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Priority Geotechnical Ltd. have undertaken rotary drilling for our Clients throughout the country encountering a wide variety of rock types from soft to strong sedimentary rock and very strong igneous rock.

PGL have also undertaken rotary drilling with core recovery through stiff to very stiff boulder CLAY (slightly sandy slightly gravely CLAY, with cobbles and boulders) with a very good percentage recovery allowing for a detailed profiling of the soil where cable percussive boring was unable to progress due to large obstructions.

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Rotary drilling

Priority Geotechnical Ltd. have 3 number track mounted rotary rigs: 2 number Delta Base S20 and 1 number Soil Mech PSM 8G.

These rigs are capable of drilling both rotary percussive, open-hole (using Symmetrix 115 or 131 systems) and core recovery with double or triple tube systems. Priority Geotechnical can drill boreholes, using open- hole drilling up to 250mm in diameter to depths of 40m and rotary drilling with core recovery from between 48mm to 120mm diameter core to depths exceeding 100m. Rotary drilling uses air-mist, polymer foam or water flush to aid coring. We can provide rotary drilling with core orientation for the detailed logging of fractures where required. Standard Penetration Test, N values may be undertaken through the overburden materials to characterise the overburden strength and relative density. In- situ, down-hole geophysics, optical and acoustic televiewers can be undertaken upon request to further characterise fracture orientation and spacing.

Our track mounted rigs can traverse most terrain and access soft ground sites with or without the aid of “bog mats”. The compact size of the rigs and compressors allow for access to small sites to undertake rotary drilling, with the exception of restricted head room sites. Our rotary drillings are also suitable for mounting on floating plant and jack-up barges for over-water and marine drilling. These capabilities allow Priority Geotechnical Ltd. to provide for our Clients needs whatever their rotary requirements.

Upon completion of rotary drilling experienced Engineering Geologists log the recovered core, measuring total core recovery, TCR, solid core recovery, SCR, Fracture spacing, Fracture Index, FI and Rock Quality Designation, RQD. These parameters along with the rock type enable the engineering characteristics of the rock to be determined for design purposes. Priority Geotechnical can undertake rock testing, Point Load Index and Unconfined Compressive Strength Test, to determine the rock strength further assessing the rock mass. Detailed geotechnical logs are prepared using AGS compatible software.

Priority Geotechnical Ltd. can provide interpretive reporting on the rock mass characteristics, where required allowing for determination of suitable methods of excavation, stable angle for cutting and the suitability of re-use as an engineering material.

All fieldworks are carried out in accordance with the relevant British Standards: BS 5930.

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