Environmental geotechnology

Background to the study

The pollution of ground (geological environment) has long been deteriorating while air and water pollution have been outstanding environmental issues for the last half century. Such pollution has been generated because the earth has been used as a gigantic waste disposal site for pollutants such as improper landfill of waste and the penetration of industrial and domestic wastewater underground without due consideration. Recently, groundwater pollution has become a social issue, but it is only an apparent phenomenon of geological environmental pollution, and clarifying the overall picture of ground pollution and restoring the environment will be major environmental issues in the 21st century.

On the other hand, parts of the globe where populations have continuously expanded have been permanently changed in environment. Such a concentration of population changes the subsurface thermal environment, or increases the risks of ground disasters. In particular, residential land has been developed on delicate swampland due to a lack of suitable housing space on the plains of the prefecture situated in the metropolitan region. This causes increased risks in the event of a disaster in urban areas, while it has been conjectured that a substantial earthquake may occur in the near future.

There are also concerns that environmental issues which damage good living environments, such as noise and vibration problems, have simultaneously been increasing on lines with increased overcrowding.  

Under such circumstances, comprehensive measures are in the following study areas to encourage a safe and proper land use and conserve the optimal geologic environment within the prefecture.

1. Studies on geotechnical information management
2. Studies on risk evaluation against natural and artificial disasters
3. Studies on subsurface thermal environment
4. Studies on countermeasures against noises and vibrations 

Current research topics

Studies on geotechnical information management

Information on the underground, such as level of aquifers and ground water tables, is required to clarify the spread of groundwater contamination. Geological/geotechnical information is being accumulated on subterranean features across the entire prefecture and the geological characteristics analyzed by collecting and studying the data of existing drilling logs and surveying the subterranean structure. A database has been completed with statistics of about 11,000 geological drilling logs that are retained by each department concerned in the prefectural office for 'collecting analyzing drilling data', and analysis of the distribution of geological features of the outer layer and depth distribution of alluvium has begun. Such data is used for environmental studies such as on geological characteristics and by the administrative departments concerned.

      

Studies on risk evaluation against natural and artificial disasters

The mechanisms of geological damages caused by soil and groundwater contamination, earthquakes are being clarified, and promotion of mid- to long-term measures to solve and prevent each pollution problem and reduce damages is being supported. Under such circumstances, this group carry out the following research topics and investigations on soil and groundwater contamination. Preservation of soil environment is very important from the view point of sustainability of a high quality water source.

• On-site analysis of hazardous metals in soil and groundwater ( Fluorescence X-ray analysis, Electrochemical analysis）

• Leaching property of hazardous metals from terrestrial soils and marine sediments  

• Development of simple and rapid method to identify of contaminated soils   

• Studies on soil contamination caused by natural process

• Investigation of soil and groundwater contamination based on soil contamination countermeasures low and water pollution control low

    

On the other hand, the geological analysis, various physical surveys (*Note) and development of new survey techniques are also being carried out by this group. These analysis and surveys are very useful for identifying sources and areas of contamination, and also useful for evaluating the degree of local earthquake risks.

(*Note) Techniques to enable the situation of underground to become visually apparent, by observing electromagnetic wave or elastic wave that are propagated through the ground 

      

Studies on subsurface thermal environment

Subsurface thermal environments are investigated from two points of view. First, subsurface thermal environments have been changed by human activities. It may lead up to risks of ground disasters. The subsurface warming is investigated through subsurface temperature measurements. Second, borehole heat exchanger system is effective as economical and environmentally friendly energy technology. To construct a database for application of borehole heat exchanger system in Saitama, geological information, subsurface temperature distribution, and hydrogeological properties are compiled.