NB/T 10075-2018Specification for karst engineering geological investigation of hydropower projects (English PDF)

Foreword

This document was issued on 29 October 2018 by the National Energy Administration of the PRC and takes effect on 1 March 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 27.140, Chinese classification P 59.

It replaces DL/T 5338-2006, which is superseded.

This Specification has been revised in accordance with the requirements of the Notice of the National Energy Administration on Issuing the Second Batch of the 2014 Plan for the Preparation and Revision of Sector Standards in the Field of Energy (Guo Neng Ke Ji [2015] No. 12). The drafting group carried out extensive investigation and research, summarised practical experience in earnest, and revised the Specification on the basis of a wide solicitation of comments.

The main technical contents of this Specification are: basic requirements; engineering geological investigation of karst for the reservoir; engineering geological investigation of karst for the dam site; engineering geological investigation of karst for underground chambers; and the result report.

The main technical changes introduced by this revision are listed in the items that follow.

Terms such as soluble rock, clastic rock corrosion, structure gap and rate of hole drilling have been added.

Analysis and assessment of the influence of underground chamber excavation on the surrounding hydrogeological environment has been added.

The contents of the result report have been expanded.

The following contents have been added: division of the development degree of karst and of dissolved weathering in carbonate rock areas; types of hydrodynamic conditions of karst valleys; curve types of karst groundwater level; the survey table of karst features; the survey table of karst springs; and the grading of karst declogging and mud-bursting.

The Chinese term rendered as kasite in the former specification has been replaced throughout by the term yanrong, that is, karst.

The former clause on the analysis and assessment of submergence-related waterlogging problems has been revised into the analysis and assessment of karst waterlogging problems, and the former clause on the analysis and assessment of dam foundation stability, leakage and leakage stability problems has been revised into the analysis and assessment of dam foundation stability and leakage problems.

The former appendix on the types of carbonate rock layers and groups has been revised into the layer and group types of soluble rock, and the former appendix on the hydrogeological structure types of valley karst has been revised into the hydrogeological structure types of karst.

The reduction factor of external water pressure has been revised.

This Specification is under the administration of the National Energy Administration. It was proposed by, and is under the routine administration of, the China Renewable Energy Engineering Institute. The Standardization Technical Committee for Hydropower Investigation and Design of the Energy Sector is responsible for the interpretation of its specific technical contents.

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

Chief development organisations of this Specification: PowerChina Kunming Engineering Corporation Limited and the China Renewable Energy Engineering Institute.

Participating development organisation of this Specification: PowerChina Guiyang Engineering Corporation Limited.

Chief drafting personnel of this Specification: Wang Wenyuan, Wang Kun, Guo Jiazhong, Yu Bo, Wang Huiming, He Zhipan, Li Gang, Zheng Kexun, Wang Yuansheng and Guo Decun.

Chief review personnel of this Specification: Peng Tubiao, Yang Jian, Guo Yihua, Shan Yegang, Liu Chang, Li Xuezheng, Chen Weidong, Mi Yingzhong, Guo Weixiang, Wang Liangtai, Yi Zhijian, Li Sunquan, Gong Hailing, Lu Dongliang and Li Shisheng.

Publication and Approval Data

Designation of the standard as printed on the cover: NB/T 10075-2018, an energy sector standard of the People's Republic of China.

Chinese title: Shuidian Gongcheng Yanrong Gongcheng Dizhi Kancha Guicheng. Official English title printed on the cover: Specification for Karst Engineering Geological Investigation of Hydropower Projects.

Classification data printed on the cover: ICS 27.140; Chinese Standard Classification Code P 59; record filing number J520-2018; sector classification letter P.

The Specification replaces DL/T 5338-2006 and was issued on 29 October 2018 and put into implementation on 1 March 2019.

Chief editing department: the China Renewable Energy Engineering Institute. Approving department: the National Energy Administration. Date of entry into force: 1 March 2019.

Issuing authority printed on the cover: the National Energy Administration. Publisher: China Water and Power Press, Beijing, 2019.

The Specification was approved by Announcement No. 12 of 2018 of the National Energy Administration, dated 29 October 2018.

That announcement was issued under the Notice of the National Energy Administration on Issuing the Administrative Measures for Sector Standardization in the Field of Energy (Trial) and the Detailed Rules for Their Implementation (Guo Neng Ju Ke Ji [2009] No. 52).

Under that announcement the National Energy Administration approved and issued 204 sector standards, comprising 54 energy standards (NB), 8 petrochemical standards (NB/SH) and 142 petroleum standards (SY), the first of which is the standard on mine-use air-cooled adjustable-speed magnetic couplings.

In the catalogue of sector standards annexed to the announcement, this Specification appears as serial number 30, standard number NB/T 10075-2018, superseded standard DL/T 5338-2006, approval date 29 October 2018, implementation date 1 March 2019. No adopted international standard reference is shown.

Structure of the Document

The Specification is organised in seven chapters followed by nine appendices, a wording explanation, a list of quoted standards and an explanation of provisions; the English chapter and appendix titles reproduced here are those printed in the official Contents of the standard.

Chapter 1 General Provisions, page 1, and Chapter 2 Terms, page 2, establish the purpose, the scope and the nineteen defined terms.

Chapter 3 Basic Requirements, page 4, fixes the task, the technical methods and the working steps of the investigation.

Chapter 4 Engineering Geological Investigation of Karst for Reservoir, page 5, is divided into 4.1 General Requirements, 4.2 Investigation Contents, 4.3 Investigation Methods, 4.4 Analysis and Assessment for Leakage and 4.5 Analysis and Assessment for Karst Waterlogging.

Chapter 5 Engineering Geological Investigation of Karst for Dam Site, page 17, is divided into 5.1 General Requirements, 5.2 Investigation Contents, 5.3 Investigation Methods and 5.4 Analysis and Assessment for Foundation Stability and Leakage.

Chapter 6 Engineering Geological Investigation of Karst for Underground Chamber, page 24, is divided into 6.1 General Requirements, 6.2 Investigation Contents, 6.3 Investigation Methods and 6.4 Analysis and Assessment for Surrounding Rock Stability and Leakage.

Chapter 7 Result Report, page 31, is divided into 7.1 Special Result Report and 7.2 Drawings and Attachments.

Appendix A Layer and Group of Soluble Rock, page 33, and Appendix B Division of Development Degree of Karst and Dissolved Weathering in Carbonate Rock Area, page 34, support the classification work required by 4.2.3.

Appendix C Types of Hydrodynamic Conditions of Karst Valley, page 36, Appendix D Curve Types of Karst Groundwater Level, page 38, and Appendix E Hydrogeological Structure Types of Karst, page 40, support the hydrogeological assessment.

Appendix F Survey Table of Karst Features, page 42, and Appendix G Survey Table of Karst Springs, page 44, provide the standard field recording forms.

Appendix H Grading of Karst Declogging and Mud-bursting, page 45, and Appendix J Reduction Factor of External Water Pressure in Karst Area, page 47, support the underground chamber assessment of Chapter 6.

The closing material comprises Explanation of Wording in This Specification, page 48, List of Quoted Standards, page 49, and Addition: Explanation of Provisions, page 51.

The standards quoted in the text of Chapter 4 are GB 50287, DL/T 5410 and DL/T 5336; the full list of quoted standards is given on page 49 of the standard.

The standard is printed in Chinese; the Contents page and the cover carry an official English rendering of the title, of the chapter headings and of the appendix headings, which has been followed word for word above.

1 Scope

NB/T 10075-2018 governs the engineering geological investigation of karst on hydropower projects, replacing DL/T 5338-2006. Karst - the caves, conduits, sinkholes and buried channels dissolved into limestone and dolomite - is the single most awkward ground condition a Chinese dam engineer meets, because south-west China, where most of the hydropower is, is also where the carbonate rock is. A karst conduit can drain a reservoir into the next valley, swallow a grout curtain, flood a tunnel without warning or collapse under a foundation. The specification sets the scope and depth of investigation at each design stage, from planning through feasibility to detailed design and construction. It covers the survey and mapping of karst features at the surface, the geophysical exploration and drilling used to find them at depth, cave exploration and tracer testing to establish where the water goes, the hydrogeological observation of springs and groundwater levels, and the laboratory work on rock and water. It then sets out the assessment: the classification of karst development, the evaluation of reservoir leakage and of seepage around dam abutments, the stability of foundations and slopes over karst, the water inrush risk in tunnels, and the karst collapse hazard. Treatment design and the monitoring that verifies it, together with the investigation report and its drawings, close the specification.

Chapter 1 sets out the purpose, the field of application and the relationship of this Specification with other standards in force.

1.0.1 This Specification is formulated in order to standardise the working contents, methods and technical requirements of karst investigation for hydropower projects and to ensure the quality of the investigation results.

1.0.2 This Specification applies to the geological investigation and assessment of hydropower projects in soluble rock areas.

1.0.3 In addition to complying with this Specification, karst engineering geological investigation of hydropower projects shall also comply with the provisions of the relevant national standards currently in force.

2 Terms

Chapter 2 establishes nineteen terms with their definitions; the English equivalents given below are those printed alongside the Chinese entries in the standard.

2.0.1 soluble rock: rock that can undergo dissolution in an aqueous solution.

2.0.2 karst: the general designation of the dissolution of soluble rock by water and of the various geological phenomena and landforms produced thereby.

2.0.3 karst process: the comprehensive geological action of water upon soluble rock whose principal characteristic is chemical dissolution.

2.0.4 karst phenomena: the various surface and subsurface phenomena produced by the karst process.

2.0.5 clastic rock corrosion: the dissolution phenomenon affecting the soluble constituents contained in clastic rock.

2.0.6 rate of karstification: a quantitative index of the scale and density of karst voids within a given range; it may be divided into point karstification rate, linear karstification rate, areal karstification rate, volumetric karstification rate and borehole karst exposure rate.

2.0.7 rate of karst filling: the percentage ratio of the volume of filling material to the volume of the karst void form; it may be divided into fully filled, half filled and slightly filled.

2.0.8 bare karst: karst exposed at the ground surface.

2.0.9 covered karst: karst covered by Quaternary deposits.

2.0.10 buried karst: karst buried beneath non-soluble rock.

2.0.11 karst depression: a closed negative landform with a flat bottom and a relatively large area, formed by dissolution.

2.0.12 karst basin: a large karst depression covered by Quaternary deposits.

2.0.13 karst valley: an elongated, strip-shaped karst depression.

2.0.14 karstic network: a system of interconnected karst caves.

2.0.15 karst aquifer: a soluble rock stratum containing groundwater.

2.0.16 karst spring: a natural outcrop of karst water at the ground surface.

2.0.17 karst declogging: the phenomenon in which groundwater in karst strata, exposed by human activity or under the influence of natural factors, produces a large inrush of water, frequently accompanied by an outflow of mud and sand.

2.0.18 structure gap: the condition in which soluble rock strata of different horizons are brought into one and the same karstified stratum through fault displacement.

2.0.19 rate of hole drilling: the percentage of boreholes that expose karst caves and fissures out of the total number of exploratory boreholes.

3 Basic Requirements

3.0.1 The task of karst engineering geological investigation for hydropower projects is to ascertain the laws of karst development and the hydrogeological and engineering geological conditions of the reservoir and of the project area, to assess their influence on the project and on the environment, and to put forward reasonable conditions of utilisation and recommendations on engineering treatment measures.

3.0.2 The investigation and assessment of karst engineering geological problems of hydropower projects shall be carried out on the basis of an investigation of the karst development characteristics and hydrogeological conditions of the region.

3.0.3 Karst engineering geological investigation of hydropower projects shall select investigation and testing methods reasonably in the light of the actual topographic and geological conditions. The principal investigation and testing methods are those listed in the following items.

3.0.3 item 1 Geological mapping and survey, and remote sensing interpretation.

3.0.3 item 2 Drilling exploration, adit exploration, pit and trench exploration, geophysical exploration and the like.

3.0.3 item 3 Borehole water pressure tests and borehole pumping tests; stable water level observation; large-drawdown shaft pumping tests or multi-borehole group pumping tests; tracer tests, that is connectivity tests; water balance analysis; study of the groundwater seepage field; study of the water temperature field; study of the hydrochemical field and of the water isotope field; cave-plugging water-raising tests; long-term dynamic observation of groundwater; and terrestrial hydrology methods.

3.0.4 Karst engineering geological investigation of hydropower projects shall be carried out in accordance with the steps listed in the following items.

3.0.4 item 1 Preparatory work. Data are first collected and the karst process and the general laws of karst development are analysed; a work outline, an operating plan and the investigation methods are then drawn up.

3.0.4 item 2 Field work. Indoor remote sensing interpretation is performed, after which field geological survey and mapping, geophysical testing, exploration and hydrogeological testing are carried out in order to ascertain the stratigraphic lithology, the geological structure, the laws of karst development and the structural characteristics and occurrence laws of karst hydrogeology; the work passes to indoor compilation only after the field results have been accepted as qualified.

3.0.4 item 3 Data compilation. The analysis and assessment of karst hydrogeological and engineering geological conditions is completed, and the research results together with the accompanying drawings are submitted.

The chapter therefore fixes the task, the prerequisite regional basis, the admissible technical means and the three-stage working procedure that govern every investigation performed under this Specification.

The methods listed in 3.0.3 cover surface survey, subsurface exploration and in-situ hydrogeological testing, so that the karst hydrodynamic field can be characterised and not merely the karst forms observed.

The sequence fixed in 3.0.4 makes the acceptance of field results a condition precedent to indoor compilation, which is the quality control point of the whole investigation cycle.

4 Engineering Geological Investigation of Karst for Reservoir

Section 4.1 General Requirements.

4.1.1 Karst engineering geological investigation for the reservoir shall assess the karst engineering geological problems of the reservoir on the basis of ascertaining the laws of karst development and the karst engineering geological conditions of the reservoir area, and shall provide an engineering basis for the design of reservoir treatment.

4.1.2 Karst engineering geological investigation for the reservoir shall concentrate on ascertaining the problems of karst leakage and of karst waterlogging of the reservoir.

4.1.3 The working scope of karst engineering geological investigation for the reservoir shall include the distribution area of the soluble rock strata that may give rise to reservoir leakage, waterlogging and similar effects, and in particular the recharge, runoff and discharge areas of karst conduit water having a close hydraulic connection with the reservoir and with the downstream river reach. For a pumped storage power station, in addition to the upper and lower reservoirs, the scope shall also include the range extending from the elevation of the soluble rock distribution around the upper reservoir down to the erosion surface of the lower reservoir valley.

4.1.4 Karst engineering geological investigation of the reservoir area shall comply with the relevant provisions of the national standards currently in force: Code for Engineering Geological Investigation of Hydropower Projects GB 50287, Code for Engineering Geological Investigation of Small and Medium Hydropower Projects DL/T 5410, and Technical Specification for Engineering Geological Investigation of Reservoir Areas of Hydropower and Water Resources Projects DL/T 5336.

Section 4.2 Investigation Contents.

4.2.1 The main contents of karst engineering geological investigation for the reservoir shall include the topography and landforms, the soluble rock and its layer and group types, the geological structure, the karst phenomena and the karst hydrogeological conditions.

4.2.2 The investigation of topography and landforms shall comply with the requirements given in the following items.

4.2.2 item 1 Investigate the regional topography and landforms, the distribution and characteristics of the water system, the planation surfaces, the state of terrace development, the evolution of the hydrographic network and the developmental history of the valley.

4.2.2 item 2 Investigate the topographic characteristics of important sections such as the reservoir, low saddles, river bends, low adjacent valleys, the river reach downstream of the dam and the watershed divides, and determine the elevation of the knick points of the valley.

4.2.3 The investigation of soluble rock and of its layer and group types shall comply with the requirements given in the following items.

4.2.3 item 1 Investigate the regional stratigraphy; ascertain the horizon of the soluble rock strata and their contact relationships with the overlying and underlying strata, and the distribution of non-karstified rock masses and of loose deposits.

4.2.3 item 2 Investigate the chemical composition and the rock-forming minerals of the soluble rock types.

4.2.3 item 3 Investigate the dissolution types of the soluble rock.

4.2.3 item 4 Investigate the layer and group types of the soluble rock strata, their degree of permeability and their karst development characteristics. The classification of the layer and group types of soluble rock shall comply with the provisions of Appendix A of this Specification.

4.2.3 item 5 Ascertain, within each layer and group type, the compositional relationship between karstified and non-karstified strata; ascertain whether relatively impermeable rock strata exist within permeable rock strata, or whether weakly karstified rock strata exist within strongly karstified rock strata, together with the characteristics of their occurrence and combination and their influence on the hydrogeological conditions.

4.2.3 item 6 Investigate the variations in the lithology and lithofacies of the soluble rock and their influence on the classification of layer and group types and on the intensity of karst development.

4.2.4 The investigation of geological structure shall comply with the requirements given in the following items.

4.2.4 item 1 Investigate the regional structural position; ascertain the development characteristics of folds and fracture structures; determine the extension of the rock strata distributed in the reservoir towards low adjacent valleys or towards the river reach downstream of the dam; ascertain the distribution of the relatively impermeable layers between the soluble rock strata and the hydraulic connections between them; and judge preliminarily whether leakage problems exist and at which locations leakage may occur.

4.2.4 item 2 Ascertain whether a structure gap exists in the soluble rock strata.

4.2.4 item 3 Ascertain the position and character of faults and of their influence zones, and the degree of karst development in their vicinity.

4.2.4 item 4 Investigate the mechanical property categories of the faults and the differences in the intensity of karst development between faults of different character.

4.2.4 item 5 Investigate the attitude of structural planes such as bedding planes and faults and their relationship with the overall direction of groundwater circulation. For faults whose strike coincides with, or is close to, the overall direction of groundwater movement, and for structural planes extending along that direction, longitudinal tension fissures in the axial parts of folds and their intersection positions, attention shall be paid to investigating whether caves or conduits of relatively large scale exist.

4.2.4 item 6 Investigate the intensity of karst development at positions such as the plunging ends of anticlines, the upturned ends of synclines and the hinge zones of large fold structures.

The remaining provisions of Chapter 4, namely 4.3 Investigation Methods, 4.4 Analysis and Assessment for Leakage and 4.5 Analysis and Assessment for Karst Waterlogging, occupy pages 9 to 16 of the standard and are not reproduced in this preview.