Judgment and Innovation: The Heritage and Future of the Geotechnical Engineering Profession

This paper addresses linkages between geoenvironmental practice and geotechnical engineering. The early development of the field that we now call "geoenvironmental engineering" or "environmental geotechnics" is traced. Attention is focused on examples of areas of geoenvironmental practice that are closely linked with the geotechnical field of practice. Many of the experiences and lessons learned from geoenvironmental engineering are applicable to geotechnical practice, particularly the knowledge gained from site investigation, clay liners, geosynthetics, and landfill stability problems.

Measurements are essential to geotechnical practice. This paper examines the current state of geotechnical measurements in terms of the advances that have been made and the retreats that have accompanied these advances. Laboratory measurements are used to obtain mechanical and physical properties of geologic materials for analysis and design. Modern electronics makes possible a wide variety of laboratory tests to measure strength, stress-strain behavior and permeability. Automated testing systems offer many advantages, but they also produce problems. Capabilities of automated testing systems are presented and discussed along with advantages and problems. Field measurements of performance have been central to advancements in geotechnical practice. Experience gained from one of the largest geotechnical instrumentation programs ever undertaken is presented and discussed. The paper concludes with some observations about the current state of geotechnical measurement practice.

Breakthroughs in geotechnics in the next century may not be as revolutionary as those in the 1920s and 1930s, but geotechnical engineers will face challenging jobs, particularly in combining soils with other materials and by reducing the adverse impact of construction works on our social fabric.

Progressive internal erosion by piping still presents a major failure threat to dams built with and/or over cohesionless soils. Many engineers do not understand the mechanics of piping and design using an empirical method more than 60 years old. We now know enough to improve this situation. A review of 115 horizontal piping tests indicates the predominant importance of a sand's coefficient of uniformity in determining the hydraulic gradient needed to develop piping, with layer depth, pipe length, density, anisotropy, layering and inclination also having important effects. This paper adds to our physical knowledge about piping, connects piping with liquefaction and presents a new test-based design method for determining the factor of safety and reliability vs. piping at any point in a trial piping path in cohesionless soils. When using filters for safety vs. piping, the new method provides redundancy. It uses the simplifying concept that very low effective stresses and the vertical seepage gradients at the advancing end of the pipe determine its advance, and that the pre-pipe gradients at any point in the pipepath have an important effect on the degree of safety at that point. Section 6 presents a design method for the safety factor vs. piping, with an example. Sections 2 through 5 give the theoretical and practical details leading to the new method. Section 7 discusses some of the possible criticisms of the method.