NB/T 11669-2024Technical code for underwater repair of hydraulic structures (English PDF)

Foreword

This document was issued on 24 September 2024 by the National Energy Administration of the PRC and takes effect on 24 March 2025.

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 59.

This code has been prepared by the drafting group in accordance with the requirements of the Notice of the General Department of the National Energy Administration on Issuing the 2021 Plan for the Development and Revision of Industry Standards in the Energy Field and the Plan for Translation of Foreign Language Editions (Guo Neng Zong Tong Ke Ji [2021] No. 92), on the basis of extensive investigation and research, a careful summing-up of practical experience and the wide solicitation of opinions.

The main technical contents of this code are: general provisions; terms; basic requirements; detection and evaluation; underwater repair materials; treatment for underwater concrete cracks; repair of underwater concrete structures; treatment for defects at underwater concrete surfaces; treatment for underwater cavities and holes; repair of underwater metal structures; and occupational health and safety and environmental protection.

This code is administered by the National Energy Administration. It was proposed by, and is under the routine administration of, the China Renewable Energy Engineering Institute. The Sub-technical Committee on Construction Design of the Standardization Technical Committee on Hydropower Investigation and Design of the Energy Industry (NEA/TC15/SC3) is responsible for the interpretation of the specific technical contents.

Comments or suggestions arising during the implementation of this code should be addressed to the China Renewable Energy Engineering Institute, at No. Jia 57 and No. Yi 57 Andingmenwai Street, Dongcheng District, Beijing, postcode 100011.

Chief editing organizations of this code: China Renewable Energy Engineering Institute; PowerChina Guiyang Engineering Corporation Limited; China Gezhouba Group Company Limited; Qingdao Pacific Underwater Science and Technology Engineering Company Limited; and China Institute of Water Resources and Hydropower Research.

Participating organizations of this code, first group: Tsinghua University; China Gezhouba Group No. 2 Engineering Company Limited; Beijing IWHR Haili Engineering Technology Company Limited; China Gezhouba Group Survey and Design Company Limited; and China Gezhouba Group Machinery and Ship Company Limited.

Participating organizations of this code, second group: Nanjing Hydraulic Research Institute, jointly under the Ministry of Water Resources, the Ministry of Transport and the National Energy Administration; PowerChina Beijing Engineering Corporation Limited; Hangzhou Meibu Material Technology Company Limited; Guangzhou Jiangda Diving and Dredging Engineering Company Limited; CHN Energy Dadu River Jinchuan Hydropower Construction Company Limited; and Sinohydro Bureau 9 Company Limited.

Forty-eight chief drafters are named in the Chinese foreword of this code; the list is printed in Chinese characters only and is reproduced there in full.

Fifteen chief reviewers are named in the Chinese foreword of this code; that list too is printed in Chinese characters only.

Publication Announcement

Announcement No. 3 of 2024 of the National Energy Administration. In accordance with the Standardization Law of the People's Republic of China and the Administrative Measures for Energy Standardization, the National Energy Administration approved and issued 384 energy industry standards headed by Design Code for Rockfill Concrete Dams (Annex 1), 32 foreign language editions of energy industry standards headed by Operation code for liquefied natural gas receiving terminal (Annex 2), and 2 amendment notices for energy industry standards headed by Code for Monitoring of Rock and Soil Masses in Hydropower Projects (Annex 3).

The announcement carries three annexes: Annex 1, Catalogue of Industry Standards; Annex 2, Catalogue of Foreign Language Editions of Industry Standards; and Annex 3, Amendment Notices for Industry Standards. It was issued by the National Energy Administration on 24 September 2024.

In the Catalogue of Industry Standards this code appears as serial number 74: standard number NB/T 11669-2024, standard title Technical Code for Underwater Repair of Hydraulic Structures, approval date 2024-09-24, implementation date 2025-03-24. The columns for the superseded standard and for the adopted international standard are blank, so this code supersedes no earlier standard and adopts no international standard.

Chief editing department: China Renewable Energy Engineering Institute. Approving department: National Energy Administration. Date of implementation: 24 March 2025. The code is classified under ICS 27.140 and Chinese Standard Classification Code P 59, professional class P, and was published by China Water and Power Press, Beijing, in 2025.

Structure of the Code

Chapter 4, Detection and Evaluation, runs from page 5 to page 8 and is divided into general requirements, conventional detection, special detection, and analysis and evaluation.

Chapter 5, Underwater Repair Materials, runs from page 9 to page 24 and is the longest chapter of the code. Besides its general requirements it covers underwater non-dispersible concrete, underwater non-dispersible mortar, underwater epoxy mortar or underwater epoxy concrete, underwater epoxy resin or underwater polyurethane grouting materials, underwater epoxy or underwater polyester resin coating, geomembrane, rubber protective sheet, high plastic filler, flexible carbon fiber composite plate, underwater sealing agent, and underwater adhesive and underwater anchorage adhesive.

Chapter 6, Treatment for Underwater Concrete Cracks, runs from page 25 to page 37 and is divided into general requirements, technical requirements, repairing construction, and quality inspection.

Chapter 7, Repair of Underwater Concrete Structures, runs from page 38 to page 46 and follows the same four-part arrangement of general requirements, technical requirements, repairing construction, and quality inspection.

Chapter 8, Treatment for Defects at Underwater Concrete Surface, runs from page 47 to page 50 and is likewise divided into general requirements, technical requirements, repairing construction, and quality inspection.

Chapter 9, Treatment for Underwater Cavities and Holes, runs from page 51 to page 60 and is divided into general requirements, technical requirements, repairing construction, and quality inspection.

Chapter 10, Repair of Underwater Metal Structures, runs from page 61 to page 66 and is divided into general requirements, technical requirements, repairing construction, and quality inspection.

Chapter 11, Occupational Health and Safety and Environmental Protection, begins at page 67. It is followed by four appendices, by the Explanation of Wording in This Code at page 76, by the List of Quoted Standards at page 77, and by the Addition: Explanation of Provisions at page 81.

1 Scope

NB/T 11669-2024 is the Chinese technical code for repairing hydraulic structures underwater - work carried out without drawing down the reservoir or dewatering the structure, because on an operating hydropower scheme emptying is often impossible or would cost more than the repair. It applies to dams, spillways and stilling basins, intakes and outlets, gates and their embedded parts, piers, aprons and slope protection. The code sets the general provisions and the defined terms, then the basic requirements: the underwater investigation and damage survey that must precede any repair, the diving and remotely operated vehicle work involved, the assessment of the damage and the choice of repair method against the depth, the flow velocity and the condition of the substrate. It then covers the methods in turn - underwater concreting by tremie and by pumped placement, grout-injected aggregate, underwater-curing epoxy and polymer mortars and grouts, crack injection, surface coatings and linings applied underwater, patch repair of erosion and cavitation damage, anchoring and reinforcement, and the placement of fabric formwork and precast elements. For each it gives the materials and their qualification, the surface preparation, the placing procedure and the quality control applied in conditions where the work cannot be seen directly. Inspection and acceptance of the completed repair, the safety of the diving operations, and the monitoring expected afterwards close the document. It applies to hydropower and water resources structures in China.

1.0.1 This code is formulated in order to standardize the design and construction of underwater repair of hydraulic structures and to guarantee the quality and the effectiveness of the repair.

1.0.2 This code is applicable to the underwater repair of hydraulic structures.

1.0.3 The underwater repair of hydraulic structures shall follow the principles of being safe and reliable, technically advanced, ecologically and environmentally sound, and economically applicable, and new technologies, new processes, new materials and new methods shall be actively adopted.

1.0.4 In addition to the requirements of this code, the underwater repair of hydraulic structures shall also comply with the provisions of the relevant current national standards.

2 Terms

2.0.1 underwater repair

The repair treatment of defects of a building or structure, carried out in a water environment, where the part to be repaired lies below the water surface.

2.0.2 non-dispersible underwater mortar

Cement mortar which, after the addition of an anti-washout flocculating admixture, possesses non-dispersibility under water.

2.0.3 self-protected underwater concrete (SPUC)

A self-compacting concrete placed under water by means of the self-protection technique.

2.0.4 underwater to in-air strength ratio

The ratio of the compressive strength of the tested concrete formed in water to the compressive strength of the tested concrete formed in air, expressed as a percentage.

2.0.5 wet underwater welding

A method in which, in a water environment, an electric arc is used as the heat source to carry out fusion welding directly on underwater components.

2.0.6 dry underwater welding

A method in which the welding operation is carried out under water and the water around the area to be welded is displaced by external intervention measures before welding is performed.

2.0.7 structural defect

A structural loss or damage that affects the safe operation of a hydraulic structure.

2.0.8 surface damage

A defect affecting the safe operation of a hydraulic structure that lies within the thickness of the concrete cover, or, in the case of plain concrete, whose damage depth is not greater than 5 cm.

2.0.9 grouting body

The solid object that receives the grout.

3 Basic Requirements

3.0.1 According to the type of defect or deterioration, the underwater repair of hydraulic structures may be divided into treatment for underwater concrete cracks, repair of underwater concrete structures, treatment for defects at underwater concrete surfaces, treatment for underwater cavities and holes, and repair of underwater metal structures. Underwater repair shall not affect the design and service functions of the structure and shall not impair the operational safety of the structure.

3.0.2 The underwater repair scheme shall be determined after a comprehensive evaluation based on the operating condition of the structure, on the safety monitoring results and on the underwater detection results. The underwater repair scheme shall include the project overview, the repair scope, the design scheme, the construction conditions, the construction methods, the quality requirements, the allocation of resources, the safety and environmental protection measures, the emergency plan and other relevant items.

3.0.3 For underwater repair, a special construction scheme for hazardous and large-scale works and an emergency plan for underwater operations shall be prepared as prescribed.

3.0.4 The selection of the underwater repair materials and the underwater repair scheme shall satisfy the requirements of environmental protection and of water and soil conservation.

3.0.5 The following data shall be collected for underwater repair:

3.0.5 (1) The design data of the hydraulic structure.

3.0.5 (2) The operating condition of the hydraulic structure together with the safety monitoring results and the underwater detection results.

3.0.5 (3) The inspection reports, the certificates of conformity and the instruction manuals of the underwater repair materials.

3.0.5 (4) The conditions of the water body surrounding the hydraulic structure, including water depth, flow velocity, water temperature, water quality, silt deposition, visibility and the like.

3.0.5 (5) Other data related to the underwater repair.

3.0.6 The following work shall be completed before underwater repair construction begins:

3.0.6 (1) The surveying, probing, inspection and testing required for the underwater repair construction.

3.0.6 (2) The preparation and the approval or expert demonstration of the documents of the special construction scheme for the underwater repair.

3.0.6 (3) The various temporary construction facilities required for the construction.

3.0.6 (4) The technical and safety disclosure for the underwater repair.

3.0.6 (5) The on-site productive tests required by the design.

3.0.6 (6) Other work related to the on-site construction.

3.0.7 Underwater cleaning should be carried out before the repair of an underwater concrete structure. The cleaning shall not cause secondary damage to the concrete surface or damage to the structure. After cleaning, the concrete base surface shall be clean and free from loose material, from aquatic growth and from other attachments.

3.0.8 The diving working environment for underwater repair should comply with the following provisions:

3.0.8 (1) The visibility at the underwater working site should not be less than 1 m.

3.0.8 (2) The water temperature should be from 5 degrees Celsius to 30 degrees Celsius, and the flow velocity of the water should not be greater than 0.5 m/s.

3.0.9 The measuring instruments required for the repair construction and for the tests and detection shall be verified or calibrated as required.

3.0.10 Where new technologies, new processes, new materials or new methods are used for underwater repair, the necessary testing and verification work shall be carried out.

3.0.11 The underwater repair construction shall comply with the relevant provisions of the current industry standards Code of General Safety Technique for Construction of Hydropower and Water Resources Projects DL/T 5370, Code of Safety Technique for Civil Construction of Hydropower and Water Resources Projects DL/T 5371, and Code of Environmental Protection Technique for Construction of Hydropower and Water Resources Projects DL/T 5260.

3.0.12 The underwater repair construction shall pay attention to the quality control of the construction process, with synchronous monitoring carried out above the water. After the construction is completed, quality inspection shall be carried out as required.

3.0.13 For the construction quality of underwater repair, the appropriate inspection timing and inspection locations shall be selected according to the quality inspection items. The inspection locations should be selected according to the following principles:

3.0.13 (1) Locations where an anomaly is identified by analysis of the construction records.

3.0.13 (2) Locations where the construction quality may have been affected by restrictive conditions or by unfavourable construction factors.

3.0.13 (3) Locations taken at random.

3.0.14 Records of the construction process and of the quality inspection shall be produced for underwater repair. On completion of the quality inspection an inspection report shall be prepared; the report should include an overview, the construction methods and the quality control criteria, the quality inspection methods and the test results, the problems found during the inspection, the conclusions, and annexed material such as drawings, tables and video records.

3.0.15 The construction quality shall be assessed comprehensively on the basis of the records of the construction process and of the results of the quality inspection.