This was written some time ago to explain to the curious but non-technical what it is we do…
We make instruments for measuring the strength of ground considered as an engineering material on which or in which to build structures. We make the instruments for sale and we also own several sets of our own equipment which we hire out, with one or two of us to operate it, to make measurements on particular projects. Typical of these are the Second Severn Crossing, the stations on the new Jubilee Line Extension, the CrossRail Project, the Bangkok Wastewater Outfall Tunnel, Singapore Changi Third Runway and the Singapore and Bangkok Mass Rapid Transit tunnels. All of the motorway widening projects of recent years have involved our instruments sometimes driven by us and sometimes by others.
We didn’t invent our principal instrument, the Cambridge Self-boring Pressuremeter. It was developed in the Cambridge University Engineering Department in the early 1970s by the late Professor Peter Wroth and Dr John Hughes. We saw working prototypes which we improved fairly extensively and for which we designed all the rest of the equipment for drilling, for controlling the tests, for reading the results, for analysing the data and including writing most of the software The instruments are basically varieties of pressuremeter, tubular instruments on the outside of which is a rubber or plastic sleeve which can be expanded by internal gas or oil pressure. They go down boreholes which they either make themselves or are made for them by a site investigation contractor, the choice depends on the ground. Once at the interesting depth the expansion is started and measurements made inside the downhole tool of the pressure and the corresponding increase in size of the borehole. The resulting graph of pressure against size increase gives the ground failure strength and how it deflects under loads. The derivation is mathematically rigorous. We can also measure the pressure in the water between the soil granules which, in clays and some sands, is very important and useful information.
With the coming of complex integrated circuits we now put computers down the borehole and this has greatly improved the performance of the instruments. They are routinely hit with a hammer and they still measure to better than a thousandth of a millimetre, one micron. We have sets of our equipment in most parts of the world including China and Japan, Canada, the USA, Brazil, Australia, South Africa, Europe and so on. The proportion of exports varies widely between some 20% and 70% of turnover. We sell these instruments under the name Cambridge Insitu. The Insitu bit comes about because the instruments are operating on the ground in its original position, down the bottom of the borehole. The parent company is called Deep Body Thermometers Limited for that is what it originally made. These measure the core or deep body temperature of humans and other mammals without putting anything in any of the available holes. It started in 1971 partly as a spin off from Grant Instruments. We got involved with soil mechanics less than two years later and it has gradually taken the company over to the point where we are thinking of changing its name. However Philip Hawkins says reasonably that the existing name is not forgotten by any supplier even if we have not bought anything for years.