Geotechnical Challenges in Highway Engineering in Twenty First Century: Lessons from the Past Experiences and New Technologies

The Transportation Authorities and Highway Engineers around the world are facing different types of challenges today than their counterparts in the nineteenth and twentieth centuries. These challenges include developing new highways and bridges as well as retrofitting of existing roads and bridges deteriorated due to aging or increased vehicle loading. Frequencies of deterioration of existing roads and imminent bridge failures forced many Highway Authorities to evaluate the existing roads and bridges and prioritize their retrofitting to comply with current specifications and future conditions. The new challenges of today include, but not limited to: a) Construction over poor foundation materials such as organic soils, old landfills, expansive and collapsing soils and non-availability of alternative routes; b) Right-of-way restrictions including construction in urban areas and proximity of existing structures; c) Dealing with environmental concerns that were not considered critical in the past and complying with stricter environmental and safety regulations.; d) Utilization of certain native on-site materials (considered problematic such as shale) in back fills and embankments; e) Higher vehicle loading as well as increase in size and number of vehicles; f) Expectations of the road users for better driving conditions, safety improvements and riding quality. These challenges can be overcome by applying innovative ideas and using modern technology during planning, design and construction stages of highway development. This paper identifies some of the new challenges of today based on past history and presents various tools to meet these challenges. With better and faster methods of analysis, use of new construction materials (such as low density fill materials, geo-synthetics, geo-foam, tensors), utilization of new procedures (such as soil stabilization, reinforced earth, soil nailing ) and implementation of effective planning, execution and quality control, these challenges can be overcome in an efficient and cost effective manner. This paper also identifies various current geotechnical practices, which may be considered inadequate for modern-day highway design and construction, but have not been updated for decades. In conclusion, recommendations for revisions to inadequate geotechnical practices are presented in this paper in order to provide safe and sound design and construction guidelines from geotechnical viewpoint

Stabilization of a Failed Highway Slope: A Multi-Phased Approach

A county road department in Southeastern Michigan was faced with the problem of stabilizing a slope along the Clinton River supporting a heavily trafficked roadway. The roadway and supporting slope had performed satisfactorily for over 50 years. However, a reinforced concrete seawall that had partially supported the slope deteriorated over time, contributing to progressive failure of the slope and resulting damage to the roadway. The site is situated within the glacial lake plain district of Southeastern Michigan. The site geology consists of approximately 7 feet of over-consolidated clays underlain by approximately 17 feet of normally consolidated glacial-lacustrine clays. Below the normally consolidated clay, highly over-consolidated sandy clay till and dense fine to medium sands are present. The sands contain a confined aquifer with a hydrostatic head on the order of 20 feet. The 14-foot high, 35 degree slope has experienced progressive, creep type movement since approximately the year 2000 resulting in settlement and cracking of the roadway shoulder and pavement. Maintenance procedures to maintain serviceability of the roadway created increased surcharge loads that appear to have precipitated further creep movement. Our analyses indicated the unreinforced slope possessed a factor of safety of approximately one or less with respect to global and direct sliding failure mechanisms under both drained and undrained conditions. A number of alternatives were considered to obtain the desired factory of safety values. Upon analysis, these alternatives were not considered satisfactory due to failure to meet the project objectives, typically cost and/or failure to obtain the desired factor of safety against slope failure. A multi-phased approach was selected that was aimed at both reducing the destabilization forces as well as increasing the resisting forces by replacing the upper portion of the slope with geogrid-reinforced lightweight, angular blast furnace slag, and intercepting the slope failure surface with passive piles extending into the highly over-consolidated sandy clay till and/or dense sands. This approach allowed the project objective to be met with the work being accomplished on schedule and within budget. A cost savings of approximately $400,000 was realized with respect to other stabilization alternatives

Shales as Embankment Materials

Abstract not availabl

SHALES AS EMBANKMENT MATERIALS

Abstract not availabl