VWPs & Casagrande Standpipes

Various direct-push installation methods and sealing systems are used, depending on circumstances and conditions in the field.  

Methods can be (and often are) tailored to suit a client’s preferences or instruments. We can install client supplied VWPs or supply VWPs to clients specifications. Our preferred VWP supplier is HMA Geotechnical. 

We have developed a few methods to install vibrating wire piezometers:

• The simplest, and we believe the most “elegant”, method is shown in the adjacent figure.  A standard 19mm diameter VWP is sealed into our own-designed VWP Adapter, and dummied/direct-pushed to installation depth.  Sealing is achieved via the stainless-steel adapter itself, having a section above the VWP which is a larger diameter, and is thus forced into intimate contact with the soil.   The adaptor itslef has a sand filter around the VWP sensor and is sealed with  beontonite and wax within the stainless steel casing. 
• The most complex method, now seldom requested by clients, involves installation by insertion through our 55mm OD CPT casing tubes, followed by placement of a small sand filter then bentonite pellet sealing.
• Other methods are possible and available – if required.
  

As we are able to test the VWPs after placement within the fabricated adaptor, but prior to placement in the ground, we have a very high success rate in installation of VWPs by this direct push method compared with traditional drilled installation methods.