Sonic Drilling and Sampling methods

Sonicbore have several sampling techniques at their disposal and are currently developing new ones. Samplers to obtain cores of up to 150mm diameter are being tested.

Sonic Core Sample

The GP100 system drills a 100mm diameter hole and takes a 76mm sample which is recovered in a clear upvc liner 1500mm long. The recovered sample is immediately sealed with endcaps to retain any volatiles. Versatility is one of sonicbore’s major benefits, there is even a suite of window sampling type tubes if the client prefers in which you will have similar un-disturbed samples. When drilling superficial deposits, it is common to come across cobbles and boulders. If sonic methods reach refusal the tools are withdrawn and a fragmented tungsten cutting shoe is fitted and the tools are re-inserted into the borehole. The drillhead is set to rotary mode and the obstruction is cored (without flush). Once the obstruction is penetrated, the drilling can be switched back to sonic mode.

The N70 system the same as the GP100 system but drills a 70mm diameter hole and takes a 57mm core.

The Aqualock system is the jewel in the crown and drills a 70mm diameter hole and takes a 48mm core. This newly patented system takes 2mtr long cores. The beauty of the Aqualock is that it can sample any discreet section of a borehole that is of interest for example a change in strata or a known layer of contamination on top of clay. We call this spot coring.

When spot coring, the tool is driven to the desired sampling start depth in the non-sampling mode. A mechanism is released then at the back of the Aqualock which in turn frees a plunger that up to this point has been held at the leading face of the tool. Sonic penetration is restarted and a 2mtr sample is now taken. The locking mechanism at the back of the Aqualock is then closed and the resultant suction keeps the sample in the sampling tube. The tool is withdrawn and the sample is hydraulically extruded into a sample tray using a high pressure water pump built into the rig. This exercise can be repeated until the desired section of the borehole has been sampled. On completion of a well, a monitoring point can be installed or if no monitoring is needed then pre-formed sticks of bentonite can be placed over the full length of the well before removal of the drill string. The drill string is then removed and the bentonite swells to fill the hole ensuring that all paths for contamination are blocked. This system saves time and money as it concentrates on the areas of interest in a borehole. Clients are amazed at the quality of sample the Aqualock can take. On one particular site the samples clearly define 1mm layers of solidified chemical in sands and silts at depths in excess of 20mtr. From setting up on the well to having the sample to log takes less than an hour on this particular site.

Lost point drilling

Occasionally there is a requirement for installations such as piezometers, placement of seismic charges or sparging wells but no need to take samples.

This is where sonicbore uses the lost point system. Either 100mm or 75mm wells are drilled. The drill string is fitted with a disposable tip (lost point) and then driven with sonic vibrations to the desired depth. The rods are lifted off the bottom of the well leaving the disposable tip and the installation is carried out through the rods i.e. in a fully cased hole. Using the lost point method, wells have been drilled to 30mtr depth in sands and silts in as little as 4 minutes actual drilling time. Imagine, a piezometer to 20mtr installed with no mess and site cleared in less than half an hour!!!