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The writing's on the wall A new field-based handheld computer could improve the accuracy and consistency of borehole logging.

One of the key aspects of site investigation work is the ability to produce accurate and comprehensive exploration borehole descriptions in the shortest possible time.

Borehole logs often contain errors that are sometimes missed, even with extensive checking and rechecking. Descriptions may not be consistent and are dependent on who has logged the core. All in all, it is a time- consuming and often inefficient way of recording site investigation data.

However, handwritten field logs could soon be a thing of the past with the development of a new handheld computer logging tool. The Psion Geologist, an 'on-site one-time data capture system', was developed by Tree Technology and the Bachy Soletanche Group, primarily for the Hong Kong market.

Recording the logging electronically on site removes many of the potential logging errors and saves time by downloading directly to software that produces borehole logs.

The system, which uses a Psion WorkAbout handheld computer, was developed for rotary core and vibrocore logging.

The software logs to the Hong Kong Geoguide 3 standard - based on BS5930 - and is designed in such a way as to guide the engineer through the logging process in a logical order using a series of menu driven screens.

The engineer first has to record the run details, core length, zones of no recovery and the fracture index before describing the soil and rock, which should reduce mistakes in locating material boundaries.

Where the system really scores is that it will not allow descriptions such as 'firm sand' or 'loose clay' and more sophisticated checks (there are over 3000 in all) include cross-referencing of the fracture index with the RQD to ensure realistic joint spacing descriptions are entered.

To reduce the amount of moving of coreboxes, the system allows sections of boreholes to be input, with up to nine boreholes being logged simultaneously.

Once logging is finished, the data can either be transferred to the office using a modem or downloaded onto a laptop or PC at the touch of a button. Data processing is also carried out at this stage, with data formatted to Hong Kong Geoguide 3. The system is designed for importing into gINT, the borehole record package used by many Hong Kong site investigation contractors, and the option to convert the data ready for this step can be carried out. It is at this stage that the engineer can edit the data.

Engineers can be brought up to speed with minimal training - just three hours, says Tree Technology's Mark Whitmarsh, even for those unfamiliar with computers and those reluctant to change from traditional logging methods.

Despite some early teething problems, field trials and operational use have shown that errors in logging are reduced and logging time is said to be up to 20% faster, by removing the need for rewriting of the logs.

The WorkAbout is lightweight and waterproof and is robust enough to be dropped onto concrete from a height of 1m. It will operate for 'weeks' on two small batteries and can store 300 to 15,000 borehole logs depending on whether computer disks are used.

The Psion Geologist was first used by Bachy Soletanche in June 1998 on the urban term contract for Hong Kong's Geotechnical Engineering Office. In March this year, the product was released commercially in Hong Kong, where Lam Geotechnics was the first firm to take up the system. Bachy Soletanche has also used the package on construction of one of the stations on the Mass Transit Railway project for bored piling and diaphragm walling.

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