Lankelma completed two commercial projects backfilling CPT holes using a CPT operated grouting module named the Soil Injection Probe.  The projects showed limitations in the system, all of which can be overcome with further testing and modification. The second project performed went some way towards this.

The current trend where contaminated ground, poorly engineered or natural ground with unsuitable engineering properties is to treat/stabilise in situ.

It is proposed to modify the system still further to enable the system to be used to treat contaminated soils in situ by bio-remediation techniques.

 
Government Policy

Under Government policy, all developments are to consider utilising brown-field sites over and above green-field sites.  Therefore, particularly where contaminated soil is present two options are currently available; ex-situ treatment or in-situ treatment.

 
Contaminated Ground

The former requires removal of the contaminated soil, treatment off-site and then either disposal to licensed tip (with excavation being replaced with inert soil) or returned to site.

In-situ treatment is preferable in all cases as contaminated soil in situ is generally at relative equilibrium.  Where relatively stable, disturbance by excavation enables remobilisation of contaminants, which is exacerbated by groundwater presence and flow.

 
Proposed Method

The existing system is small diameter (36mm), however, should further works prove necessary, a 55mm diameter system could be made using existing equipment conventional ad adaptable to CPT equipment.  This   theoretically would enable greater and more rapid injection of bio-agent or stabilising agent into the ground.
 
 
Current Methods
 
Current methods of in-situ treatments include probing and flushing, injection of bio-agent and bio venting (installing well pipes for circulation of oxygen etc). This is performed by shallow surface probing (DP or rod injection) or deeper probing by piling rigs which inject bio-agent as with concrete in helical-displacement-pile (HDPs).  It is worth noting that HDP’s are not dynamic in there operation like other probe/injection methods and as a method technique it is the only piling technique endorsed by the EA in on sites underlain by sensitive aquifers. 
 
   
Outline of Advantages of Proposed System
  
It is proposed that Lankelma’s SIP could be used to greater effect over any other method, with the following advantages:

• Static hydraulic installation of probe – minimise soil disturbance and potential draw-down of contaminants from contaminated layer to underlying ‘clean soil’

• Rapid progress and high productivity;

• Where cone penetrometer is used in front of the SIP system, accurate profiling of the contaminated soil can be performed real-time and so treatment of the full depth of contaminated unit can be performed.  Existing non-instrumented systems take an arbitrary depth previously determined by ground investigation and subsequent model.

• In general, contaminated soil units to be treated are made ground/fill.  This is generally softer/less dense than natural strata and so ideal for the penetration capabilities of the CPT system.