Geological and Environmental Sustainability

The series of glitches that geotechnical engineers must face is increasing in complexity and scope. Often, complexity arises from the interaction between the soil and the environment. To deal with this type of problem, the classical soil mechanics formulation is progressively generalized in order to incorporate the effects of new phenomena and new variables on soil behavior. Recent advances in unsaturated soil mechanics are presented first: it is shown that they provide a consistent framework for understanding the engineering behavior of unsaturated soils, and the effects of suction and moisture changes. Building on those developments, soil behavior is further explored by considering thermal effects for two opposite cases: high temperatures, associated with the problem of storage and disposal of high-level radioactive waste; and low temperatures in problems of freezing ground. Finally, the lecture examines some issues related to chemical effects on soils and rocks, focusing in part on the subject of tunneling in sulphate-bearing rocks. In each case new environmental variables are identified, enhanced theoretical formulations are established, and new or extended constitutive laws are presented. Particular emphasis is placed on mechanical constitutive equations, as they are especially important in geotechnical engineering. The lecture includes summary accounts of a number of case histories that illustrate the relevance and implications of the developments described for geotechnical engineering practice.

A finite-element method is used to analyze the slope stability problem and to examine the effect of soil militancy on the stability of slopes. It is found that soil militancy has a significant effect on the stability of slopes, and the higher values of dilation angle lead to larger stability numbers. Therefore, the stability numbers obtained from limit analyses (lower/upper bound solutions) are not conservative for granular soils that exhibit a stretching angle smaller than a soil's friction angle. The factor of safety equations are written in the same form, knowing whether moment and (or) force equilibrium is explicitly satisfied. The normal force equation is of the same form for all methods with the exception of the conventional method. The method of handling the inter slice forces differentiates the normal force equations. A new derivation for the Morgenstern–Price method is presented and is called the 'best-fit regression' solution. It involves the independent solution of the force and moment equilibrium factors of safety for various values of λ. The best-fit regression solution gives the same factor of safety as the 'Newton–Rap son' solution.

Mining geology is an applied science which chains the principles of economic geology and mining engineering to the development of a defined mineral resource. Mining geologist and engineers work to develop an identified ore deposit to economically extract the ore. A mineral resource is a concentration or occurrence of material of intrinsic economic interest in or on the earth’s crust in such form, quality and quantity that there are reasonable prospects for eventual economic extraction. Mineral resources are further sub-divided, in order of increasing geological confidence, into inferred, indicated and measured categories. Inferred mineral resource is the part of a mineral resource for which tonnage, grade and mineral content can be estimated with a low level of confidence. It is inferred from geological evidence and assumed but not verified geological or grade continuity. It is based on information gathered through appropriate techniques from locations such as outcrops, trenches, pits, workings and drill holes which may be of limited or indefinite quality and reliability.

Civil engineering is the branch of engineering that deals with the design, construction & maintenance of roads, bridges, large buildings, airports, ports, subways, dams, mines and other large scale developments. For a civil engineering project to be successful, the engineers must understand the land upon which the project rests. Geologists study the land to determine whether it is stable enough to support the proposed project. They also study water patterns to determine if a particular site is prone to flooding. Some civil engineers use geologist to examine rocks for important metals, oil, natural gas and ground water. The value of geology in mining has long been known but its use in civil engineering has been recognized only in comparatively recent years. Geology provides a systematic knowledge of construction material, its occurrence, composition, durability and other properties. Example of such construction materials is building stones, road metal, clay, limestone & laterite. The knowledge of the geological work of natural agencies such as water, wind, ice and helps in planning and carrying out major civil engineering works.

Predictions of soil are observed and classified, and appraisals are made between predicted performance and measured performance for eight constructed facilities. Although there are many techniques for predicting internal stresses, deformations and stability for a geotechnical facility, the application of these techniques has confines. The major limitations are the difficulty of determining fully and accurately the field situation and the mechanisms which will occur, and the selection of soil parameters to use with prediction methods. The greatest need appears to be for devices and techniques to determine, in situ and continuously with depth, fundamental subsoil properties, such as stress, strength and stress-strain modulus. New concepts and methods for modeling the natural unpredictability of soil properties are presented and illustrated. The proposed technique of modeling the numerical character of soil profiles serves a dual function: It provides a format for enumerating the information are congregated during site investigation & testing, about the subsurface conditions at a site; and it provides the basis for predicting performance and for quantifying the reliability of performance predictions.  Probabilistic soil profiles are characterized, first, by best estimates of layer depths and of pertinent engineering properties; and secondly, by the coefficient of variation and the correlation scales for the contour parameters of interest. Methodology is developed for dealing with problems that can be verbalized in terms of extremes of medians of soil properties. The glitches of limit equilibrium slope stability and differential settlement prediction fall into this category.