Tunnel Engineering Handbook
carried out by engineering geologists, geological engineers, geotechnical engineers, and geologists and civil engineers with education and experience in geotechnical investigations. Geologic conditions at a site are a major influence on the environmental impact and impact mitigation design, and therefore a primary portion of geotechnical investigations is to observe and report potential conditions relating to environmental impact. Factors influencing the selection of methods of investigation
... lude: a. Nature of subsurface materials and groundwater conditions. b. Size of structure to be built or investigated. c. Scope of the investigation, e.g., feasibility study, formulation of plans and specifications. d. Purpose of the investigation, e.g., evaluate stability of existing structure, design a new structure. e. Complexity of site and structure. f. Topographic constraints. g. Difficulty of application. h. Degree to which method disturbs the samples or surrounding grounds. i. Budget constraints. j. Time constraints. k. Environment requirements/consequences. l. Political constraints. 1-5. Scope of Manual Increasingly, geotechnical investigations are conducted to evaluate the condition of existing projects as part of Operations and Maintenance. This type of investigation places special constraints on the methods which may be used. These constraints should be kept in mind by the designer. a. General. Geotechnical investigations for roads and airfields are not discussed. Geotechnical investigations at construction sites may involve exposure to hazardous and toxic waste materials. In cases where such materials are recognized, geotechnical investigators should contact the Mandatory Center for Expertise for assistance. It is of note that many of the techniques and procedures described in this manual are applicable to hazardous, toxic, and radioactive waste (HTRW) work. Geotechnical aspects of HTRW site assessment are discussed in Construction Site Environmental Survey and Clearance Procedures Manual (Draft), EM 1110-1-4000, Walker (1988), and Borrelli (1988). b. Types of detailed discussions. Chapter 2 provides guidance on geotechnical investigations appropriate to various stages of project development. Chapter 3 provides for implementation of initial, regionally oriented geotechnical investigations. Chapter 4 provides guidance for field procedures for surface investigations. Chapter 5 provides guidance on subsurface investigation procedures. Chapter 6 describes procedures for large-scale, prototype investigations, and Chapter 7 describes laboratory EM 1110-1-1804 1 Jan 01 1-3 procedures for characterizing geotechnical properties of materials. Appendices and subject matter covered are: Appendix B, details for geologic mapping of construction areas; Appendix C, geologic mapping of tunnels and shafts; Appendix D, examples of drilling logs; Appendix F, soil sampling; and Appendices G and H, penetration resistance testing. Appendix F includes the modified version of the engineering manual on soil sampling. Information on soil sampling is also contained in Appendix C of EM 200-1-3. The text references specific sections of the soil sampling EM where appropriate. Guidance is in general terms where methodologies are prescribed by industry standards and described in accessible references. Where descriptions are otherwise unavailable, they are provided herein. The manual intends to provide general guidance to geotechnical investigation; because of the variability that exists among Corps of Engineers (COE) Districts or Divisions, it is advisable that each district and division prepare separate field investigations manuals. The manual should highlight procedures and formats of presentation that are preferred for geotechnical investigations within that organization. These manuals should be consistent with applicable EM.