GUIDELINES FOR CORE LOGGING

1 Chapter 10 GUIDELINES FORCORE LOGGINGT hese GUIDELINES incorporate procedures and methodsused by many field offices and are appropriate for"standard" engineering geology /geotechnical log forms,computerized log forms, and many of the modified logforms used by various Bureau of Reclamation(Reclamation) chapter describes the basic methods for engineeringgeology core LOGGING and provides examples andinstructions pertaining to format, descriptive data, andtechniques; procedures for working with drillers to obtainthe best data; caring for recovered core; and water testingin drill holes.

2 The chapter also provides a reference forexperienced loggers to improve their techniques and trainothers. Most of the discussions and examples shownpertain to LOGGING rock core, but many discussions applyto soil core LOGGING , standard penetration resistance logs,and drive tube sample , Use, and Importance of Quality CoreLoggingThe ability of a foundation to accommodate structureloads depends primarily on the deformability, strength,and groundwater conditions of the foundation remediation of a hazardous waste site can beformulated only by proper characterization of the and accurate portrayal of geologic design andevaluation data and analytical procedures is reported in geologic logs not only must be accurate,FIELD MANUAL250 consistently recorded, and concise, but also must providequantitative and qualitative provide fundamental data on which conclusionsregarding a site are based.

3 Additional exploration ortesting, final design criteria, treatment design, methodsof construction, and eventually the evaluation of structureperformance may depend on core logs. A log may presentimportant data for immediate interpretations or use, ormay provide data that are used over a period of log may be used to delineate existing foundationconditions, changes over time to the foundation orstructure, serve as part of contract documents, and maybe used as evidence in negotiations and/or in court toresolve contract or possible responsible party (PRP)

4 Engineering geology purposes, the basic objectives oflogging core are to provide a factual, accurate, and conciserecord of the important geological and physical character-istics of engineering significance. Characteristics whichinfluence deformability, strength, and water conditionsmust be recorded appropriately for future interpretationsand analyses. Reclamation has adopted recognizedindexes, nomenclature, standard descriptors anddescriptive criteria, and alphanumeric descriptors forphysical properties to ensure that these data are recordeduniformly, consistently, and accurately.

5 Use of alpha-numeric descriptors and indexes permits analysis of databy computer. These descriptors, descriptive criteria,examples, and supporting discussions are provided inchapters 3, 4, and should be logged or, as a minimum, reviewedby an experienced engineering geologist. The loggershould be aware of the multiple uses of the log and theneeds and interests of technically diverse users. TheCORE LOGGING251 experienced logger concentrates on the primary purposesof the individual drill hole as well as any subordinatepurposes, keeping in mind the interests of others withvaried geological backgrounds including geotechnicalengineers, contract drillers, construction personnel, andcontract lawyers.

6 An experienced logger tailors the log tomeet these needs, describing some seemingly minorfeatures or conditions which have engineeringsignificance, and excluding petrologic features or geologicconditions having only minor or academic interest. Lessexperienced loggers may have a tendency to concentrateon unnecessary garnishment, use irrelevant technicalterms, or produce an enormously detailed log whichignores the engineering geology considerations andperhaps the purpose for completing the drill descriptions of recovered cores and samples canbe prepared solely through visual or hand specimenexamination of the core with the aid of simple field microscopic or laboratory testing to define rocktype or mineralogy generally are necessary only in design methods, such as the Rock Mass RatingSystem Geomechanics Classification (RMR)

7 And Q-systemClassification (Q), are commonly used for design of under-ground structures and are coming into common use forother structures as well. If these methods are used, thenecessary data must be collected during core LOGGING . If hazardous waste site characterization is the primarypurpose of the drilling, the log should concentrate onproviding data for that type of and LOGGING are to determine the in-placecondition of the soil or rock mass. Any core condition,core loss, or damage due to the type of bit, barrel, or otherequipment used, or due to improper techniques used inFIELD MANUAL252 the drilling and handling processes should be factors may have a marked effect on the amount andcondition of the core recovered, particularly in soft,friable, weathered, intensely fractured materials or zonesof shearing.

8 Geologic logs require the adequatedescription of materials; a detailed summary of drillingequipment, methods, samplers, and significantengineering conditions; and geologic geologic logs of drill holes require adequatedescriptions of recovered surficial deposits and bedrock,a detailed summary of drilling methods and conditions,and appropriate physical characteristics and indexes toensure that adequate engineering data are available forgeologic interpretation and and Required Data for theFinal Geologic LogOrganization of the LogThe log forms are divided into five basic sections: aheading block; a left-hand column for notes.

9 A center col-umn for indexes, additional notes, water tests andgraphics; a right-hand column for classification andphysical conditions; and a comments/explanation block atthe bottom. Data required for each column are describedin the following discussion and the referenced examplelogs. Log DH-123, figure 10-1, and log B-102, figure 10-2,are the most complete and preferred examples; othervariations are presented but in some cases are heading block at the top of the form provides spacesfor supplying project identifying information, feature,CORE LOGGING253 Figure 10-1.

10 Drill hole log, DH-123, sheet 1 of MANUAL254 Figure 10-1. Drill hole log, DH-123, sheet 2 of LOGGING255 Figure 10-2. Drill hole log, B-102, for StandardPenetration Test, sheet 1 of MANUAL256 Figure 10-2. Drill hole log, B-102, for StandardPenetration Test, sheet 2 of LOGGING257 Figure 10-2. Drill hole log, B-102, for StandardPenetration Test, sheet 3 of MANUAL258hole number, location, coordinates, elevation, bearing andplunge of hole, dates started and completed, and thename(s) of the person(s) responsible for LOGGING and re-view.