NB/T 10311-2019Code for design of wind turbine foundations for onshore wind power projects (English PDF)

Foreword

This document was issued on 4 November 2019 by the National Energy Administration of the PRC and takes effect on 1 May 2020.

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 code has been formulated by the drafting group in accordance with the requirements of the 'Notice of the National Energy Administration on Issuing the First Batch of Formulation (Revision) Plans for Energy Sector Industry Standards in 2014' (Guo Neng Ke Ji [2014] No. 298), on the basis of extensive investigation and research, a careful summary of practical experience and the wide solicitation of opinions.

The main technical contents of this code are: geotechnical properties of the ground; loads and combinations of load effects; ground calculations; foundation design; ground treatment; inspection and monitoring.

This code is administered by the National Energy Administration. It was proposed by, and its routine management is the responsibility of, the China Renewable Energy Engineering Institute (General Institute of Hydropower and Water Resources Planning and Design). The Sub-Technical Committee for Wind Farm Planning and Design of the Wind Power Standardization Technical Committee of the Energy Industry is responsible for the interpretation of the specific technical contents. Comments or suggestions arising during implementation should be sent to the China Renewable Energy Engineering Institute (address: No. 2 Liupukang Beixiaojie, Xicheng District, Beijing; postcode 100120).

Chief editing organizations of this code: PowerChina Northwest Engineering Corporation Limited; China Renewable Energy Engineering Institute (General Institute of Hydropower and Water Resources Planning and Design).

Participating organizations of this code: PowerChina Huadong Engineering Corporation Limited; Xinjiang Goldwind Science and Technology Co., Ltd.; Beijing University of Civil Engineering and Architecture; China University of Geosciences (Wuhan).

Chief drafters of this code: Shen Kuanyu, Li Zhenzuo, Tian Weihui, Hu Yongzhu, Yu Huafeng, Zhang Liying, Cong Ou, Du Xiaokai, Zhong Jianping, Cui Zhenlei, Ji Hao, Tang Qunyi, Huo Hongbin, Liu Rongli, Hao Huageng, Wang Zhishuo, Wang Liping, Fu Zhiqiang, Liu Wei, Zhu Lei, Chen Jinjun, Liu Xiaofeng, Gao Jianhui.

Chief reviewers of this code: Sun Baoping, Yan Yongpu, Xie Hongwen, Lin Yifeng, Huang Chunfang, Liang Huarong, Zhong Tingying, Lai Fuliang, Li Qingshi, Ma Zhaorong, Li Xin, Shi Guangbin, Dai Kaoshan, Yu Jialin, Zhu Jianye, Yu Liang, Zhao Guogang, He Guangling, Cao Guangqi, Fan Junxi, Zhao Tie, Piao Ling, Li Shisheng.

Publication and Approval Data

NB/T 10311-2019 is an energy industry standard of the People's Republic of China, designated on the cover with the classification letter P. It was issued on 4 November 2019 and came into force on 1 May 2020.

The standard was promulgated by Announcement No. 6 of 2019 of the National Energy Administration, which approved 384 energy industry standards headed by the 'Technical Code for Electrical Prospecting of Hydropower Projects' (Annex 1), 48 English versions of energy industry standards headed by the 'Technical Guide for Rock-Filled Concrete Dams' (Annex 2), No. 1 amendment sheets to 7 energy industry standards headed by the 'Technical Code for Environmental Impact Assessment of Wind Farm Projects' (Annex 3), and abolished 5 energy industry standards and plans headed by the 'Charging Standard for Survey and Design of Wind Farm Projects' (Annex 4). The announcement is dated 4 November 2019.

In Annex 1, the Catalogue of Industry Standards, this code is entered under serial number 88 as NB/T 10311-2019, with the approval date 2019-11-04 and the implementation date 2020-05-01. The columns for the superseded standard and for the adopted international standard number are blank, which shows that this code is a newly formulated standard and does not replace any earlier standard.

Chief editing department: China Renewable Energy Engineering Institute (General Institute of Hydropower and Water Resources Planning and Design). Approving department: National Energy Administration. Date of implementation: 1 May 2020.

Published and distributed by China Water and Power Press, Building D, No. 1 Yuyuantan South Road, Haidian District, Beijing 100038; printed by Qingsong Yongye (Tianjin) Printing Co., Ltd.; sold through Xinhua bookstores and related publication sales outlets throughout China.

Printing data of the first edition: format 140 mm by 203 mm, 32-mo, 3.75 printed sheets, 101 thousand characters; first edition May 2020, first printing May 2020; print run 0001 to 2000 copies; book number 155170-599; list price 100.00 yuan.

Classification data shown on the cover: International Classification for Standards (ICS) 27.180, covering wind turbine systems and other alternative energy sources, and Chinese Standard Classification Code P 61 of the engineering construction group.

Structure of the Code (from the official Contents)

Chapter 1, General Provisions, starting at page 1, sets out the purpose, the scope of application and the relationship of this code with other current national standards.

Chapter 2, Terms, starting at page 2, defines the nine terms used throughout the code, covering the five foundation types, the two embedded tower connectors and the two categories of turbine load.

Chapter 3, Basic Requirements, starting at page 3, is divided into General Requirements (page 3), Ultimate Limit State Calculation (page 5), Serviceability Limit State Verification (page 6), Durability Requirements (page 6) and Materials (page 8).

Chapter 4, Geotechnical Properties of Ground, starting at page 14, is divided into Rock and Soil Classification (page 14) and Geotechnical Properties (page 17).

Chapter 5, Loads and Action Effect Combinations, starting at page 20, is divided into Loads (page 20), Load Conditions (page 20), Action Effect Combinations (page 21) and Coefficients and Partial Factors (page 23).

Chapter 6, Ground Calculations, starting at page 26, is divided into General Requirements (page 26), Bearing Capacity Calculation (page 27), Compression Capacity Calculation (page 29), Deformation Calculation (page 33), Stability Calculation (page 35) and Ground Foundation Dynamic Stiffness Verification (page 37).

Chapter 7, Wind Turbine Foundation Design, starting at page 38, is the longest chapter and is divided into General Requirements (page 38), Spread Foundation (page 39), Raft Foundation (page 43), Rock Foundation with Prestressed Bolts (page 45), Pile Foundation (page 48), Prestressed Tubular Foundation (page 58) and Check of Connection Between Tower Connector and Foundation (page 63).

Chapter 8, Ground Treatment, starting at page 65, is divided into General Requirements (page 65), Soil-Rock Composite Ground (page 65), Compacted Fill Ground (page 66), Karst Ground (page 67) and Soft Ground (page 68).

Chapter 9, Inspection and Monitoring, starting at page 69, is divided into General Requirements (page 69), Inspection (page 69) and Monitoring (page 70).

The back matter comprises the Explanation of Wording in This Code (page 72), the List of Quoted Standards (page 73) and the Addition: Explanation of Provisions (page 75), the last of which gives the clause-by-clause commentary of the drafting group.

1 Scope

NB/T 10311-2019 is the Chinese design code for the foundations of onshore wind turbines. A turbine foundation carries a comparatively light vertical load under a very large overturning moment that reverses with the wind, applied several million times over the machine's life - so it is governed by rotational stiffness, by the stability of the whole block against overturning and by fatigue at the connection, not by bearing pressure. The code sets the general provisions, the defined terms and symbols, then the basic requirements: the design service life, the limit states, the partial factors, and the loads supplied by the turbine manufacturer together with the load combinations for normal, extreme, fault and seismic conditions. It then covers the site investigation needed and the foundation types in turn - the gravity spread foundation in its circular and polygonal forms, the piled foundation with cast-in-place or precast piles and its cap, the rock-anchored foundation used where competent rock is near the surface, and the beam-and-slab and bucket variants. For each it gives the geometry, the stability checks against overturning, sliding and bearing, the settlement and rotational stiffness requirement, and the structural design with reinforcement detailing. The embedded ring or anchor cage connection to the tower receives its own treatment, with the fatigue and pre-tension checks that govern it. Construction requirements, waterproofing, backfill and the monitoring of settlement and tilt close the code.

1.0.1 This code is formulated in order to standardize the design of wind turbine generator foundations in onshore wind farm projects, and to achieve designs that are safe and suitable, economically reasonable, technically advanced and environmentally friendly.

1.0.2 This code is applicable to the design of wind turbine generator foundations in onshore wind farm projects.

1.0.3 In addition to complying with this code, the design of wind turbine generator foundations in onshore wind farm projects shall also comply with the provisions of the relevant current national standards.

2 Terms

2.0.1 Spread foundation. A foundation composed of a pedestal and a base slab, which spreads the pressure transmitted to the ground.

2.0.2 Raft foundation. A foundation composed of a pedestal, ribbed beams and a base slab acting together, which spreads the pressure transmitted to the ground.

2.0.3 Rock foundation with prestressed bolts. A foundation composed of prestressed anchor bolts anchored into rock acting together with a concrete cap.

2.0.4 Pile foundation. A foundation composed of foundation piles installed in rock and soil acting together with a cap connected to the tops of the piles.

2.0.5 Prestressed tubular foundation. A foundation composed of a circular prestressed concrete tube together with plain concrete backfilled around its outer side.

2.0.6 Foundation ring. A steel-tube type embedded connector used for the connection between the tower and the foundation.

2.0.7 Bolted cage. A ring-shaped, cage-type embedded connector composed of high-strength prestressed anchor bolts, used for the connection between the tower and the foundation.

2.0.8 Normal operating load. The most unfavourable load effect among the load conditions determined by combining the normal design situation of the wind turbine generator with normal external conditions.

2.0.9 Extreme load. The most unfavourable load effect among all the load conditions of the wind turbine generator.