NB/T 10107-2018Specification for geotechnical tests of offshore wind power projects (English PDF)

Foreword

This document was issued on 25 December 2018 by the National Energy Administration of the PRC and takes effect on 1 May 2019.

It is a NB/T standard: recommended rather than compulsory, but it is the text a Chinese reviewer applies when assessing a submission.

It is classified under ICS 27.180, Chinese classification P 61.

This specification has been prepared in accordance with the requirements of the "Notice of the National Energy Administration on Issuing the Second Batch of Plans for the Formulation (Revision) of Industry Standards in the Energy Sector for the Year 2014" (Guo Neng Ke Ji [2015] No. 12).

In preparing the specification, the drafting group carried out extensive investigation and research, carefully summarized practical engineering experience, referred to relevant international standards and to advanced foreign standards, and completed the text on the basis of a wide solicitation of comments.

The main technical content of this specification comprises: preparation and saturation of specimens; physical property tests of soil; mechanical property tests of soil; in-situ tests; water quality analysis; soil quality analysis; clay minerals analysis; submarine shallow gas and gassy soil tests; and physical and mechanical property tests of rock.

The specification is administered by the National Energy Administration. It was proposed by, and is under the day-to-day management of, the China Renewable Energy Engineering Institute (Hydropower and Water Resources Planning and Design General Institute).

Interpretation of the specific technical content is the responsibility of the Sub-Technical Committee for Wind Farm Planning and Design of the Wind Power Standardization Technical Committee of the Energy Industry.

Comments and suggestions arising during the implementation of this specification should be addressed to the China Renewable Energy Engineering Institute, No. 2 Liupukang Beixiaojie, Xicheng District, Beijing, postcode 100120.

Chief editing organization: PowerChina Huadong Engineering Corporation Limited.

Participating organizations: Zhejiang Huadong Construction Engineering Co., Ltd.; Zhejiang Huadong Engineering Safety Technology Co., Ltd.; Hohai University; Changjiang River Scientific Research Institute of the Changjiang Water Resources Commission; Wuhan University; Nanjing University; and the Institute of Rock and Soil Mechanics of the Chinese Academy of Sciences.

The chief editing department for the specification is the China Renewable Energy Engineering Institute (Hydropower and Water Resources Planning and Design General Institute); the approving department is the National Energy Administration; the date of implementation is 1 May 2019.

The specification carries the industry standard designation NB/T 10107-2018 and the filing (registration) number J2649-2019, and was published by China Water and Power Press, Beijing, 2019.

The published document lists the principal drafters and the principal reviewers of the specification by name; those name lists are not reproduced here.

Appendices and Supplementary Material

Appendix A, Test Methods for Physical and Mechanical Indexes of Rock and Soil in Offshore Wind Power Projects, page 172, tabulates the test method to be adopted for each physical and mechanical index.

Appendix B, Requirements and Managements of Soil Samples, page 176, sets out the requirements for soil samples and their management.

Appendix C, Test Record Forms, page 179, is the longest appendix, running to page 207, and provides the standard record forms for the tests of the specification.

Appendix D, Parameter Calculation for Hollow Cylinder Dynamic Torsional Shear Test, page 208, gives the parameter calculations for the test of Section 6.13.

Appendix E, Identification Standard for Clay Minerals by SEM, page 212, gives the identification criteria for clay minerals under the scanning electron microscope.

Explanation of Wording in This Specification, page 214, defines the degrees of obligation attached to the auxiliary verbs used in the text.

List of Quoted Standards, page 215, lists the standards referred to normatively.

Addition: Explanation of Provisions, page 217, is the separately paginated commentary explaining the intent of the individual provisions; it extends the document well beyond page 217.

Scope of Application and Structure

The specification is a code of practice (gui cheng) for the geotechnical testing carried out in support of the survey, design and construction of offshore wind farm projects.

It covers the whole chain of geotechnical testing: sample and specimen handling (Chapter 4), laboratory physical and mechanical testing of soil (Chapters 5 and 6), in-situ testing from a marine platform or vessel (Chapter 7), chemical and mineralogical characterization of water and soil (Chapters 8 to 10), the specific hazard of submarine shallow gas and gassy soils (Chapter 11) and rock testing (Chapter 12).

The body of the specification runs to 171 numbered pages, followed by five appendices to page 213, the wording explanation, the list of quoted standards, and the explanation of provisions from page 217 onwards.

The front matter is numbered in roman numerals: the foreword occupies pages III and IV, the Chinese table of contents pages V to VIII, and the English table of contents pages IX to XII.

The document carries an official English title on its cover, Specification for Geotechnical Tests of Offshore Wind Power Projects, and an official English table of contents, both reproduced here as printed.

The English cover title agrees with the Chinese title; no discrepancy between the two was found.

1 Scope

NB/T 10107-2018 sets out how soil and rock samples taken at an offshore wind farm are tested, and how the results are reported so that a foundation designer can rely on them. Offshore geotechnical testing is not the same problem as onshore: samples arrive disturbed by a long journey, the soils are frequently soft marine clays and carbonate sands, and the loading that matters is cyclic - wave and wind acting on a monopile or jacket for twenty-five years. The specification therefore fixes sample handling, storage and preparation from the moment a core reaches the vessel, then works through the laboratory programme: physical property tests, particle size and Atterberg limits, density and moisture content, consolidation and permeability, direct shear and triaxial testing in its various drainage conditions, unconfined compression, vane shear, and the dynamic and cyclic tests - resonant column, cyclic triaxial and cyclic simple shear - used to derive stiffness degradation, damping and liquefaction resistance. Rock testing is covered in its own right, with uniaxial and triaxial compression, tensile and shear strength, and durability. In-situ testing and its correlation with laboratory results are addressed alongside. For each test the specification gives the apparatus and its calibration, the specimen preparation, the procedure, the calculations, and the form the result takes in the report. It applies to the survey, design and construction stages of offshore and intertidal wind power projects in China.

1.0.1 This specification has been formulated in order to standardize the work content and the technical requirements of geotechnical testing for offshore wind power projects, and to ensure the quality of the testing work and the quality of its results.

1.0.2 This specification is applicable to the geotechnical tests of offshore wind power projects.

1.0.3 In addition to complying with this specification, geotechnical testing for offshore wind power projects shall also comply with the provisions of the relevant current national standards.

The provisions of Chapter 1 are drafted in the three-level clause numbering style (1.0.1, 1.0.2, 1.0.3) that is customary for Chinese engineering codes of practice (gui cheng), rather than in the clause style of a product standard.

The document is issued as an energy industry standard of the People's Republic of China under the code NB/T 10107-2018, with ICS classification 27.180 and Chinese standard classification code P 61.

2 Terms and Symbols

Chapter 2 is divided into two sections: 2.1 Terms, beginning on page 2, and 2.2 Symbols, beginning on page 3.

Section 2.1 establishes the defined vocabulary used throughout the specification for offshore geotechnical testing.

Section 2.2 establishes the letter symbols used for the measured quantities, indexes and calculation parameters that appear in the test procedures and formulae of the following chapters.

Together the two sections occupy pages 2 to 4 of the standard, immediately before the basic requirements of Chapter 3.

3 Basic Requirements

Chapter 3, beginning on page 5, sets out the basic requirements governing geotechnical testing work for offshore wind power projects.

The chapter is not subdivided into numbered sections; it is presented as a single body of general provisions applying to all the test methods of the specification.

Its provisions precede, and therefore govern, the specimen handling requirements of Chapter 4 and all of the laboratory and in-situ test chapters that follow.

4 Preparation and Saturation of Specimen

Chapter 4 covers the preparation and the saturation of test specimens and runs from page 6 to page 18.

4.1 General Requirements, page 6, states the requirements common to all specimen preparation and saturation operations.

4.2 Specimen Preparation, page 6, is the longest section of the chapter and covers the preparation of specimens for the subsequent physical and mechanical tests.

4.3 Specimen Saturation, page 15, covers the saturation of prepared specimens before testing.

The requirements for the taking, handling and management of the soil samples that feed this chapter are given separately in Appendix B, Requirements and Managements of Soil Samples, page 176.

Blank record forms for the operations of this and the following chapters are collected in Appendix C, Test Record Forms, page 179.

5 Physical Property Tests of Soil

Chapter 5, pages 19 to 24, specifies nine physical property tests of soil.

5.1 Water Content Test, page 19.

5.2 Density Test, page 19.

5.3 Grain Size Analysis Test, page 19.

5.4 Atterberg Limit Test, page 20 (limit water content test in the Chinese text).

5.5 Specific Gravity Test of Soil Grain, page 20.

5.6 Relative Density Test, page 20.

5.7 Compaction Test, page 20.

5.8 Thermal Conductivity Test, page 21, which occupies three pages and is one of the two physical tests treated at length.

5.9 Specific Surface Test, page 24.

The short treatment given to the classical index tests (water content, density, grain size, plasticity limits, specific gravity) reflects the fact that these follow established national test procedures; the specification concentrates its detailed text on the tests that are specific to the offshore environment, such as thermal conductivity and specific surface.

6 Mechanical Property Test of Soil

Chapter 6, pages 25 to 86, is the largest chapter of the specification and specifies fifteen mechanical property tests of soil, including a full set of dynamic tests.

6.1 One-Dimensional Compression Test, page 25.

6.2 Direct Shear Test, page 32.

6.3 Residual Shear Strength Test, page 35.

6.4 Soil-Steel Pile Interface Behaviour Test, page 39, a test specific to offshore foundations bearing on driven steel piles.

6.5 Permeability Test, page 41.

6.6 Triaxial Compression Test, page 42, which occupies nine pages.

6.7 Unconfined Compressive Strength Test, page 51.

6.8 Triaxial Creep Test, page 51.

6.9 True Triaxial Test, page 53.

6.10 Dynamic Triaxial Test, page 59.

6.11 Dynamic Simple Shear Test, page 65.

6.12 Resonant Column Test, page 69.

6.13 Hollow Cylinder Dynamic Torsional Shear Test, page 75, whose parameter calculation is developed in Appendix D, page 208.

6.14 Miniature Vane Shear Test, page 83.

6.15 Pocket Penetrometer Test, page 84.

The presence of five dynamic tests (dynamic triaxial, dynamic simple shear, resonant column, hollow cylinder torsional shear and the cyclic interface test) reflects the cyclic loading regime imposed on offshore wind turbine foundations by wind, wave and current action.

7 In-Situ Tests

Chapter 7, pages 87 to 125, specifies thirteen in-situ test methods.

7.1 Cone Penetration Test, page 87, which occupies eight pages and is the most extensively treated in-situ method.

7.2 T-bar Penetration Test, page 95, a full-flow penetrometer method used in soft marine clays.

7.3 Ball Penetration Test, page 97, the second full-flow penetrometer method.

7.4 Vane Shear Test, page 99.

7.5 Standard Penetration Test, page 101.

7.6 Dynamic Penetration Test, page 103.

7.7 Pressuremeter Test, page 104.

7.8 Flat Dilatometer Test, page 109.

7.9 In-Situ Loading Test, page 113.

7.10 In-Situ Direct Shear Test, page 113.

7.11 Borehole Jack Test, page 113.

7.12 Wave Velocity Test, page 117.

7.13 Resistivity Test, page 122.

Sections 7.9 to 7.11 share the same opening page, which indicates that these three rock and soil loading tests are treated briefly by cross reference rather than in full detail.

8 Water Quality Analysis

Chapter 8, pages 126 to 138, specifies eleven determinations for the chemical analysis of water, aimed principally at assessing the corrosivity of sea water and pore water towards steel and concrete structures.

8.1 pH Value, page 126.

8.2 Calcium Ion and Magnesium Ion, page 130.

8.3 Chlorion Ion, page 130 (chloride ion in the Chinese text).

8.4 Sulfate Ion, page 133.

8.5 Free Carbon Dioxide, page 134.

8.6 Corrosive Carbon Dioxide, page 134.

8.7 Ammonium Ion, page 134.

8.8 Alkalinity, page 135.

8.9 Potassium Ion and Sodium Ion, page 135.

8.10 Total Salinity, page 136.

8.11 Sulfate Reducing Bacteria, page 136, a microbiological determination relevant to microbially induced corrosion of submerged steelwork.

9 Soil Quality Analysis

Chapter 9, pages 139 to 154, specifies six determinations for the chemical characterization of soil.

9.1 pH Value, page 139.

9.2 Chemical Composition of Soluble Salt, page 140 (easily soluble salt in the Chinese text).

9.3 Chemical Composition of Soil, page 141, covering the total chemical composition and occupying six pages.

9.4 Oxidation-Reduction Potential, page 147.

9.5 Corrosion Current Density, page 148.

9.6 Organic Matter Test, page 149.

As in Chapter 8, the emphasis of the chapter is on the parameters that control the corrosion of buried and submerged foundation elements: redox potential, corrosion current density and soluble salt content.

10 Clay Minerals Analysis

Chapter 10, pages 155 to 157, specifies three mineralogical analysis methods for clay.

10.1 X-ray Diffraction Analysis, page 155.

10.2 Differential Thermal Analysis, page 155.

10.3 Scanning Electron Microscopy Analysis, page 156.

The identification criteria to be applied to the scanning electron microscope images are given in Appendix E, Identification Standard for Clay Minerals by SEM, page 212.

11 Submarine Shallow Gas and Gassy Soil Tests

Chapter 11, pages 158 to 162, deals with submarine shallow gas and with gassy soils, a hazard specific to offshore construction.

11.1 Submarine Shallow Gas Test, page 158, covering the detection and testing of shallow gas in the sea bed.

11.2 Mechanical Property Test of Submarine Gassy Soil, page 161, covering the mechanical behaviour of soils containing free gas.

This chapter has no counterpart in the general onshore geotechnical testing codes and is one of the distinguishing features of the specification.

12 Physical and Mechanical Property Tests of Rock

Chapter 12, pages 163 to 171, specifies nine physical and mechanical property tests of rock.

12.1 Water Content Test, page 163.

12.2 Water Absorption Test, page 163.

12.3 Grain Density Test, page 163.

12.4 Bulk Density Test, page 163 (block density in the Chinese text).

12.5 Swelling Test, page 164.

12.6 Uniaxial Compressive Strength Test, page 164.

12.7 Uniaxial Compressive Deformability Test, page 165.

12.8 Direct Shear Strength Test, page 168; the Chinese heading for this section reads simply direct shear test.

12.9 Point-Load Strength Test, page 171.

The four index tests 12.1 to 12.4 share a single opening page and are therefore treated in condensed form, while the strength and deformability tests are developed in full.