Bedrock is the hard, solid rock most often found beneath the unconsolidated surface materials, such as sand or till, but also as outcrops above the ground surface. The depth to the rock head can vary from zero to several hundred meters and the topography, as well as the quality, of the bedrock can differ significantly.
An understanding of the bedrock is important for many aspects of human activities on Earth. Knowledge of the depth to the bedrock and its properties are essential for:
Today, most bedrock investigation is done by digging or drilling but with the increased use of 3D design tools (on infrastructure and resource mapping projects, for example) the demand for more data coverage is increasing. Attempting to resolve this need with traditional intrusive methods will be extremely expensive and sometimes, with an increasingly ‘crowded’ subsurface, digging and drilling can be most undesirable and risky. Instead, different geophysical tools can be used to assist in the creation of a more comprehensive picture of the bedrock conditions.
Guideline Geo´s wide range of geophysical investigation techniques can solve most of the common questions that instigate some form of bedrock mapping. They will give a non-destructive and cost-efficient way of gaining a better understanding of the ground conditions, providing better data coverage than is normally achieved with traditional, discrete, point-by-point geotechnical investigations, such as drilling or digging.
In Table 1 the most common bedrock applications and a range of possible geophysical techniques for their investigation are listed. Guideline Geo provides both GPR, resistivity, seismics and TEM solutions for bedrock investigations. Note that all solutions provide output as position (XY) and depth (Z) against some other parameter such as depth to bedrock, which can be transferred easily to GIS or CAD applications.
GPR is suitable for:
Guideline Geo provides a number of different GPR solutions for bedrock applications, most common being the MALÅ GX and MALÅ ProEx ranges; visit the product pages below for more information. The processing and interpretation of the collected data can be done in different software packages, depending on application. More information can be found below.Suitable software is for example Reflexw or GPR-Slice.
Resistivity is suitable for:
Seismic survey is suitable for:
Guideline Geo’s ABEM Terraloc products are incredibly versatile and can be configured to undertake practically any type of seismic data acquisition; the only choice is the scale of system in terms of how many measurement channels are required. A very wide range of 3rd party processing packages available from Guideline Geo ensures that the perfect solution can be found for your particular application.
Whilst there are many factors involved in deciding upon the correct solution for a given project, these are some of the key considerations:
It is often beneficial to combine different geophysical methods to get the best resulting picture of the bedrock conditions due to the overburden conditions, the physical distribution of the bedrock or level of information required. For instance: