The focus of a geotechnical exploration in sinkhole-prone areas is to locate potential problematic subsurface conditions and define their extent.
Since the cavities in the rock and the voids in the overburden are buried deep underground, and since subsurface conditions vary throughout the state, various exploration and data-gathering techniques are used:
Existing Data: We first study the geology and hydrogeology through existing maps and aerial photographs, publications, contacting local agencies and landowners, and reviewing Ardaman's extensive year database of prior investigations.
Soil Borings: Rotary wash borings with Standard Penetration Tests provide specific and accurate information on soil and rock stratigraphy as well as soil strength and consistency, and location of voids and loose raveling zones within the overburden.
Cone Penetrometer Soundings: These provide similar information as the soil borings, but they can be conducted faster and more economically, allowing more data to be acquired within a stated schedule and budget. The electric piezocone can be effective for detecting slight downward hydraulic gradients often present near breaches in the confining layer.
Groundwater Monitoring Devices: The level of the upper groundwater table will frequently depress above and near confining layer breaches. This level can be monitored and contoured through a series of selectively placed piezometers.
Geophysical Methods: Geophysical techniques such as ground penetrating radar, electro-magnetic conductivity, and seismic surveys can detect anomalies in the overburden profile. These methods are somewhat interpretive, but are useful for providing a significant amount of data, relatively quickly, that can be used to design the final drilling and testing program.
One or more of these exploration methods are used to evaluate the sinkhole potential of a site. The most important tool, however, is the knowledge and experience of the engineers conducting the investigation. They will know the most efficient and effective technique to apply in any given situation. At Ardaman, our engineers do not use technology for its own sake. Rather, we endeavor to apply the proper level of study that will obtain the appropriate information within the schedule and budget requirements.
