NB/T 10388-2020Code for engineering geological investigation of tidal power projects (English PDF)

Foreword

This document was issued on 23 October 2020 by the National Energy Administration of the PRC and takes effect on 1 February 2021.

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 27.140, Chinese classification P 61.

This code has been prepared in accordance with the requirements of the Notice of the National Energy Administration on Issuing the First Batch of the 2014 Plan for the Formulation and Revision of Industry Standards in the Energy Sector (Guo Neng Ke Ji [2014] No. 298).

In drafting the code, the working group carried out extensive investigation and research, earnestly summarized experience gained in engineering practice, made reference to relevant advanced standards from abroad, and prepared the final text on the basis of a wide consultation of opinions.

The main technical contents of this code are: basic requirements; engineering geological investigation in the planning stage; engineering geological investigation in the prefeasibility study stage; engineering geological investigation in the feasibility study stage; engineering geological investigation in the tender design stage; and engineering geological investigation in the detailed design stage.

This code is administered by the National Energy Administration. It was proposed by, and is under the day-to-day administration of, the China Renewable Energy Engineering Institute (General Institute of Hydropower and Water Resources Planning and Design), which is also responsible for the interpretation of its specific technical contents.

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

Chief drafting organization: PowerChina Huadong Engineering Corporation Limited.

Participating drafting organizations: Zhejiang Huadong Construction Engineering Co., Ltd.; Huadong Engineering (Fujian) Corporation Limited.

Chief drafters: Shan Yegang, Jin Zhongliang, Wang Mingyuan, Yi Shenzhou, Li Sunquan, Zhou Chunhong, Lu Fei, Ye Zhiping, Chen Guohai, Zhou Huixin, Lin Jian, Rao Meng, Xu Xueyong, Sun Senjun, Chen Changhe.

Chief reviewers: Yang Jian, Zhu Jianye, Yang Jianhong, Chen Weidong, Wu Yongfeng, Wang Huiming, Xu Mo, Wang Jinguo, Jia Yonggang, Hu Guanghai, Lu Xiaoming, Hu Jisong, Zhong Jianping, Zhang Guofu, Wang Yaqun, Liu Zengjie, Ao Renjun, Zhao Tie, Wang Huiming, Li Wengang, Li Shisheng.

Publication data

NB/T 10388-2020, Code for Engineering Geological Investigation of Tidal Power Projects, is an energy industry standard of the People's Republic of China issued by the National Energy Administration. The cover carries the classification ICS 27.140 and the Chinese standard classification code P 61, the group used for hydropower and water resources engineering surveying and investigation.

The standard was released on 23 October 2020 and entered into force on 1 February 2021. The title page repeats the implementation date in full as 1 February 2021 and gives Beijing 2021 as the place and year of publication.

The organization in charge of drafting (chief editing department) is the China Renewable Energy Engineering Institute, the General Institute of Hydropower and Water Resources Planning and Design. The approving authority is the National Energy Administration.

The standard was promulgated by Announcement No. 5 of 2020 of the National Energy Administration, dated 23 October 2020. That announcement approved 502 energy industry standards listed in Annex 1, together with the English versions of 35 energy industry standards listed in Annex 2.

In the catalogue of industry standards attached to the announcement, NB/T 10388-2020 appears as item 4, under the Chinese title of the code, with approval date 2020-10-23 and implementation date 2021-02-01. The columns for the superseded standard and for the adopted international standard are both blank, which means the code is a new document and does not replace any earlier standard.

The code is published in Chinese, with an official English title printed on the cover and an official English table of contents printed after the Chinese one. No English version of the full text is announced in Annex 2 for this number.

Structure of the document

The code is organized in eight clauses followed by eight appendices and the customary closing matter. Clauses 1 to 3 set the purpose, the vocabulary and the requirements common to all stages; clauses 4 to 8 follow the design sequence of a tidal power project, one clause for each investigation stage.

Clause 4, Engineering Geological Investigation in Planning Stage, is divided into General Requirements, Regional Geology and Seismicity, Station Site, Natural Construction Materials and Investigation Report, and runs from page 5 to page 8 of the printed text.

Clause 5, Engineering Geological Investigation in Prefeasibility Study Stage, is divided into General Requirements, Regional Tectonic Stability and Seismic Effect, Reservoir, Tidal Barrage, Powerhouse Site, Sluice and Shiplock, Natural Construction Materials and Investigation Report, and runs from page 8 to page 16.

Clause 6, Engineering Geological Investigation in Feasibility Study Stage, is the longest of the code. It runs from page 16 to page 27 and adds to the previous subdivisions those devoted to Seismic Effect on Site and Foundation, Powerhouse, Substation and Cofferdam.

Clause 7, Engineering Geological Investigation in Tender Design Stage, covers General Requirements, Engineering Geology Review and Special Engineering Geological Investigation, Auxiliary and Temporary Structures, Natural Construction Materials and Investigation Report, on pages 27 and 28.

Clause 8, Engineering Geological Investigation in Detailed Design Stage, covers General Requirements, Special Engineering Geological Investigation, Geological Work in Construction Period and Data Processing, on pages 29 and 30.

The appendices provide the working tools referred to in the clauses: Appendix A, Applicability of Marine Geophysical Exploration Methods; Appendix B, Soil Classification; Appendix C, Drawings and Attachments of Engineering Geological Investigation Report; Appendix D, Seismic Classification of Construction Site; Appendix E, Criteria for Evaluating Soft Soil Subsidence; Appendix F, Classification of Submarine Shallow Gas; Appendix G, Water and Soil Corrosivity Evaluation; and Appendix H, Investigation and Suitability Evaluation of Hydraulic Fill Materials.

The closing matter comprises the Explanation of Wording in This Code on page 42, the List of Quoted Standards on page 43, and the Addition: Explanation of Provisions, the commentary on the clauses, which begins on page 44.

1 Scope

NB/T 10388-2020 governs the engineering geological investigation of tidal power projects in China. A tidal power scheme closes an estuary or a bay with a barrage carrying turbines and sluices, so the ground it is founded on is not ordinary ground: it is soft marine and estuarine sediment, often deep, sometimes with buried channels, subject to twice-daily loading and unloading by the tide, to scour where the flow is concentrated through the openings, and to seawater attack on concrete and steel. The code sets the general provisions and the defined terms, then the scope and depth of investigation at each design stage from planning through feasibility to detailed design and construction. It covers the regional geological and seismic setting, the marine geophysical survey and the drilling and sampling offshore and in the intertidal zone, the in-situ and laboratory testing of soft marine soils, and the hydrogeological and water chemistry work. It then sets out the assessment for each structure of the scheme: the powerhouse and its turbine passages, the tidal barrage and dykes, the sluices, the ship lock where there is one, the reservoir basin and its rim, and the borrow areas for fill. Foundation bearing capacity and settlement, slope and dyke stability, liquefaction, scour and siltation, and corrosion of buried works each receive their treatment, with the investigation report and drawings closing the code.

1.0.1 This code is formulated in order to unify the work tasks, the contents and the technical requirements of the several investigation stages of tidal power projects, and to ensure the quality of the investigation work and the quality of its deliverables.

1.0.2 This code applies to the engineering geological investigation of tidal power projects.

1.0.3 The engineering geological investigation of tidal power projects shall comply not only with this code but also with the provisions of the relevant current national standards.

2 Terms

Clause 2 defines eight terms, each given in Chinese with its official English equivalent and a full definition. The terms cover the object of the code, the seismic phenomena that govern the design of tidal works, and the marine features that the investigation has to identify.

2.0.1 Tidal power generation. Power generation that uses the head formed between the water level inside a reservoir and the tidal level of the open sea during flood and ebb tides, the reservoir being formed by building a barrage, a powerhouse and a sluice at the entrance of a bay or at a tidal estuary so as to separate the impounded water from the open sea.

2.0.2 Tidal power project. The collective designation of all the projects carried out in the course of building a tidal power station, including investigation, design, construction, and equipment manufacture and installation.

2.0.3 Seismic effect. The effects produced by seismic activity, including submarine landslides, submarine collapses, turbidity current subsidence, liquefaction of sandy soil and subsidence of soft soil.

2.0.4 Soft soil subsidence. The permanent deformation produced in soft and weak soils under the action of seismic loads.

2.0.5 Waters stratigraphic profiling. A method of investigating the structure of the submarine strata that makes use of the propagation characteristics of elastic waves in water and in underwater sediments.

2.0.6 Submarine mobile dune and sand wave. A submarine dune or sand wave that is in a state of continuous movement under the action of ocean waves, tides and sea currents.

2.0.7 Submarine shallow gas. Methane, carbon dioxide, hydrogen sulphide, ethane and similar gases accumulated in the shallow sediments of the sea bed.

2.0.8 Submarine obstacle. A submarine object, of natural or of human origin, that has an adverse influence on the construction of the project.

3 Basic requirements

3.0.1 The engineering geological investigation of a tidal power project should be divided into five stages: planning, prefeasibility study, feasibility study, tender design and detailed construction drawing design. For projects with simple geological conditions the investigation stages may be merged as appropriate.

3.0.2 The engineering geological investigation work of each stage shall be determined according to the requirements of the investigation contract or of the investigation task statement. The task statement shall specify the investigation stage, the characteristic indices of the project, the design intent and the requirements for the investigation work, and shall be accompanied by a general layout drawing of the project complex.

3.0.3 Before starting field work the investigation organization shall collect and analyse the existing geological, meteorological, hydrological, traffic and submarine obstacle data of the project area, carry out a site reconnaissance, become acquainted with the natural and working conditions, and prepare an engineering geological investigation outline on the basis of the design scheme and the requirements of the task. The outline may be adjusted as appropriate during its execution according to the changes in the actual situation.

3.0.4 The engineering geological investigation outline shall mainly include the following contents:

3.0.4-1 The origin of the task, the investigation stage, and the purpose and tasks of the investigation.

3.0.4-2 A general description of the project and of the topographical and geological conditions and working conditions of the sea area and estuary of the project site.

3.0.4-3 The existing geological, meteorological and hydrological data, the data on submarine obstacles and deep sea trenches, the main conclusions of the engineering geological investigation of the preceding stage, and the main opinions of its review and appraisal.

3.0.4-4 The technical standards on which the investigation work is based.

3.0.4-5 The investigation contents, the working approach, the technical requirements, the working methods and the layout of the exploration work.

3.0.4-6 The planned volume of work and the schedule.

3.0.4-7 The project management and the safety, quality and environmental protection assurance measures.

3.0.4-8 The contents and the quantity of the deliverables to be submitted.

3.0.5 The engineering geological investigation shall make comprehensive use of the various means of investigation and of advanced techniques, and shall lay out the engineering geological investigation work rationally, according to the type and the scale of the structures of the tidal power project, the degree of complexity of the topographical and geological conditions of the bay and the estuary, and the investigation tasks and depth requirements of each stage.

3.0.6 The scale of the engineering geological mapping of each stage shall be selected according to the investigation stage, the characteristics of the project and the topographical and geological conditions of the project area. The other exploration work shall be laid out on the basis of the results of the engineering geological mapping. Engineering geological mapping in the sea area should be carried out in combination with topographic surveying and geophysical exploration; engineering geological mapping on land shall comply with the relevant provisions of the current industry standard Code for Geological Mapping of Hydropower Projects NB/T 10074.

3.0.7 The exploration methods shall be selected according to the topographical and geological conditions, the characteristics of the structures of the tidal power project, the purpose of the investigation, and the differences between the land area and the sea area.

3.0.8 The geophysical exploration methods shall be selected according to the topographical and geological conditions of the project area, the characteristics of the rock and soil masses, and the characteristics of the tidal power project. The applicability of marine geophysical exploration methods should be selected according to the provisions of Appendix A of this code.

3.0.9 The items, the number and the methods of the physical and mechanical tests on rock and soil and of the in situ tests shall be determined in the light of the geological conditions, the investigation stage, the suitability of the test methods and the characteristics of the tidal power project. The samples and the in situ test points shall be selected so as to be representative, and a geological description of the samples shall be made. The classification of soils shall comply with Appendix B of this code. The physical and mechanical tests on rock and soil masses, the in situ tests in boreholes, the hydrogeological tests and the selection of parameter values shall comply with the following provisions:

3.0.9-1 The physical and mechanical tests on soils shall comply with the relevant provisions of the current national standard Standard for Geotechnical Testing Method GB/T 50123.

3.0.9-2 The tests on the physical and mechanical properties of rock shall comply with the relevant provisions of the current national standard Standard for Test Methods of Engineering Rock Mass GB/T 50266.

3.0.9-3 The in situ tests in boreholes shall comply with the relevant provisions of the current industry standard Code for In Situ Soil Tests in Boreholes of Hydropower Projects NB/T 35102.

3.0.9-4 The hydrogeological tests shall comply with the relevant provisions of the current industry standards Code for Water Pressure Tests in Boreholes of Hydropower Projects NB/T 35113 and Code for Pumping Tests in Boreholes of Hydropower Projects NB/T 35103.

3.0.9-5 The selection of the values of the physical and mechanical parameters of rock and soil masses should comply with the relevant provisions of the current national standard Code for Engineering Geological Investigation of Hydropower Projects GB 50287.

3.0.10 For unstable coastal slopes that require in situ monitoring and long term observation, the monitoring and observation schemes shall be designed according to the natural conditions, the characteristics of the tidal power project, the purpose of the observation and the investigation stage.

3.0.11 Where the engineering geological conditions of the site are complex and there exist major engineering geological problems affecting the benefits of the project and the safety of the structures, such as submarine landslides, submarine mobile dunes and sand waves, submarine shallow gas, active faults or submarine obstacles, a special engineering geological investigation shall be carried out or a dedicated study shall be undertaken.

3.0.12 During the investigation work, importance shall be attached to the collection of the various basic geological data; all data shall be true, accurate and complete, and shall be collated, analysed and filed in good time. The analysis and evaluation of the main engineering geological problems of the sea area shall be strengthened in the light of the type and characteristics of the structures of the tidal power project. During the construction period the earlier data shall be verified against the geological conditions exposed in the course of the works, and supplementary engineering geological investigation work shall be carried out as required.

3.0.13 A special exploration scheme shall be prepared before the engineering geological exploration is implemented, and the requirements of safe production and of environmental protection shall be satisfied during its implementation.

3.0.14 An engineering geological investigation report shall be prepared and submitted in every stage. The engineering geological investigation report shall comprise the main text, the drawings and the attachments. The drawings and the attachments of the engineering geological investigation report shall comply with Appendix C of this code.

4 Engineering geological investigation in the planning stage

4.1.1 The engineering geological investigation of the planning stage shall ascertain and analyse the basic geological conditions of the area being planned, and shall provide the engineering geological data needed for the planning of tidal power development and for the selection of the projects to be developed in the near term.

4.1.2 The tasks of the engineering geological investigation of the planning stage shall include the following contents:

4.1.2-1 To ascertain the general regional geology and seismicity of the planned station sites.

4.1.2-2 To ascertain the engineering geological conditions and the main engineering geological problems of the reservoir of each planned station site, and to analyse the conditions for forming the reservoir.

4.1.2-3 To ascertain the engineering geological conditions and the main engineering geological problems of the barrage of each planned station site, and to analyse the conditions for building the barrage.

4.1.2-4 To ascertain the occurrence of natural construction materials in the vicinity of the planned station sites.

4.2.1 The investigation of the regional geology and seismicity of a planned station site shall include the following contents:

4.2.1-1 The forms, types and distribution of the regional landforms.

4.2.1-2 The distribution, age and lithofacies characteristics of the strata within the region, and the genetic types and constituent materials of the Quaternary sediments.

4.2.1-3 The main structural units within the region, the types, attitude, scale and history of tectonic activity of the folds and faults, the historical earthquakes and the ground motion parameters of the site.

4.2.1-4 The regional hydrogeological characteristics.

4.2.2 The regional geological investigation shall collect and analyse the existing regional geological and seismological data and shall produce a regional geological map of the station site. On the basis of the analysis of the regional geological and seismological data of the neighbouring areas and of the current national standard Seismic Ground Motion Parameter Zonation Map of China GB 18306, preliminary ground motion parameters may be proposed for each station site.

4.2.3 The preliminary evaluation of the regional tectonic stability of a station site shall be made on the basis of the analysis of the regional geology, the seismicity, the neotectonic movement and the activity of the regional faults.

4.2.4 The scale of the regional geological map of a station site should be selected from 1:500 000 to 1:100 000, and the extent of the regional geological map shall satisfy the requirements of the planning scheme.

4.3.1 The investigation of the reservoir of each planned station site shall include the following contents:

4.3.1-1 To ascertain the landforms and their changes, such as the types and forms of the coastal zone and of the estuarine banks of the reservoir area.

4.3.1-2 To ascertain the engineering geological and hydrogeological conditions of the reservoir area.

4.3.1-3 To ascertain the distribution and the characteristics of landslides, encircling embankments, revetments and similar features having a major influence on the reservoir.

4.3.1-4 To ascertain the groundwater level and the distribution of the aquifers and aquicludes of the enclosing dykes of the reservoir area and of the narrow and thin watersheds of the bay, and to analyse preliminarily the possibility of reservoir leakage.

4.3.2 The investigation of the reservoir may be carried out in combination with the regional geological survey work. Where engineering geological problems that may have a major influence on the reservoir exist on land, engineering geological mapping of the reservoir area shall be carried out and exploration work shall be laid out as required. The scale of the engineering geological mapping should be selected from 1:50 000 to 1:10 000, and its extent shall satisfy the needs of the engineering geological evaluation.

4.3.3 The investigation of each planned barrage site shall include the following contents:

4.3.3-1 To ascertain the landform features and types of the sea bed and of the coastal zone of the barrage site.

4.3.3-2 To ascertain the strata and lithology of the barrage site, the distribution and genetic types of the Quaternary sediments, and the thickness, sequence and constituent materials of the sea bed cover layer.

4.3.3-3 To ascertain the types, scale and character of the geological structures of the barrage site, with emphasis on the active faults.

4.3.3-4 To ascertain the physico-geological phenomena of the rock mass of the barrage site, such as weathering, unloading, landsliding and collapse, and the stability of the banks; and to ascertain the distribution and the characteristics of submarine landslides, submarine shallow gas, submarine mobile dunes and sand waves, and submarine obstacles.

4.3.3-5 To ascertain the permeability of the rock and soil masses of the barrage site, the groundwater level and the hydrochemical characteristics.

4.3.4 The investigation methods for the barrage site shall comply with the following provisions:

4.3.4-1 The scale of the engineering geological mapping should be selected from 1:10 000 to 1:5 000, and the extent of the mapping shall include the barrage sites being compared and the banks near the barrage. Where the barrage sites being compared are far apart, engineering geological mapping may be carried out for each of them separately.

4.3.4-2 Among the exploration methods, geophysical exploration should be the main one and drilling should be auxiliary.

4.3.5 The layout of the exploration of a barrage site shall comply with the following provisions:

4.3.5-1 Not less than one exploration section shall be laid out along the axis of each planned barrage site; geophysical exploration shall be laid out along the exploration section and boreholes should be laid out, with a borehole spacing of 500 m to 1 500 m; for the barrage site of a project to be developed in the near term there shall be not less than three boreholes.

4.3.5-2 The depth of the boreholes in the sea area should be three to five times the height of the barrage. Where bedrock is encountered within the expected borehole depth, the depth may be reduced, and it should be controlled so as to penetrate not less than 10 m into the weakly weathered zone.

4.3.5-3 The main rock and soil layers shall be sampled for physical and mechanical tests, and the surface water and the groundwater shall be sampled for simplified water quality analysis. Field tests may be carried out as required.

4.4.1 A general survey shall be made of the natural construction materials within a radius of 40 km of each planned station site. The types, distribution, surrounding environmental conditions and quality of the available natural construction materials shall be ascertained and their reserves shall be estimated. A distribution map of the borrow areas should be prepared at a scale of 1:100 000 to 1:50 000.

4.4.2 For the natural construction materials of station sites to be developed in the near term, a small amount of exploration and sampling tests should be laid out in order to ascertain the quality and the reserves of the borrow areas and the conditions of exploitation and transport.

4.4.3 For purchased stone and sand and gravel materials, the lithology of the source area, the quality, the reserves and the quantity available for supply shall be ascertained.

4.4.4 The exploration, the sampling tests, the data processing and the quality evaluation of natural construction materials may be carried out according to the relevant provisions of the current industry standard Code for Investigation of Natural Construction Materials of Hydropower Projects NB/T 10235.

4.5.1 The main text of the engineering geological investigation report of the planning stage shall include a general description, the regional geology and seismicity, the engineering geological conditions of each planned station site, the comparison of the station sites, and the conclusions and recommendations.

4.5.2 The general description shall include the general features of the planned station sites, the degree of previous geological study and the volume of work completed in the present investigation stage.

4.5.3 The regional geology and seismicity shall include the landforms of the sea area and the estuary, the regional geological and regional hydrogeological conditions, the regional tectonic framework and the seismic activity, the ground motion parameters, and the preliminary evaluation of the regional tectonic stability.

4.5.4 The engineering geological conditions of each planned station site may be written in sections according to the layout of the structures, namely reservoir, barrage and natural construction materials, and shall include the following contents:

4.5.4-1 The engineering geological conditions of the reservoir, mainly including the basic geological conditions of the reservoir area and the preliminary evaluation of engineering geological problems such as reservoir leakage and the stability of the reservoir banks.

4.5.4-2 The engineering geological conditions of the barrage, mainly including the engineering geological conditions of the sea area and of the land area. The engineering geological conditions of the sea area mainly include the submarine landforms, the distribution and characteristics of the rock and soil layers, the hydrogeological conditions, and the distribution and characteristics of submarine landslides, submarine shallow gas, submarine mobile dunes and sand waves and submarine obstacles; the engineering geological conditions of the land area mainly include the landforms, the strata and lithology, the geological structures, the physico-geological phenomena and the hydrogeological conditions. The preliminary evaluation of the engineering geological conditions of each barrage site shall also be given.

4.5.4-3 A general description of the natural construction materials.

4.5.5 The comparison of station sites shall put forward an engineering geological comparison opinion on the basis of the discussion of the engineering geological conditions of each planned station site.

4.5.6 The conclusions and recommendations shall mainly include the engineering geological analysis and argumentation opinions on the planned station sites and on the station sites to be developed in the near term, and shall put forward recommendations for the engineering geological investigation work of the next stage.

5 Engineering geological investigation in the prefeasibility study stage

5.1.1 The engineering geological investigation of the prefeasibility study stage shall, on the basis of the investigation of the planned station sites, make a preliminary selection of the representative barrage site, make a preliminary engineering geological evaluation of the representative barrage site and of the layout scheme of the project complex, and provide the engineering geological data needed for the argumentation of the layout scheme of the project complex.

5.1.2 The investigation tasks of the prefeasibility study stage shall include the following contents:

5.1.2-1 To study the regional tectonic stability, to evaluate the tectonic stability of the project site, and to make a preliminary evaluation of the seismic effect at the site.

5.1.2-2 To ascertain preliminarily the main engineering geological conditions of the reservoir area and to evaluate preliminarily the main engineering geological problems having a major influence on the scheme.

5.1.2-3 To ascertain preliminarily the engineering geological conditions of the sites of the structures, such as the barrage, the powerhouse site, the sluice and the shiplock, as well as the distribution and characteristics of unfavourable geological phenomena and submarine obstacles such as submarine landslides, submarine shallow gas and submarine mobile dunes and sand waves; and to evaluate preliminarily the major engineering geological problems affecting the viability of the scheme and the engineering geological conditions of the representative barrage and of the layout scheme of the project complex.

5.1.2-4 To evaluate preliminarily the corrosivity of sea water, groundwater and soil towards concrete structures and steel structures.

5.1.2-5 To make a preliminary survey of the main natural construction materials required by the representative barrage type.

5.2.1 The study of the regional tectonic stability and the evaluation of the seismic effect shall include the following contents:

5.2.1-1 The study of the regional tectonic setting.

5.2.1-2 The determination of the ground motion parameters.

5.2.1-3 The evaluation of the seismic effect on the site and on the foundation.

5.2.2 The study of the regional tectonic setting shall comply with the following provisions:

5.2.2-1 Data shall be collected on the strata and lithology, the regional active faults, the modern tectonic stress field, the seismic activity and the seismic zoning within a radius of not less than 150 km around the barrage site.

5.2.2-2 The regional faults and their activity within 25 km of the area near the barrage site shall be studied.

5.2.2-3 Where the barrage and the structures of the project complex are close to an active fault, the influence of the active fault on the barrage site shall be studied. The identification of active faults on land shall comply with the relevant provisions of the current national standard Code for Engineering Geological Investigation of Hydropower Projects GB 50287; active faults in the sea area shall be identified comprehensively on the basis of the submarine landforms, the seismic activity, the dislocation of strata and the geophysical characteristics.