Geotechnical Research Overview at UNH

Unless you plan to spend your career working on the space station, everything you design as a civil engineer has to eventually be connected to the earth. Research in geotechnical engineering at UNH concentrates on field and laboratory measurements of the material properties required to predict how different soils will behave under the loads applied by a structure. In some cases, the structure will be made of soil (earth dams, for example) so you will need soil properties to design the structure itself. 

As computer models of soils grow more sophisticated and complex, more and different soil properties have to be fed to them as input, including not only stresses and strains at failure, but also at working-stress levels. One problem we are working on is the development of more sophisticated field tools that are capable of measuring soil properties at a wide range of strain levels, and doing so rapidly and economically.

In-Situ Testing

Evaluation of soil properties in situ has gained more acceptance in the past few decades with recent technological developments and a better understanding of the mechanics of certain in situ tests. The main objectives of in situ testing is to allow testing of soils which are difficult or impossible to sample for laboratory testing, obtain better spatial evaluation of soil properties, test soil deposits in their natural environment and, involve a larger volume of soil than possible with conventional laboratory testing. Research at UNH has focused on several in situ tools but especially on the self-boring pressuremeter, the Marchetti flat plate dilatometer, the piezocone and the shear vane. These instruments have been modified and improved for the measurement of lateral stresses, strength and modulus values.

A new profiling tool intended for the evaluation of hydraulic conductivity in soils is currently being developed for used at shallow depth.  The probe is a modification of a tool developed in France, the Perméafor, but for deployment using portable means.  The work is undergoing as a ollaboration with the Laboratoire Central des Ponts et Chaussées in France.

Measuring While Drilling

Every day in the United States, an astonishing number of subsurface investigations and installations take place using various types of boring machines and penetration rigs. It is conceivable than more than 1 million boreholes are drilled on an annual basis in the US. Unfortunately, very little geotechnical information is retrieved from these borings since the great majority of boreholes are carried out to perform such tasks as installation of monitoring wells, water wells, deep foundations and instrumentation.

A solution to what appears as an insurmountable problem is readily available: Measuring While Drilling (MWD) or Drilling Parameter Recorders (DPR). These systems consist of computerized units and sensors which monitor a series of transducers installed on conventional drilling rigs to collect data on all aspects of drilling including advance rate, downthrust and pull-up pressures, rod torque, rotation rate, mud/water pressure and flow, depth and time. The data from the different parameters are acquired automatically. The data is displayed in real time and stored on electronic medium for further analysis. Correlations can be developed between the drilling measurements and mechanical properties of soils and rocks. The measurements can also lead to improvement to drilling equipment and techniques. These systems have been used at UNH on the Bedrock Bioremediation project in Newington, NH and in various projects in the Boston area. The work in bedrock has helped provide comparisons with various geophysical test results and with direct examination of bedrock cores. These comparisons help determine how these methods can be used most effectively, separately or in combination, to gain the most information possible about lithology, fracture patterns, strength and hydraulic conductivity of bedrock aquifers. Work using MWD is ongoing with local projects as well as part of a significant cooperation between the Laboratoire Central des Ponts et Chaussées in France and UNH. 

Smart Rocks

Collaboration between the Mechanical Engineering Department and the Geotechnical group has lead to the design of a series of smart rocks to be used in debris flow landslide research. The smart rocks are artificial metal rocks designed to measure acceleration and gyration of the rock, as well as porewater pressures as it flow within a debris mass.  In the summer of 2011, the rocks were deployed at the United States Geological Survey Debris-Flow Flume facility located at the US Forest Service HJ Andrew Experimental Facility in the Willamette National Forest in Oregon.  The flume, 95 m long and 2 m wide, provided a test bed for evaluating the first version of the smart rocks.  Work is continuing to further miniaturized the rocks and evaluate the acquired data in hopes of providing valuable insight into landslide mechanics, prevention and security measures. This work is coupled with laboratory triaxial and ring shear testing of the soils involved in the sliding mass.

Harvesting Wind Energy From Bridges

This project, funded by the U.S. Environmental Protection Agency, investigates the use of wind patterns from traffic and natural flow through bridge underpasses to harvest energy for powering lighting, signalization, emergency warnings and structural health monitoring.  Although not a geotechnical topic, the use of renewable energy is relevant for numerous geotechnical applications.