NB/T 10222-2019Code for construction and acceptance of metro linkage tunnel of freezing method (English PDF)

Foreword

This document was issued on 4 June 2019 by the National Energy Administration of the PRC and takes effect on 1 October 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 93.060, Chinese classification P 00/09.

This code was prepared in accordance with the Notice of the General Department of the National Energy Administration on Issuing the 2017 Plan for the Formulation and Revision of Sector Standards in the Energy Field and the Plan for the Translation and Publication of English Versions (Guo Neng Zong Tong Ke Ji [2017] No. 52).

The chief editing organizations are China Coal No. 5 Construction Co., Ltd., Henan Guolong Mining Construction Co., Ltd. and China Coal Tunnel Engineering Co., Ltd., which drew up the code jointly with the participating organizations.

During the drafting work the editorial group carried out in-depth investigation and research, summarized the scientific and technological achievements and the construction technologies that recent practice has proved to be mature and effective, solicited the opinions of the organizations and experts concerned in a wide range of forms, and settled the final text after repeated discussion, study and revision and after formal examination.

The code is made up of 10 chapters and 8 appendices. Its main contents are general provisions, terms, basic requirements, construction preparation, freezing and related design, freezing construction, excavation and support, monitoring and control, safety and green construction, and engineering quality acceptance.

The National Energy Administration is responsible for the administration of this code; the China Coal Construction Association is responsible for its routine management and for the adjustment and revision of local contents; the chief editing organization China Coal No. 5 Construction Co., Ltd. is responsible for the interpretation of the individual provisions.

Users who have comments or suggestions during the application of this code are invited to send them to China Coal No. 5 Construction Co., Ltd., 241 Huaihai West Road, Xuzhou City, Jiangsu Province, postcode 221006, e-mail cc5c at cc5c.com, so that they may be taken into account in a future revision.

The participating organizations named in the foreword are Jiangsu Mining Engineering Group Co., Ltd., Henan Energy and Chemical Construction Group Co., Ltd., Yankuang Xinlu Construction and Development Co., Ltd., the Quality Supervision Centre Station for Coal Industry Construction Projects of Guizhou, the Quality Supervision Centre Station for Coal Industry Construction Projects of Henan, the Quality Supervision Station for Construction Projects of the Jincheng Mining Area, Shandong Runlu Building Material Testing Technology Service Co., Ltd., Guizhou Coal Mine Design and Research Institute Co., Ltd. and Lanzhou Coal Mine Design and Research Institute.

The foreword names 40 chief drafters, headed by Liu Wenbin, Liu Peinian, Dai Dongsheng, Li Xinzheng and Zhang Daohai, and 20 chief examiners, headed by Sun Shouren, Qi Jilong, Yue Fengtian, Hua Zhaowen and Zhao Xiong.

Publication data and approval record

NB/T 10222-2019 is an energy sector standard of the People's Republic of China, issued under the NB series by the National Energy Administration.

The cover carries the international classification ICS 93.060, the Chinese standard document classification code P 00/09 and the filing number J2717-2019.

The date of issue printed on the cover is 4 June 2019 and the date of implementation is 1 October 2019.

The title page states that the chief editing department is the China Coal Construction Association, that the approving department is the National Energy Administration and that the code takes effect on 1 October 2019.

The approval is recorded in Announcement No. 4 of 2019 of the National Energy Administration, dated 4 June 2019, by which 297 sector standards were approved: 105 energy standards (NB), 168 electric power standards (DL) and 24 petrochemical standards (NB/SH).

In the catalogue of sector standards annexed to that announcement this code appears as item 9, with the standard number NB/T 10222-2019, the publishing organization Emergency Management Press, the approval date 2019-06-04 and the implementation date 2019-10-01; the columns for the superseded standard and for the adopted standard number are both empty, so the code does not replace an earlier document.

The book was published by Emergency Management Press, 35 Shaoyaoju, Chaoyang District, Beijing, postcode 100029, website www.cciph.com.cn, printed by Beijing Yueshi Printing Co., Ltd. and distributed through the Xinhua Bookstores.

The printing record gives a trim size of 850 mm by 1168 mm, 1/32 format, 3 and 5/8 printed sheets and about 85 thousand characters, with the first edition and the first printing both dated March 2020, internal number 20193549 and a list price of 30.00 yuan.

The body of the code runs to page 62, the eight appendices occupy pages 67 to 74, the explanation of wording is on page 75, the list of reference standards on page 76, and the explanation of provisions begins on page 77.

Structure of the technical chapters

The technical requirements of the code are distributed over eight further chapters, whose headings and sub-headings are reproduced here from the official English table of contents printed in the book.

Chapter 3, Basic Requirements, begins on page 6 and is written as a single block of clauses without subdivisions.

Chapter 4, Construction Preparation, runs from page 7 and is divided into 4.1 General Provisions, 4.2 Basic Data Preparation and 4.3 On-site Preparation.

Chapter 5, Freezing and Related Design, is the longest design chapter and runs from page 10 to page 25. Its nine sections are 5.1 General Provisions, 5.2 Design of Freezing Wall, 5.3 Freezing Hole Design, 5.4 Initial Lining Design, 5.5 Pre-reinforced Bracket Design, 5.6 Protection Door Design, 5.7 Thermal Insulation Design, 5.8 Refrigeration Station Design and 5.9 Power Supply Design.

Chapter 6, Freezing Construction, runs from page 26 to page 35 and is divided into 6.1 General Provisions, 6.2 Freezing Hole Construction, 6.3 Freezing Pipe Installation, 6.4 Installation of Feeding Pipes, 6.5 Refrigeration Station Installation, 6.6 Refrigeration Station Operation, 6.7 Detection and Determination of Frozen Wall and 6.8 Freezing and Dismantling of Refrigeration Station.

Chapter 7, Excavation and Support, runs from page 36 to page 45 and is divided into 7.1 General Provisions, 7.2 Pre-reinforced Brackets and Protective Doors, 7.3 Excavation Preparation and Trial Excavation, 7.4 Excavation, 7.5 Initial Lining Construction, 7.6 Waterproof Construction, 7.7 Construction of Permanent Structures, 7.8 Filling and Sealing of Freezing Hole and 7.9 Filling and Melting Grouting.

Chapter 8, Monitoring and Control, runs from page 46 to page 49 and is divided into 8.1 General Provisions, 8.2 Monitoring Content and 8.3 Monitoring Requirements.

Chapter 9, Safety and Green Construction, runs from page 50 to page 51 and is divided into 9.1 Safety Construction and 9.2 Green Construction.

Chapter 10, Engineering Quality Acceptance, runs from page 52 to page 62 and is the acceptance part of the code.

The ten sections of Chapter 10 are 10.1 General Provisions, 10.2 Freezing Drilling Engineering, 10.3 Freezer Installation Project, 10.4 Installation Acceptance of Refrigeration Station, 10.5 Refrigeration Engineering, 10.6 Sealing and Melting Grouting Works, 10.7 Excavation Project, 10.8 Initial Lining Project, 10.9 Waterproof Layer Project and 10.10 Permanent Structural Engineering.

The sequence of the chapters follows the sequence of the works on site: preparation, design of the freezing works, execution of the freezing, excavation and support under the protection of the freezing wall, monitoring, safety, and finally acceptance of the finished work.

The acceptance chapter mirrors the construction chapters item by item, so that each of the main construction operations named in Chapters 6 and 7 has a corresponding acceptance section in Chapter 10.

The freezing design chapter covers not only the frozen ground itself but also the plant that produces the cold and the electricity that drives it, since sections 5.8 and 5.9 deal with the refrigeration station and with the power supply.

The terminology of Chapter 2 is used consistently throughout the technical chapters, in particular the terms freezing wall, freezing hole, refrigerator, brine system and refrigeration station.

Appendices and supplementary material

The code carries eight appendices, lettered A to H, which occupy pages 67 to 74 and consist of the standard record and acceptance forms to be used on site.

Appendix A, on page 67, is the Original Record Table for Drilling Construction.

Appendix B, on page 68, is the Borehole Freezing Pipe Pressure Original Record Table, used for the pressure testing of the freezing pipes in the boreholes.

Appendix C, on page 69, is the Refrigeration Station Operation Record Table.

Appendix D, on page 70, is the Procedure Quality Acceptance Record.

Appendix E, on page 71, is the Subitem Quality Acceptance Records.

Appendix F, on page 72, is the Division and Sub-Division Engineering Quality Acceptance Records.

Appendix G, on page 73, is the Subdivision Engineering Quality Control Data Verification Record.

Appendix H, on page 74, is the form for the Records of Apparent Quality Inspection of Connecting Passage Freezing Construction of Tunnel.

Page 75 carries the Explanation of Wording in This Standard, which sets out how the degrees of obligation expressed by the verbs used in the clauses are to be understood.

Page 76 carries the list of Reference Standards, that is the other national and sector standards referred to in the text.

The volume ends with the Addition: Explanation of Provision, beginning on page 77, which is the clause-by-clause commentary issued together with the code.

1 Scope

NB/T 10222-2019 governs the construction and acceptance of tunnel cross-passages built by the ground freezing method. When two parallel bored tunnels - a metro line, or a similar pair on another kind of project - must be connected by a short passage through saturated soft ground, the soil between them cannot be excavated as it stands: it would flow into the opening. Freezing it first turns the ground into a temporary wall of frozen soil strong and watertight enough to excavate inside. The code sets the general provisions and the defined terms, then the requirements on the investigation of the ground and groundwater, and on the design of the freezing scheme - the layout and depth of the freeze pipes, the thickness and temperature of the frozen wall, the brine or liquid nitrogen system, and the monitoring that proves the wall has closed. Construction follows in sequence: drilling and installing the freeze pipes from inside the tunnel, the refrigeration plant and its operation, the active freezing period, the excavation and temporary support once the frozen wall is confirmed, the permanent lining and waterproofing, and then the controlled thawing and the grouting that compensates for thaw settlement. Temperature, pressure, deformation and settlement monitoring run throughout. Quality control, the acceptance of each stage and the records required close the code. Note that the printed English title renders the Chinese cross-passage between tunnels as metro linkage tunnel, which is narrower than the original.

Chapter 1 sets out the purpose of the code, its field of application, the activities it governs, the technical policy it promotes and its relationship with other standards. It occupies page 1 of the body text and contains five clauses, numbered 1.0.1 to 1.0.5.

1.0.1 This code is formulated in order to strengthen the management of freezing construction of tunnel connecting passages, to unify the technical requirements for the freezing method of construction and the acceptance standard for works of tunnel connecting passages, and to ensure construction safety and engineering quality.

1.0.2 This code applies to tunnel connecting passage works built by the freezing method for urban metro systems and for other sectors.

1.0.3 The freezing design, the construction management, the engineering quality acceptance and the management of the engineering records of tunnel connecting passages shall comply with the provisions of this code.

1.0.4 In the freezing design and the construction of tunnel connecting passages, advanced and mature new technologies, new techniques, new equipment and new materials shall be promoted and applied.

1.0.5 In addition to complying with this code, the freezing method construction of tunnel connecting passage works shall also comply with the provisions of the relevant national and sector standards.

2 Terms

Chapter 2 defines the vocabulary of the code. It begins on page 2 and runs to page 6, and contains twenty-six entries numbered 2.0.1 to 2.0.26, each given with its Chinese term and its English equivalent.

2.0.1 Tunnel connect passage: a transverse passage arranged at a given spacing between two single-track tunnels, abbreviated to connecting passage. The connecting passage serves for emergency evacuation, for drainage and for fire protection. In this code the connecting passage is the collective name for the passage itself and for the pump station.

2.0.2 Freezing method construction: a special construction method in which, before the underground structure is built, refrigeration technology is used to freeze and reinforce the unstable strata surrounding the structure so as to form a freezing wall that carries load temporarily, cuts off water and satisfies the safety needs of the works, after which the excavation and lining of the structure are carried out under the protection of that freezing wall.

2.0.3 Clean water system: the cooling water circulation system formed by the condenser, the cooling tower, the clean water pump, the pipework, the valves and the associated components; its circulating medium is clean water and its function is to cool the refrigerating machine.

2.0.4 Brine system: the refrigerant circulation system formed by the evaporator, the brine tank, the refrigerators, the brine pump, the pipework, the valves and the associated components; its circulating medium is a calcium chloride brine solution and its function is to convey the cooling capacity.

2.0.5 Refrigeration system: the refrigerant circulation system formed by the refrigerating machine, its auxiliary equipment and the associated components.

2.0.6 Frozen soil column: the approximately cylindrical body of frozen soil formed when the refrigerator exchanges heat with the surrounding water-bearing stratum and freezes it.

2.0.7 Freezing wall: the body of frozen rock and soil of a given thickness, strength and depth formed by refrigeration technology in the strata around the structure, also called a frozen soil curtain or a frozen soil wall.

2.0.8 Freezing wall thickness: the minimum distance between any point on one face of the freezing wall and the other face. The design thickness of the freezing wall is the minimum thickness that the freezing wall outside the excavation face of the structure to be built is required to reach; the effective thickness of the freezing wall is the thickness actually reached by the freezing wall outside that excavation face.

2.0.9 Average temperature of freezing wall: the mean value of the temperature distribution within the frozen range of the design freezing wall.

2.0.10 Freezing wall closing time: the time required, from the beginning of freezing of the strata, for the frozen soil columns formed by all adjacent refrigerators on the main ring of refrigerators around the structure to intersect completely as required by the design.

2.0.11 Stage of formation of freezing wall: the time required, from the beginning of freezing of the strata, for the freezing wall to reach the design requirements, also called the formation period of the freezing wall.

2.0.12 Stage of maintaining of freezing wall: the period during which, after the freezing wall has reached the design requirements, cooling capacity continues to be delivered to the refrigerators in order to keep the freezing wall in conformity with the design requirements and so guarantee safety during the construction of the structure, also called the maintenance freezing period.

2.0.13 Freezing hole: a borehole arranged around the connecting passage as required by the design for the installation of a refrigerator; freezing holes are of two kinds, horizontal holes and inclined holes.

2.0.14 Main freezing hole: where holes are drilled from the tunnels on both sides of the connecting passage, the side with the larger number of freezing holes is called the main freezing hole side.

2.0.15 Deputy freezing hole: where holes are drilled from the tunnels on both sides of the connecting passage, the side with the smaller number of freezing holes is called the secondary freezing hole side.

2.0.16 Thru hole: a hole drilled through between the two tunnels which supplies brine to the opposite side of the excavation face and is used to check the spacing between the tunnel centre lines, the chainage and the elevation.

2.0.17 Freezing hole spacing: the centre-to-centre distance between two adjacent freezing holes.

2.0.18 Refrigerator: the device installed inside the freezing hole to circulate the refrigerant and exchange heat with the strata. The refrigerator consists of the freezing pipe and of the feeding pipe placed inside it.

2.0.19 Pressure release hole: a hole used to judge the closing of the freezing wall and to release the frost heaving pressure of the strata.

2.0.20 Temperature observation hole: a borehole arranged within the freezing wall and within the temperature drop zone for the installation of temperature sensors to monitor the temperature distribution of the strata at the various stages.

2.0.21 Bore hole inspection: an inspection hole used to check the freezing effect of the rock and soil mass and of the interface between the rock and soil mass and the retaining structure.

2.0.22 Deviational measurement: the operation of measuring the deviation value and the deviation direction of a borehole at different depths.

2.0.23 Deepness measurement: the operation of measuring the actual depth of a borehole.

2.0.24 Freezing station: the place where the refrigerating equipment and facilities are installed together. The refrigeration station is made up mainly of the refrigerant circulation system, the cooling medium circulation system such as the brine system, the cooling water circulation system and the power supply system.

2.0.25 Segment: the basic unit of the precast lining ring of a tunnel. Segments are of several types, including reinforced concrete segments, fibre concrete segments, steel segments, cast iron segments and composite segments.

2.0.26 Borehole orifice-pipe: the length of flanged steel pipe embedded at the position of the borehole before the normal drilling of the connecting passage; it is the basis on which the other devices are installed.