DB/T 8.2-2020Specification for the construction of seismic station - Crustal deformation station - Part 2: Crustal tilt and strain observatory in borehole (English PDF)

4.1 Requirements for basic working conditions

4.1.1 It shall have continuous and stable power supply conditions and meet the requirements of instrument operation.

4.1.2 It shall have continuous and stable communication conditions and meet the data transmission requirements.

4.1.3 The conditions for safety protection shall be met.

4.1.4 It is advisable to have convenient transportation to meet the needs of timely maintenance.

4.2 Geological structure requirements

4.2.1 The observation site should be selected on both sides of the active fault zone, but the fault fracture zone should be avoided.

4.2.2 The stratum dip angle should not be greater than 40°, the rock mass is complete, and the rock structure is uniform and compact.

4.2.3 The abnormally high temperature area of geothermal should be avoided.

4.2.4 Should avoid the strong Jingliu area of groundwater.

4.2.5 Should avoid underground karst development areas.

4.3 Observation environment requirements

4.3.1 The observation site should avoid alluvial fans, alluvial fans, flash flood channels, vents, and areas vulnerable to lightning strikes.

4.3.2 Development planning areas that have an impact on borehole ground tilt and borehole strain observation should be avoided.

4.3.3 The technical indicators of the observation environment of the borehole ground tilt station shall meet the requirements of 4.1 in GB/T 19531.3-2004; the borehole ground strain station the technical indicators of the observation environment of the station shall comply with the provisions of 4.2 in GB/T 19531.3-2004.

4.3.4 The distance between the observation site and various sources of interference should comply with the provisions in Chapter 5 of GB/T 19531.3-2004.

4.3.5 The test method for the comprehensive interference of the observation environment shall be implemented in accordance with the provisions of Appendix C in GB/T 19531.3-2004.

4.4 Comprehensive observation requirements

4.4.1 It is advisable to conduct co-site comprehensive observations with seismic measurements, gravity, global navigation satellite system reference station observations (GNSS), fault deformation, and static water level.

4.4.2 The observation site should be equipped with three elements of meteorological auxiliary observation.

5.1 Requirements for hole formation

5.1.1 See Appendix A for the overall composition design of the borehole.

5.1.2 The full-hole core mining rate should not be less than 70%.

5.1.3 The tightness test of the borehole should be carried out.

5.2 Basic indicators

5.2.1 The inclination of the borehole should not be greater than 1°.

5.2.2 The aperture should comply with the requirements of 4.2.12 in DB/T 31.1-2008 and 4.2.11 in DB/T 31.2-2008.

5.2.3 The drilling depth should not be less than 30m.

DB/T 8.2-2020

5.3 Measurement section

5.3.1 It should be ensured that the base rock of the measuring section where the probe is installed is complete, avoiding rock fracture sections, rock veins, lenses, and water-rich layers.

5.3.2 Core mining should be continuous.

5.3.3 In accordance with the provisions of 2.9 in GB/T 50266-2013, the rock core in the measurement section shall be subjected to a rock compression deformation test to measure the rock bullet Parameters such as modulus and Poisson's ratio.

5.4 Casing

5.4.1 Standard sealing casing should be installed from the surface to the bedrock, and the casing should not be less than 1m embedded in the bedrock.

5.4.2 Cement slurry should be poured between the casing and the hole wall and treated with slurry turning.

5.5 Drilling the ground

5.5.1 A cement well platform should be built around the casing of the borehole, and a well cover with a lock should be added. The well cover should be marked with drilling and instrument information;

See Appendix B for the design.

5.5.2 The ground around the borehole should be imperviously treated, and the treated area should not be less than 4m×4m.

5.5.3 No building shall be built above the borehole.

7.1 Main observation equipment

7.1.1 Borehole tilt meter

The technical indicators and functional requirements of the borehole inclinometer should conform to Chapter 4 of DB/T 31.1-2008 and Chapter 4 of DB/T 45-2012.

The provisions of Chapter 4: The data output rate of the data collector should not be less than 1 sps (sampler sample, the number of samples per second);

The Ministry should have lightning protection measures.

7.1.2 Borehole strain gauge

The technical indicators and functional requirements of the borehole strain gauges shall comply with Chapter 4 of DB/T 31.2-2008 and Chapter 4 of DB/T 54-2013.

The provisions of Chapter 4: The data output rate of the data collector should not be less than 1 sps; there should be lightning protection measures inside the probe of the instrument; spare sensors should be equipped.

7.2 Auxiliary observation equipment in borehole

The borehole should be equipped with barometers, thermometers and water level gauges as specified in Table 1.

DB/T 8.2-2020

8.1 Equipment installation

8.1.1 The borehole inclinometer, borehole strain gauge and other auxiliary equipment should follow the installation requirements and steps in the instrument manual installation.

8.1.2 When installing the instrument, the installation unit should fill in the instrument installation record form. For the content and requirements of the instrument installation record form, see Appendix D.

8.1.3 The thermometer in the borehole should be the same as the depth of the probe of the main observation instrument.

8.2 Trial run

8.2.1 After the installation of the instrument is completed, a trial run of not less than six months should be carried out.

8.2.2 The integrity rate of the observation data during the trial operation should not be less than 95%.

8.2.3 The data quality of the last month of trial operation shall meet the following requirements.

a) The error and relative noise level in the M2 wave tidal factor of the borehole tilt observation data should meet the requirements of 6.3.1 in DB/T 40.1-2010.The Venedikov harmonic analysis method should be used to calculate the error in the tidal factor, and the Chebyshev polynomial fitting method should be used to calculate the relative noise level, refer to Appendix G in DB/T 45-2012 for the calculation method.

b) The error in the M2 wave tidal factor of the borehole body strain observation data should meet the requirements of 7.3.1 in DB/T 40.1-2010.The Vendikov harmonic analysis method should be used to calculate the error in the tide factor. For the calculation method, refer to the appendix in DB/T 54-2013.

Record A.

c) The error in the M2 wave tide factor of the borehole four-component strain observation data should meet the requirements of 7.3.1 in DB/T 40.1-2010, and the self-check reliability of the observation data should not be less than 0.7.The Vendikov harmonic analysis method should be used to calculate the error in the tide factor, refer to Appendix A in DB/T 54-2013 for the calculation method; refer to Appendix A in DB/T 54-2013 for the calculation method of self-check reliability.

Record B.

9.1 Basic requirements

After the construction of the station is completed, the observation site and drill hole selection report, drill hole construction report, measurement section lithology test report, instrument installation Reports, station trial operation reports, land use conditions and other materials are archived in accordance with the file management requirements of the competent unit.

9.2 Observation site and borehole survey selection report

The observation site and borehole survey report should include the following.

a) The geographical location and administrative territory of the observation site;

b) Survey and selection unit, survey and selection process, survey and selection method, and main survey and selection personnel;

c) The stratum lithology, geological structure, hydrogeology, topography and natural environment of the observation site;

DB/T 8.2-2020

d) Regional geological structure map and topographic map of the observation site;

e) For the selection of boreholes, it is advisable to conduct geophysical exploration on the observation site to pre-detect the integrity of underground aquifers and rocks;

f) The interference source situation around the borehole;

g) Pictures selected on site;

h) Comprehensive evaluation and conclusion of observation site and borehole survey selection.

9.3 Drilling construction report

9.3.1 The drilling construction report shall include the following contents.

a) Logging histogram;

b) Drilling construction unit, construction design, construction overview, construction equipment, construction personnel, and construction time;

c) Drilling construction process and site photos;

d) Description of rock tightness test;

e) Casing installation process and on-site photos;

f) The core preservation measures should be numbered according to the order of taking cores, photographed, and the cores and photos should be properly preserved;

g) Quality evaluation methods and conclusions of boreholes.

9.3.2 The logging histogram should include the following.

a) The latitude and longitude of the borehole location (accurate to 0.001°);

b) The magnetic declination of the drilling position (accurate to 0.1°);

c) The diameter of each well section (accurate to 0.1mm);

d) Logging inclination of each well section (accurate to 0.1°);

e) Drilling depth (accurate to 0.1m);

f) Lithology description of each layer;

g) The rock integrity of the measurement section.

9.4 Lithology test report of the measurement section

The lithology test report of the measurement section should include the following.

a) Description of rock compression deformation test;

b) Test process;

c) Test results.

9.5 Instrument installation report

The instrument installation report should include the following.

a) Installation unit, assisting unit, installation time and installation personnel;

b) Introduction to stations and boreholes;

c) Description of instruments and auxiliary observation equipment;

d) Description of special lightning protection measures for instrument probes;

e) Taking the borehole as the center, the spatial scope is 500m×500m (scale not less than 1.2000) and 5km×5km (scale the scale is not less than 1.2000) satellite map;

f) The water level of the borehole should be explained whether it is a dry hole;

g) The installation process and on-site pictures shall include an explanation of the centering degree of the instrument probe installation;

h) The borehole component strain gauge and borehole inclinometer should give the true azimuth angle of each component and explain the positioning method. If the compass is used for positioning, it should be attached photo;

i) Instrument network parameters;

DB/T 8.2-2020

j) Installation conclusion;

k) Instrument installation record sheet.

9.6 Station trial operation report

The station trial operation report should include the following.

a) Introduction to the basic situation of stations and boreholes;

b) Instrument and installation status;

c) The operation of the instrument;

d) Main observation and auxiliary observation curves;

e) Data quality during trial operation;

f) Conclusion of trial operation.

9.7 Land use

DB/T 8.2-2020

Appendix A

(Informative appendix) Design example of overall structure of drilling

Figure A. 1 gives an example of the overall structure design of drilling.

Figure A. 1 Design drawing of drilling overall structure

DB/T 8.2-2020

Appendix B

(Informative appendix) Design example of borehole cover and manhole cover information B. 1 Design example of borehole cover

Figure B. 1 gives an example of borehole cover design.

Unit is mm

Figure B. 1 Design drawing of borehole cover

B. 2 Example of design of borehole tilt observation well cover information

Figure B. 2 gives an example of information design of borehole tilt observation well cover.

Figure B. 2 Information design drawing of borehole tilt observation well cover

DB/T 8.2-2020

B. 3 Design example of borehole component strain observation well cover information

Figure B. 3 gives an example of borehole component strain observation well cover information design.

Figure B. 3 Design drawing of borehole component strain observation well cover information

B. 4 Example of design of borehole volume strain observation well cover information

Figure B. 4 gives an example of information design of borehole body strain observation well cover.

DB/T 8.2-2020

Figure B. 4 Borehole volume strain observation well cover information design drawing

DB/T 8.2-2020

Appendix C

(Informative appendix)

Example of recording room design

Figure C. 1 gives an example of recording room design.

Unit is mm

Figure C. 1 Design drawing of the recording room

DB/T 8.2-2020

Appendix D

(Normative appendix) Instrument installation record sheet the instrument installation record table is shown in Table D. 1.