positioning over the assigned bore hole.
There will be a danger zone around the rig during operation. This extends to 3 meters in all directions out from the rig. Once the rig has been positioned, this zone will be enforced as it is important to make sure the danger zone is clear
Şekil 3 Sondaj makinası tipik kurulumu ve çalışma alanı
Unsafe working conditions will not be allowed. The work will be stopped if there is heavy rain or lightning, which could lead to such conditions. A drip tray and oil spill kit will be stored with the rig in case of any accidental spillage of oil, diesel or other fluids. Typical Location Plan for Containers are presented in Şekil 3.
Crane will be in use during mobilization to the job site for lifting the water tank and containers. There are no Overhead Power Lines (OHPL) interfering with the lifting operation.
The circulation fluid will be stored at isolated circulation pit and disposed to the existing channels if agreed with the landowner, otherwise stored temporarily at water tanks and disposed with vacuum tracks to the municipal water treatment plant.
Tablo 3. Türkiye’de Genellikle Kullanılan Karotiyer Tipleri, Geometrik Özellikleri ve Karot Çapları
Tablo 4. Çelik halatlı (wireline) geoteknik etüt karotiyeri (3 Tüplü) – (TS EN ISO 22475-1, Çizelge-C.13)
Türkiye’deki mevcut tüp çapları 30-80mm arasında olması sebebiyle TS EN ISO 22475-1 uyarınca “Küçük Çaplı Sondaj” olarak tanımlanmaktadır. Bu şekilde genellikle Tek Tüplü (T) karotiyerden Kategori “B” ve Kalite Sınıfı “4”, Çift Tüplü karotiyerden ise Kategori “B” ve Kalite Sınıfı “3” Sınıf numune elde edilebilmektedir. Bu numuneler üzerinde TS EN ISO 22475-1 uyarınca Tablo 5’te belirtilen sınırlı indeks laboratuvar deneyleri yapılabilmektedir.
Özel bazı projelerde Geoteknik Arazi Karakterizasyonu maksadı ile TS EN ISO 22475-1 uyarınca “Çelik Halatlı (Wireline) Geoteknik Etüd Karotiyeri” olarak isimlendirilen P ve S ebatlarında 3 Tüplü Karotiyerler kullanılmaktadır (Tablo 4, Şekil 2).
GEOBOR-S (tripleks) karotiyer ile elde edilen karot çapı 102mm’dir ve Geoteknik Arazi Karakterizasyonu açısından tavsiye edilen ölçüdür. Bu şekilde elde edilen karottan Kategori “A”, Kalite Sınıfı “1” numune alınarak (Tablo 2). TS EN ISO 22475-1 uyarınca Tablo 5’te belirtilen bütün laboratuvar deneyleri (indeks ve mukavemet deneyleri dahil olmak üzere) yapılabilmektedir.
Şekil 2 GEOBOR-S (3 Tüplü Wireline) Karotiyer İç ve Dış Tüp Şematik Çizim ve Görünümü
(TS EN ISO 22475-1, Şekil C.8)
Rotari Delgi
Inspection pits will be dug till 1.2m depth at all exploratory hole locations. Rotary drilling will start from ground level in soil or rock. Drilling may be instructed in low strength or fragmented zones of rock lying either within or outside the rock formation.
Rotary Open Hole (Destructive Drilling)- RO
Drilling shall normally be carried out with clay bit or tri-cone bit which shall be suitable for the ground conditions encountered and for the requirements of the investigation. Openhole drilling shall be carried out with a wet flushing rotary drilling system for instrument installation. Boreholes will be performed with GEOBOR-S wireline core barrel with Method 6 (Destructive Drilling) and cased with SW where required to prevent water ingress and caving ground and that the casing shall be installed at 1.5m or 3m intervals (depending on the run length). With the Engineer's consent other methods, such as grouting or destructive drilling with rods may be used.
Şekil 4 General View from the Tri-Cone Bit and Clay Bit for Destructive Drilling
Following the drill rods are removed from the borehole in open-hole drilling the depth of the borehole shall be measured to an accuracy of 10mm using a method agreed with the Engineer. The measurement shall be recorded on the daily journal and used to calculate the depth of the borehole, caving or other material present at the base of the borehole by comparison with the borehole depth determined from the length of equipment down the borehole at the end of the drill run.
Şekil 5 GEOBOR-S Metod-6 Eritmeli Sondaj Karotiyer Şematik Göterimi
Rotary Core Drilling (Continues Core Drilling)-RC
Drilling shall normally be carried out with diamond-tipped or tungsten carbide-tipped bits which shall be suitable for the ground conditions encountered and for the requirements of the investigation. Rotary core drilling shall be carried out with a drilling system in which the core barrel is lined with a one-piece cylindrical semi-rigid transparent plastic liner of 3mm wall thickness shall yield 76mm minimum diameter cores (Figure 10).
Figure 10 A Typical View from Triplex Core Barrel with Plastic Liner and Drilling Bits
The drilling will be flushed with water + polymer mud (non-Toxic or biodegradable unless agreed otherwise with the Engineer). Aus-Trol Viscofier and CR-650 Core Recovery Polymer or equivalent will be used as additives to circulation fluid as per Specification (Appendix 2) for effective - improved core recovery in most difficult drilling conditions.
The percentage return and colour of the flush medium shall be recorded for each drill run. If the quantity of solid material discharged from the borehole exceeds that which can be attributed to the volume of cuttings, drilling shall cease and the fact shall be reported to the Engineer immediately.
In the absence of any other directive or requirement of the Engineer, the type and state of the drill bit and core barrel, feed rates, drilling flush medium and management of the equipment will be such that total core recovery (TCR) of not less than 97% in any single run is obtained.
Optionally, Drilling parameter recording (or instant logging) consists in measuring and recording one or more physical magnitudes depending on depth and during the drilling operation. Variations depend on the ground encountered: penetration rate, torque, water pressure etc. (Figure 11). These lithological parameters are supplemented by parameters that describe the drilling operation such as;
- Depth,
- Drilling rate,
- Rotation Speed,
- Torque,
- Thrust pressure,
- Retaining pressure,
- Injection fluid flow rate and pressure.
Figure 11 A schematic view of Drilling Parameter Measurement System.
Figure 12 A schematic view of T6 Conventional Core Barrels and Triplex PVC Tube (from Technidrill Cataloque).
Figure 13 A schematic view of P-WL3 Geotechnical Wire Line Core Barrels with Semin Rigid Tube (from Technidrill Cataloque).
All boreholes will be drilled using a T6 Conventional core barrel systems or Geotechnical Wire Line Core Barrel System. To improve recovery of intact cores in soft, non-homogeneous or fractured formations, the triplex inner tubes in transparent plastic material will be used (101mm to 131mm Double Tube Core Barrel Systems could be transformed to Triplex Tube version or P-WL3 Wire Line Core Barrel with Liner Tube) with the face discharge core bits. The drilling mud ejected through the holes on the surface of the bit reduces considerably erosion of the cores. The transparent plastic inner tube not in friction with the inner tube, is removed easily, decreasing the time of core extraction. To transform the double tube core barrel into the triple tube version, only the core lifter, core lifter case and drill bit will be replaced.
Continuous samples will be recovered in core runs nominally 1.50m or 3.00m long. For Triplex Plastic Liner Tube Version Core runs will be stored in airtight plastic liners in wooden or plastic core boxes. The liners will be split in the laboratory or logging container. Undisturbed core sub-samples (CSS) which are suitable for tri-axial testing will be obtained from core runs as specified by the Engineer. Core sub-samples will be removed from the core liner and sealed with three alternating layers of cling film (stretch film) and paraffin wax and finally wrapped in tinfoil (aluminium foil) with the top of the sample clearly marked. The samples shall be stored in hard boxes prior to testing.
The first and second drill run in each borehole will not exceed 1.0m and 2.0m in length respectively. Subsequent drill runs will not exceed 3.0m in length. The core barrel shall be removed from the borehole as often as required to obtain the best possible core recovery. When TCR is less than 97%, or such other percentage as directed by the Engineer, for a full length drill run then the next drill run shall be reduced to a maximum of half the length of the preceding run. If core recovery is still less than 97% then drilling shall cease and the fact shall be reported to the Engineer immediately.
It might be required to ask to the Engineer for relaxing the TCR requirements in the early stages of the site work where the Contractor can demonstrate that failure to achieve the required TCR is due to his initial adjustment of drilling equipment and methods to suit the ground conditions encountered and the particular requirements of the investigation.
Following each core drill run and whenever the drill rods are removed from the borehole in rotary core drilling the depth of the borehole shall be measured to an accuracy of 10mm using a method agreed with the Engineer. The measurement shall be recorded on the daily journal and used to calculate the depth of the borehole and the length of core stub, cavings or other material present at the base of the borehole by comparison with the borehole depth determined from the length of equipment down the borehole at the end of the drill run.
If at any time blocking of the bit or grinding of the core are indicated, the core barrel shall be immediately withdrawn from the borehole regardless of the length of run which has been made. All boreholes will be fully cased through superficial and soft rock strata, to prevent water ingress and caving ground and that the casing shall be installed at 1.5m or 3m intervals (depending on run length). With the Engineer's consent other methods, such as grouting, may be used to provide support.
The ground water levels at start and end of each shift (i.e. start/end of day, start/end of lunch etc) shall be recorded at each borehole during the drilling works.
When using the semi-rigid core barrel liner shall be carefully removed in a horizontal orientation from the core barrel without vibration and in a manner which minimises disturbance of the core with gently tapping or with water pressure. The length of core retained within the core bit assembly shall be placed in its correct position in the lower end of the liner, any excess core being labelled and treated as a small disturbed sample. The liner shall be supported along its length at all times.
The liner shall then be cut so that the core fits snugly within it and its ends sealed with purpose made end-caps to prevent loss of moisture. The lengths of liner shall be labelled in the manner specified for undisturbed samples, care being taken to indicate the top of each length.
During the day, and prior to transport of the core boxes to the temporary air-conditioned site container, core boxes shall be protected from the sun by placing them in a sheded locations and laying a damp jute blanket over them.
Immediately following examination, logging or photography of the core the semi-rigid liner or polythene tubing shall be re-sealed with adhesive tape to prevent loss of moisture. The cores will be logged on site by a competent and suitably experienced Engineering Geologist or Geotechnical Engineer who shall prepare a detailed preliminary record. The detailed logging of the core shall be undertaken in the presence of the Engineer unless agreed otherwise. The photograph shall be taken of the labelled core box which shall be provided on a CD in JPG format
Fracture logging of cores shall be in accordance with the following terminology and definitions:
- Total core recovery (TCR %): percentage of core recovered (both solid and nonintact) to the total length of core run.
- Solid core recovery (SCR %): percentage of solid core recovered to the total length of core run. Solid core is defined as the length of core having at least one full diameter (but not necessarily a full circumference) and measured along the core axis between two natural fractures. By this definition core that has a single set of inclined fractures would have a solid core recovery of 100%. Where there are two or more non-parallel natural fractures, only lengths of core in which the fractures actually intersect are excluded from solid core.
- Rock quality designation (RQD %): total length of solid core pieces greater than 100mm between natural fractures expressed as a percentage of total length of core run or length of reasonably uniform characteristics where this is less than the total length of the core run.
- Fracture frequency (FF per metre): reciprocal of the average length of solid core pieces between natural fractures measured over lengths of reasonably uniform characteristics, not core runs, and expressed as fractures per metre. The term non-intact (NI) is used when the core is fragmented.
Access for the inspection of the cores by the Engineer will be provided for the duration of the Contract prior to delivery of the boxes to Botas International Ltd (BIL). All the cores will be photographed in a fresh condition prior to logging. A single colour imprint of each photograph will be submitted to the Engineer for his approval and his retention, within one week of the completion of the borehole but before the core is subsampled, destructively logged. The removal of the core liner and sub-sampling of the core shall only be undertaken in the presence of the Engineer unless otherwise agreed. On acceptance of the imprint quality by the Engineer, the core photographs shall be submitted with the Final Factual Report. The cores shall be photographed in their core boxes against a matt grey/white background and with a clearly legible notice giving the following information (Figure 14):
- Contractor's name
- Contract name and reference number
- Exploratory hole number
- Depth below ground level of the top and bottom of the core in the box and of any partition or spacer blocks
- Graduated Scale Bar
- Kodak or similar approved colour chart and monochrome step wedge.
During the drilling works a field photograph shall be taken of the labelled core box at the end of each day which shall be provided on a CD in JPG format.
Figure 14 Typical View of Label for Core Boxes.
Figure 15 Typical View of Core Box, Sub sample with Scale and Kodak colour chart.
The core and undisturbed samples shall be protected from the elements (i.e hot weather drying core/samples) while stored in an air-conditioned depot close to job site.
The undisturbed core sub samples will be placed in a purpose made rigid box and packed with nylon bobbles to reduce the damage risk during transportation to the laboratory.