Regulatory Guide 1.132
| ML032790499 | |
| Person / Time | |
|---|---|
| Issue date: | 10/31/2003 |
| From: | Office of Nuclear Regulatory Research |
| To: | |
| References | |
| RG-1.132, Rev 2 | |
| Download: ML032790499 (15) | |
1As determined by the final locations of safety-related structures and facilities.
2Includes shafts or other accessible excavations that meet depth requirements.
APPENDIX D
SPACING AND DEPTH OF SUBSURFACE EXPLORATIONS FOR SAFETY-RELATED1 FOUNDATIONS
STRUCTURE
SPACING OF BORINGS2 OR SOUNDINGS
MINIMUM DEPTH OF PENETRATION
General For favorable, uniform geologic conditions, where The depth of borings should be determined on the basis of the type continuity of subsurface strata is found, the of structure and geologic conditions. All borings should be extended recommended spacing is as indicated for the type to a depth sufficient to define the site geology and to sample all of structure. At least one boring should be at the materials that may swell during excavation, may consolidate subse- location of every safety-related structure. Where quent to construction, may be unstable under earthquake loading, or variable conditions are found, spacing should be whose physical properties would affect foundation behavior or smaller, as needed, to obtain a clear picture of stability. Where soils are very thick, the maximum required depth soil or rock properties and their variability. Where for engineering purposes, denoted dmax, may be taken as the depth at cavities or other discontinuities of engineering which the change in the vertical stress during or after construction significance may occur, the normal exploratory for the combined foundation loading is less than 10% of the work should be supplemented by borings or effective in situ overburden stress. It may be necessary to include soundings at a spacing small enough to detect in the investigation program several borings to establish the soil such features.
model for soil-structure interaction studies. These borings may be required to penetrate depths greater than those required for general engineering purposes. Borings should be deep enough to define and evaluate the potential for deep stability problems at the site.
Generally, all borings should extend at least 10 m (33 ft) below the lowest part of the foundation. If competent rock is encountered at lesser depths than those given, borings should penetrate to the greatest depth where discontinuities or zones of weakness or alteration can affect foundations and should penetrate at least 6 m
(20 ft) into sound rock. For weathered shale or soft rock, depths should be as for soils.
3Also supplementary borings or soundings that are design-dependent or necessary to define anomalies, critical conditions, etc.
4Includes temporary cuts that would affect ultimate site safety.
Appendix D, Continued STRUCTURE SPACING OF BORINGS OR SOUNDINGS
MINIMUM DEPTH OF PENETRATION
Buildings, Principal borings: at least one boring beneath At least one-fourth of the principal borings and a minimum of retaining every safety-related structure. For larger, one boring per structure to penetrate into sound rock or to a walls, heavier structures, such as the containment depth equal to dmax. Others to a depth below foundation concrete and auxiliary buildings, at least one boring per elevation equal to the width of structure or to a depth equal to dams
900 m2 (10,000 ft2) (approximately 30 m the width of the structure or to a depth equal to the foundation
(100 ft) spacing). In addition, a number of depth below the original ground surface, whichever is greater.3 borings along the periphery, at corners, and other selected location
s. One boring per
30 m (100 ft) for essentially linear structures.
Earth dams, Principal borings: one per 30 m (100 ft) along Principal borings: one per 60 m (200 ft) to dmax. Others dikes, axis of structure and at critical locations should penetrate all strata whose properties would affect the levees, perpendicular to the axis to establish geological performance of the foundation. For water-impounding embank- sections with groundwater conditions for structures, to sufficient depth to define all aquifers and zones ments analysis.2 of underseepage that could affect the performance of structures.2 Deep cuts,4 Principal borings: one per 60 m (200 ft) along Principal borings: One per 60 m (200 ft) to penetrate into canals the alignment and at critical locations sound rock or to dmax. Others to a depth below the bottom perpendicular to the alignment to establish elevation of excavation equal to the depth of cut or to below geologic sections with groundwater conditions the lowest potential failure zone of the slope.2 Borings should for analysis.2 penetrate pervious strata below which groundwater may influence stability.2
Appendix D, Continued STRUCTURE
SPACING OF BORINGS OR SOUNDINGS
MINIMUM DEPTH OF PENETRATION
Pipelines Principal borings: This may vary depending Principal borings: For buried pipelines, one of every three to on how well site conditions are understood penetrate sound rock or to dmax. Others to 5 times the pipe from other plant site borings. For variable diameters below the elevation. For pipelines above ground, conditions, one per 30 m (100 ft) for buried depths as for foundation structures.2 pipelines; at least one boring for each footing for pipelines above ground.
Tunnels Principal borings: one per 30 m (100 ft),2 may Principal borings: one per 60 m (200 ft) to penetrate into vary for rock tunnels, depending on rock type sound rock or to dmax. Others to 5 times the tunnel diameter and characteristics and planned exploratory below the invert elevation.2,3 shafts or adits.
Reservoirs, Principal borings: In addition to borings at the Principal borings: At least one-fourth to penetrate that portion impound- locations of dams or dikes, a number of of the saturation zone that may influence seepage conditions ments borings should be used to investigate geologic or stability. Others to a depth of 7.5 m (25 ft) below reservoir conditions of the reservoir basin. The number bottom elevation.2 and spacing of borings should vary, with the largest concentration near control structures and the coverage decreasing with distance upstream.
Sounding = An exploratory penetration below the ground surface used to measure or observe an in situ property of subsurface materials, usually without recovery of samples or cuttings.
Principal boring = A borehole used as a primary source of subsurface information. It is used to explore and sample all soil or rock strata penetrated to define the site geology and the properties of subsurface materials. Not included are borings from which no samples are taken, borings used to investigate specific or limited intervals, or borings so close to others that information obtained represents essentially a single location.
APPENDIX E
Applications of Selected Geophysical Methods for Determination of Engineering Parameters Geophysical Method Basic Measurement Application Advantages Limitations Surface Refraction (seismic)
Travel time of compressional waves through subsurface layers Velocity determination of compression wave through subsurface. Depths to contrasting interfaces and geologic correlation of horizontal layers Rapid, accurate, and relatively economical technique.
Interpretation theory generally straightforward and equipment readily available In saturated soils, the compression wave velocity reflects mostly wave velocities in the water, and thus is not indicative of soil properties.
Reflection (seismic)
Travel time of compressional waves reflected from subsurface layers Mapping of selected reflector horizons. Depth determinations, fault detection, discontinuities, and other anomalous features Rapid, thorough coverage of given site area. Data displays highly effective.
In saturated soils, the compression wave velocity reflects mostly wave velocities in the water, and thus is not indicative of soil properties.
Rayleigh wave dispersion Travel time and period of surface Rayleigh waves Inference of shear wave velocity in near-surface materials Rapid technique which uses conventional refraction seismographs Coupling of energy to the ground may be inefficient, restricting extent of survey coverage. Data resolution and penetration capability are frequency-dependent;
sediment layer thickness and/or depth interpretations must be considered approximate.
Vibratory (seismic)
Travel time or wavelength of surface Rayleigh waves Inference of shear wave velocity in near-surface materials Controlled vibratory source allows selection of frequency, hence wavelength and depth of penetration [up to 60 m (200 ft)].
Detects low-velocity zones underlying strata of higher velocity.
Accepted method Coupling of energy to the ground may be inefficient, restricting extent of survey coverage. Data resolution and penetration capability are frequency-dependent;
sediment layer thickness and/or depth interpretations must be considered approximate.
Reflection profiling (seismic-acoustic)
Travel times of compressional waves through water and subsurface materials and amplitude of reflected signal.
Mapping of various lithologic horizons; detection of faults, buried stream channels, and salt domes, location of buried man-made objects; and depth determination of bedrock or other reflecting horizons.
Surveys of large areas at minimal time and cost; continuity of recorded data allows direct correlation of lithologic and geologic changes; correlative drilling and coring can be kept to a minimum.
Data resolution and penetration capability is frequency- dependent; sediment layer thickness and/or depth to reflection horizons must be considered approximate unless true velocities are known; some bottom conditions (e.g., organic sediments) prevent penetration; water depth should be at least 5 to 6 m
(15 to 20 ft) for proper system operation.
Electrical resistivity Electrical resistance of a volume of material between probes Complementary to refraction (seismic). Quarry rock, groundwater, sand and gravel prospecting. River bottom studies and cavity detection.
Economical nondestructive technique. Can detect large bodies of soft materials.
Lateral changes in calculated resistance often interpreted incorrectly as depth related; hence, for this and other reasons, depth determinations can be grossly in error. Should be used in conjunction with other methods, i.e., seismic.
APPENDIX E, Contd.
Geophysical Method Basic Measurement Application Advantages Limitations Surface (Continued)
Acoustic (resonance)
Amplitude of acoustically coupled sound waves originating in an air- filled cavity Traces (on ground surface)
lateral extent of cavities Rapid and reliable method.
Interpretation relatively straightforward. Equipment readily available Must have access to some cavity opening. Still in experimental stage - limits not fully established Ground penetrating radar(GPR)
Travel time and amplitude of a reflected electromagnetic wave Rapidly profiles layering conditions. Stratification, dip, water table, and presence of many types of anomalies can be determined Very rapid method for shallow site investigations. On line digital data processing can yield on site look. Variable density display highly effective Transmitted signal rapidly attenuated by water.
Severely limits depth of penetration. Multiple reflections can complicate data interpretation.
Generally performs poorly in clay-rich sediments.
Gravity Variations in gravitational field Detects anticlinal structures, buried ridges, salt domes, faults, and cavities Provided extreme care is exercised in establishing gravitational references, reasonably accurate results can be obtained Requires specialized personnel. Anything having mass can influence data (buildings, automobiles, etc).
Data reduction and interpretation are complex.
Topography and strata density influence data.
Magnetic Variations of earths magnetic field Determines presence and location of magnetic or ferrous materials in the subsurface. Locates ore bodies Minute quantities of magnetic materials are detectable Only useful for locating magnetic materials.
Interpretation highly specialized. Calibration on site extremely critical. Presence of any ferrous objects near the magnetometer influences data.
Uphole/downhole (seismic)
Vertical travel time of compressional and/or shear waves Velocity determination of vertical P- and/or S-waves.
Identification of low-velocity zones Rapid technique useful to define low- velocity strata. Interpretation straightforward Care must be exercised to prevent undesirable influence of grouting or casing.
Crosshole (seismic)
Horizontal travel time of compressional and/or shear waves Velocity determination of horizontal P- and/or S-waves.
Elastic characteristics of sub- surface strata can be calculated.
Generally accepted as producing reliable results. Detects low- velocity zones provided borehole spacing not excessive.
Careful planning with regard to borehole spacing based upon geologic and other seismic data an absolute necessity. Snells law of refraction must be applied to establish zoning. A borehole deviation survey must be run. Requires highly experienced personnel. Repeatable source required.
Borehole spontaneous potential Natural earth potential Correlates deposits, locates water resources, studies rock deformation, assesses permeability, and determines groundwater salinity.
Widely used, economical tool.
Particularly useful in the identification of highly porous strata (sand, etc.).
Log must be run in a fluid filled, uncased boring. Not all influences on potentials are known.
APPENDIX E, Contd.
Geophysical Method Basic Measurement Application Advantages Limitations Borehole (Continued)
Single-point resistivity Strata electrical resistance adjacent to a single electrode In conjunction with spontaneous potential, correlates strata and locates porous materials Widely used, economical tool. Log obtained simultaneous with spontaneous potential Strata resistivity difficult to obtain. Log must be run in a fluid filled, uncased boring. Influenced by drill fluid.
Long and short- normal resistivity Near-hole electrical resistance Measures resistivity within a radius of 40 to 165 cm (16 to
64 in.)
Widely used, economical tool Influenced by drill fluid invasion. Log must be run in a fluid filled, uncased boring.
Lateral resistivity Far-hole electrical resistance Measures resistivity within a radius of 6 m (20 ft)
Less drill fluid invasion influence Log must be run in a fluid filled, uncased boring.
Investigation radius limited in low moisture strata.
Induction resistivity Far-hole electrical resistance Measures resistivity in air- or oil-filled holes Log can be run in a nonconductive casing Large, heavy tool.
Borehole imagery (acoustic)
Sonic image of borehole wall Detects cavities, joints, fractures in borehole wall.
Determines attitude (strike and dip) of structures.
Useful in examining casing interior. Graphic display of images. Fluid clarity immaterial.
Highly experienced operator required. Slow log to obtain. Probe awkward and delicate.
Continuous sonic
(3-D) velocity Time of arrival of P-
and S-waves in high- velocity materials Determines velocity of P- and S-waves in near vicinity of borehole. Potentially useful for cavity and fracture detection. Modulus determinations. Sometimes S-wave velocities are inferred from P-wave velocity .
Widely used method. Rapid and relatively economical. Variable density display generally impressive. Discontinuities in strata detectable Shear wave velocity definition questionable in unconsolidated materials and soft sedimentary rocks.
Only P-wave velocities greater than 1500 m/s (5,000
ft/s) can be determined.
Natural gamma radiation Natural radioactivity Lithology, correlation of strata, may be used to infer permeability. Locates clay strata and radioactive minerals.
Widely used, technically simple to operate and interpret.
Borehole effects, slow logging speed, cannot directly identify fluid, rock type, or porosity. Assumes clay minerals contain potassium-40 isotope.
APPENDIX E, Contd.
Geophysical Method Basic Measurement Application Advantages Limitations Borehole (Continued)
Gamma-gamma density Electron density Determines rock density of subsurface strata.
Widely used. Can be applied to quantitative analyses of engineering properties. Can provide porosity.
Borehole effects, calibration, source intensity, chemical variation in strata affect measurement precision. Radioactive source hazard.
Neutron porosity Hydrogen content Moisture content (above water table), total porosity (below water table)
Continuous measurement of porosity. Useful in hydrology and engineering property determinations. Widely used Borehole effects, calibration, source intensity, bound water, all affect measurement precision. Radioactive source hazard.
Neutron activation Neutron capture Concentration of selected radioactive materials in strata Detects elements such as U, Na, Mn. Used to determine oil-water contact (oil industry) and in prospecting for minerals (Al, Cu)
Source intensity, presence of two or more elements having similar radiation energy affect data.
Borehole magnetic Nuclear precession Deposition, sequence, and age of strata Distinguishes ages of lithologically identical strata Earth field reversal intervals under study. Still subject of research.
Mechanical caliper Diameter of borehole Measures borehole diameter Useful in a wet or dry hole Must be recalibrated for each ru
n. Averages
3 diameters.
APPENDIX E, Contd.
Geophysical Method Basic Measurement Application Advantages Limitations Borehole (Continued)
Acoustic caliper Sonic ranging Measures borehole diameter.
Large range. Useful with highly irregular shapes Requires fluid filled hole and accurate positioning.
Temperature Temperature Measures temperature of fluids and borehole sidewalls.
Detects zones of inflow or fluid loss .
Rapid, economical, and generally accurate None of importance.
Fluid resistivity Fluid electrical resistance Water-quality determinations and auxiliary log for rock resistivity.
Economical tool Borehole fluid must be same as groundwater.
Tracers Direction of fluid flow Determines direction of fluid flow.
Economical Environmental considerations often preclude use of radioactive tracers.
Flowmeter Fluid velocity and quantity Determines velocity of subsurface fluid flow and, in most cases, quantity of flow.
Interpretation is simple.
Impeller flowmeters usually cannot measure flows less than 1 to 1.7 cm/s (2 - 3 ft/min).
Borehole dipmeter Sidewall resistivity Provides strike and dip of bedding planes. Also used for fracture detection.
Useful in determining information on the location and orientation of primary sedimentary structures over a wide variety of hole conditions.
Expensive log to make. Computer analysis of information needed for maximum benefit.
Downhole flow meter Flow across the borehole Determines the rate and direction of groundwater flow A reliable, cost effective method to determine lateral foundation leakage under concrete structures Assumes flow not influenced by emplacement of borehole.
APPENDIX F
IN SITU TESTING METHODS
Table F-1 In Situ Tests for Rock and Soil (adapted from EM 1110-1-1804, Department of the Army, 1984)
Applicability to Purpose of Test Type of Test Soil Rock Shear strength Standard penetration test (SPT)
Field vane shear Cone penetrometer test (CPT)
Direct shear Plate bearing or jacking Borehole direct shearb Pressuremeterb Uniaxial compressiveb Borehole jackingb X
X
X
X
X
X
Xa X
X
X
Bearing capacity Plate bearing Standard penetration X
X
Xa Stress conditions Mass deformability Hydraulic fracturing Pressuremeter Overcoring Flatjack Uniaxial (tunnel) jacking Borehole jackingb Chamber (gallery) pressureb Geophysical (refraction)
Pressuremeter or dilatometer Plate bearing Standard penetration Uniaxial (tunnel) jacking Borehole jackingb Chamber (gallery) pressureb X
X
X
X
X
X
X
X
X
Xa X
X
X
X
X
X
Xa X
X
X
X
Relative density Liquefaction susceptibility Standard penetration In situ sampling Standard penetration Cone penetration test (CPT)
Shear wave velocity (vs)
X
X
X
X
X
a Primarily for clay shales, badly decomposed, or moderately soft rocks, and rock with soft seams.
b Less frequently used.
APPENDIX F, Contd.
Table F-2 In Situ Tests to Determine Shear Strength (adapted from EM 1110-1-
1804, Department of the Army, 1984)
Test For Remarks Soils Rocks Standard penetration X
Use as index test only for strength. Develop local correlations. Unconfined compressive strength in tsf is often 1/6 to 1/8 of N-value Direct shear X
X
Expensive; use when representative undisturbed samples cannot be obtained Field vane shear X
Use strength reduction factor Plate bearing X
X
Evaluate consolidation effects that may occur during test Uniaxial compression X
Primarily for weak rock; expensive since several sizes of specimens must be tested Cone penetration test (CPT)
X
Consolidated undrained strength of clays; requires estimate of bearing factor, Nc Table F-3 In Situ Tests to Determine Stress Conditions (adapted from EM 1110-1-
1804, Department of the Army, 1984)
Test Soils Rocks Remarks Hydraulic fracturing X
Only for normally consolidated or slightly consolidated soils Hydraulic fracturing X
Stress measurements in deep holes for tunnels Vane shear X
Only for recently compacted clays, silts and fine sands (see Blight, 1974, for details and limitations)
Overcoring techniques X
Usually limited to shallow depth in rock Flatjacks X
Uniaxial (tunnel) jacking X
X
May be useful for measuring lateral stresses in clay shales and rocks, also in soils Blight , G.E. Indirect Determination of in Situ Stress Ratios in Particulate Materials, Proceedings of a Speciality Conference, Subsurface Explorations for Underground Excavation and Heavy Construction. American Society of Civil Engineers, New York,
1974.
APPENDIX F, Contd.
Table F-4 In Situ Tests to Determine Deformation Characteristics (adapted from EM 1110-1-1804, Department of the Army,
1984)
Test For Remarks Soils Rocks Geophysical refraction, Cross-hole and downhole X
X
For determining dynamic Youngs Modulus, E, at the small strain induced by test procedure. Test values for E must be reduced to values corresponding to strain levels induced by structure or seismic loads.
Pressuremeter X
X
Consider test as possibly useful but not fully evaluated. For soils and soft rocks, shales, etc.
Chamber test X
X
Uniaxial (tunnel)
jacking X
X
Flatjacking X
Borehole jack or dilatometer X
Plate bearing X
Plate bearing Standard penetration X
X
Used in empirical correlations to estimate settlement of footings; a number of relationships are published in the literature to relate penetration test blow counts to settlement potential.
APPENDIX G
Instruments for Measuring Groundwater Pressure Instrument Type Advantages Limitations1a Observation well Can be installed by drillers without participation of geotechnical personnel.
Provides undesirable vertical connection between strata and is therefore often misleading; should rarely be used.
Open standpipe piezometer Reliable. Long successful performance record.
Self-de-airing if inside diameter of standpipe is adequate.
Integrity of seal can be checked after installation. Can be converted to diaphragm piezometer. Can be used for sampling groundwater. Can be used to measure permeability.
Long time lag. Subject to damage by construction equipment and by vertical compression of soil around standpipe. Extension of standpipe through embankment fill interrupts construction and causes inferior compaction. Porous filter can plug owing to repeated water inflow and outflow. Push-in versions subject to several potential errors.
Twin-tube hydraulic piezometer Inaccessible components have no moving parts. Reliable.
Long successful performance record. When installed in fill, integrity can be checked after installation. Piezometer cavity can be flushed. Can be used to measure permeability.
Application generally limited to long-term monitoring of pore water pressure in embankment dams. Elaborate terminal arrangements needed. Tubing must not be significantly above minimum piezometric elevation. periodic flushing may be required. Attention to many details is necessary.
Pneumatic piezometer Short time lag. Calibrated part of system accessible.
Minimum interference to construction: level of tubes and readout independent of level of tip. No freezing problems.
Attention must be paid to many details when making selection.
Push-in versions subject to several potential errors.
Vibrating wire piezometer Easy to read. Short time lag. Minimum interference to construction: level of lead wires and readout independent of level of tip. Lead wire effects minimal. Can be used to read negative pore water pressures. No freezing problems.
Special manufacturing techniques required to minimize zero drift.
Need for lightning protection should be evaluated. Push-in version subject to several potential errors.
Unbonded electrical resistance piezometer Easy to read. Short time lag. Minimum interference to construction: level of lead wires and readout independent of level of tip. Can be used to read negative pore water pressures. No freezing problems. Provides temperature measurement. Some types suitable for dynamic measurements.
Low electrical output. Lead wire effects. Errors caused by moisture and electrical connections are possible. Need for lightning protection should be evaluated.
a Diaphragm piezometer readings indicate the head above the piezometer, and the elevation of the piezometer must be measured or estimated if piezometric elevation is required. All diaphragm piezometers, except those provided with a vent to the atmosphere, are sensitive to barometric pressure changes.
APPENDIX G, Contd.
Instrument Type Advantages Limitationsa Bonded electrical resistance piezometer Easy to read. Short time lag. Minimum interference to construction: level of lead wires and readout independent of level of tip. Suitable for dynamic measurements. Can be used to read negative pore water pressures. No freezing problems.
Low electrical output. Lead wire effects. Errors caused by moisture, temperature, and electrical connections are possible. Long-term stability uncertain. Need for lightning protection should be evaluated.
Push-in version subject to several potential errors.
Multipoint piezometer, with packers Provides detailed pressure-depth measurements.
Can be installed in horizontal or upward boreholes.
Other advantages depend on type of piezometer: see above in table.
Limited number of measurement points. Other limitations depend on type of piezometer: see above in table.
Multipoint piezometer, surrounded with grout Provides detailed pressure-depth measurements.
Simple installation procedure. Other advantages depend on type of piezometer: See above in table.
Limited number of measurement points. Applicable only in uniform clay of known properties. Difficult to ensure in-place grout of known properties. Other limitations depend on type of piezometer: see above in table.
Multipoint push-in piezometer Provides detailed pressure-depth measurements.
Simple installation procedure. Other advantages depend on type of piezometer: See above in table.
Limited number of measurement points. Subject to several potential errors. Other limitations depend on type of piezometer: see above in table.
Multipoint piezometer, with movable probe Provides detailed pressure-depth measurements.
Unlimited number of measurement points. Allows determination of permeability. Calibrated part of system accessible. Great depth capability.
Westbay Instruments system can be used for sampling groundwater and can be combined with inclinometer casing.
Complex installation procedure. Periodic manual readings only.
REGULATORY ANALYSIS
A separate regulatory analysis was not prepared for this regulatory guide. The regulatory analysis prepared for Draft Regulatory Guide DG-1101, Site Investigations for Foundations of Nuclear Power Plants (February 2001), provides the regulatory basis for this regulatory guide as well. DG-1101 was issued for public comment as the draft of this present regulatory guide. A
copy of the regulatory analysis is available for inspection and copying for a fee at the U.S.
Nuclear Regulatory Commission Public Document Room, 11555 Rockville Pike, Rockville, MD; the PDRs mailing address is USNRC PDR, Washington, DC 20555; telephone (301)415-
4737 or 1-(800)397-4209; fax (301)415-3548; e-mail <PDR@NRC.GOV>.