GB 50021-2001 (2009) Code For Investigation of Geotechnical Engineering [PDF]

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GB NATIONAL STANDARD OF THE PEOPLE'S REPUBLIC OF CHINA 中华人民共和国国家标准 GB 50021-2001



Code for Investigation of Geotechnical Engineering 岩土工程勘察规范 (2009 Edition)



Issued on January 10, 2002 Implemented on March 01, 2002 Issued by the Ministry of Construction of the People's Republic of China



Contents Foreword ................................................................................................................................1 1 General Provisions ..........................................................................................................4 2 Terms and Symbols.........................................................................................................4 3 Investigation Classification and Geotechnical Classification.........................................7 4 Basic Requirements of Engineering Investigations ......................................................16 4.1 Building Construction and Structures ..............................................................16 4.2 Underground Excavation .................................................................................23 4.3 Shoreside Engineering .....................................................................................27 4.4 Road and Overhead Network Engineering ......................................................29 4.5 Waste Disposal Engineering ............................................................................33 4.6 Nuclear Power Plant ........................................................................................38 4.7 Side Slope Engineering....................................................................................45 4.8 Foundation Excavation Engineering................................................................47 4.9 Pile Foundation ................................................................................................49 4.10 Foundation Treatment ......................................................................................52 4.11 Load Increasing and Protection for Pre-existing Building ..............................55 5 Adverse Geological Action and Geological Disaster....................................................58 5.1 Karst.................................................................................................................58 5.2 Landslide..........................................................................................................62 5.3 Dangerous Rock and Collapse .........................................................................64 5.4 Mud-rock Flow ................................................................................................65 5.5 Worked-out Section..........................................................................................67 5.6 Land Subsidence ..............................................................................................69 5.7 Seismic Effect of Site and Foundation.............................................................71 5.8 Active Faults ....................................................................................................73 6 Special Rock and Soil ...................................................................................................75 6.1 Collapsible Soil................................................................................................75 6.2 Red Clay...........................................................................................................77 6.3 Soft Soil ...........................................................................................................80 6.4 Fabricated Soil .................................................................................................82 6.5 Filling...............................................................................................................83 6.6 Perennial Frost .................................................................................................84 6.7 Expansion Rock and Soil .................................................................................88 6.8 Brine Salting Rock and Soil.............................................................................91 6.9 Decayed Rock and Residual Soil.....................................................................93 6.10 Pollute Soil.......................................................................................................95 7 Groundwater .................................................................................................................98 7.1 Investigation Requirements of Groundwater ...................................................98 7.2 Mensuration for Hydrogeologic Parameter .....................................................99 7.3 Evaluation for Functions of Ground-Water ...................................................101 8 Engineering Geological Mapping and Survey............................................................103 9 Exploration and Sampling...........................................................................................106



9.1 9.2 9.3 9.4 9.5



General Requirements....................................................................................106 Drilling...........................................................................................................106 Costeening, Trenching and Cave Exploration ...............................................109 Adopting of Geotechnical Samples ...............................................................109 Geophysical Exploration................................................................................112 10 In-situ Measurement ............................................................................................ 114 10.1 General Requirements....................................................................................114 10.2 Load Test........................................................................................................114 10.3 Statically Cone Penetration Test ....................................................................117 10.4 Circular Cone Dynamic Penetration Test.......................................................119 10.5 Standard Penetration Test...............................................................................120 10.6 Vane Shear Test..............................................................................................121 10.7 Pressurementer Test .......................................................................................122 10.8 Flat Dilatometer Test......................................................................................124 10.9 In-situ Direct Shear Test ................................................................................125 10.10 Wave Celerity Testing ....................................................................................127 10.11 Rock Mass In-Situ Stress Testing ..................................................................128 10.12 Testing with Shock Excitation Method..........................................................129 11 Indoor Test ...........................................................................................................131 11.1 General Requirements....................................................................................131 11.2 Soil Physical Property Test ............................................................................131 11.3 Soil Compress Consolidation Test .................................................................132 11.4 Soil Shear Strength Test .................................................................................133 11.5 Soil kinetic Property Test...............................................................................134 11.6 Rock Test........................................................................................................134 12 Assessment of Water and Soil Corrosivity ..........................................................136 12.1 Sampling and Testing.....................................................................................136 12.2 Corrosion Evaluation .....................................................................................137 13 In-situ Inspection and Monitoring .......................................................................141 13.1 General Provisions .........................................................................................141 13.2 Inspection and Monitoring for Foundation of Ground Base..........................141 13.3 Monitoring for Bad Geological Action and Geologic Hazard .......................143 13.4 Monitoring of Groundwater...........................................................................144 14 Geotechnical Engineering Analysis Assessment and Result Report....................147 14.1 General Provisions .........................................................................................147 14.2 Analyses and Adoption of Rock and Soil Parameter .....................................148 14.3 Basic Requirements of Outcome Report........................................................151 Annex A: Rock/soil Classification and Verification ..........................................................154 Annex B: Blow Count Correction of Taper Dynamic Sounding .......................................159 Annex C: Engineering Classification of Debris Flow .......................................................161 Annex D: Primary Distinguishing Method of Swelling Soil .............................................164 Annex E: Hydrogeologic Parameter Measurement Method..............................................165 Annex F: technical standards of the soil sampler ..............................................................167 Annex G: site environment type ........................................................................................168



Annex H Explanation of Wording .....................................................................................169



Announcement of Publishing the National Standard of Code for Investigation of Geotechnical Engineering No. 314 “Code for Investigation of Geotechnical Engineering” has been approved as a national standard with a serial number of GB 50021-2001 and will be implemented on July 1, 2009. Therein, Clauses 1.0.3, 4.1.18(1, 2, 3, and 4), 4.1.20 (1, 2, and 3), 4.8.5, 5.7.2, and 7.2.2 are compulsory provisions and must be enforced strictly. The former Code for Investigation of Geotechnical Engineering shall be abolished simultaneously. Partial revision clauses and specific content will be published on the recent publications “Engineering Construction Standardization” Ministry of Housing and Urban-Rural Development of the People’s Republic of China May 19, 2009



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Foreword According to the requirements of JIANBIAO [1998] No. 244 issued by the Ministry of Construction (MOC), “Code for Investigation of Geotechnical Engineering” GB 50021-1994 shall be revised. In the revision procedure, the chief development organization - MOC Integrated Investigation Research and Design Institute, together with the relevant investigation, engineering, research, teaching organizations, are consisted of a preparation group to extensively solicit for opinions nationwide and to prepare a special report on the key modified parts. In addition, the preparation group also has coordinated with the implementing and revising national standards involved for many times. Through repeated discussion and revision, the preparation group successively prepares first draft, exposure draft and approval draft for examining and finalizing. This Code basically remains the application scope, entire framework and primary coverage of 1994 Edition and makes some partial adjustments accordingly. Now, the Code comprises 14 chapters with the main contents as follows: 1. general provisions; 2. terms and symbols; 3. investigation classification and geotechnical classification; 4. basic requirements of engineering investigation; 5. adverse geological action and geological disaster; 6. special rock/soil; 7. groundwater; 8. engineering geological mapping and survey; 9. exploration and sampling; 10. in-situ testing; 11. indoor test; 12. Assessment of water and soil corrosion; 13. In-situ inspection and monitoring; 14. Geotechnical engineering analysis assessment and result report. The major revised contents include: 1. The investigation of " nuclear power plant" is added into the application scope; 2. "Terms and Symbols" chapter is added; 3. Hardness classification and integrity classification of rock, and basic quality classification of rock mass are added; 4. The investigation requirements of "buildings and structures" as well as "pile foundation" are revised; 5. The investigation provisions of "underground cavity", "shoreside project", " foundation pit project" and " foundation treatment" are revised; 6. The section of "tailing dam and ash-storing dam" is replaced with "investigation of waste disposal project";



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7. The chapter name of "in-situ stability" is replaced with " adverse geological action and geological disaster"; 8. Sections "site and foundation in the meizoseismal area" and "seismic liquidation" are incorporated into a section named as " seismic effect of site and foundation"; 9. "collapsible soil" and " red clay" have been revised; 10. Investigation requirements of " groundwater" are strengthened; 11. "Deep load test" and "flat chisel side-bulge test" are added. The context is compressed so as to highlight the technical rules that must be abided by in the investigation works as the execution reference of the engineering quality examination. In the future, this Code might be revised partially and the relevant partial revision information and content of provisions will be published on the magazine, Standardization of Engineering Construction. The provisions printed in bold type are compulsory ones and must be enforced strictly. All relevant organizations are kindly requested to sum up and accumulate your experiences in actual practices during the process of implementing this Code. The relevant opinions and advice, whenever necessary, can be posted or passed on to MOC Integrated Investigation Research and Design Institute (No. 177, Dongzhimennei Avenue, Beijing, 100007, China). The participating development organizations and staffs are as follows: Chief development organization: MOC Integrated Investigation Research and Design Institute Participating development organization: Beijing Investigation and Design Institute; Shanghai Geotechnical investigation and Design Institute; Central-South Investigation and Design Institute; State Power Corporation Power Planning and Design Institute; Investigation Institute of the Ministry of Machine Building; China Ordnance Industrial Geotechnical Investigation Design Institute;



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Tongji University; Chief drafting staffs: Gu Baohe, Gao Dazhao, Zhu Xiaolin, Li Shouzhi, Li Yaogang, Xiang Bo, Zhang Zaiming, Zhang Sumin, Zhou Hong, Mo Qunhuan, Dai Lianjun. Members of review expert panel: Lin Zaiguan, Wang Kai, Wang Shunfu, Wang Huichang, Biao Zhaoqing, Li Rongqiang, Deng Anfu, Su Yibing, Zhang Kuangcheng, Zhou Liangchen, Zhou Bingyuan, Zhou Xiyuan, Lin Songen, Zhong Liang, Gao Dai, Feng Lunian, Huang Zhilun, Fu Shifa, Fan Songhua, Wei Zhanghe The Ministry of Construction October, 2001



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1



General Provisions



1.0.1 This code is formulated with a view to implement the related national technical-economic policies in the geotechnical investigation activities, to accomplish state-of-the-art technology and economic feasibility, to ensure engineering quality and to improve investment benefit. 1.0.2 This Code is applicable to the geotechnical investigation of the engineering projects excluding hydraulic works, railway, highway, bridge and culverts. 1.0.3 Prior to the engineering and construction of the projects, the geotechnical investigation must be carried out according to the basic construction procedure. 1.0.3 A The geotechnical investigation shall, according to the requirements of each investigation stages of the engineering construction, exactly reflect the engineering geological conditions, and ascertain the adverse geological action and geological disaster. Through meticulous investigation and careful analysis, an investigation report presenting integral information and accurate assessment shall be provided. 1.0.4 For the geotechnical investigation, not only the requirements stipulated in this Code but also those in the current relevant ones of the nation shall be complied with. 2



Terms and Symbols



2.1 Terms 2.1.1 Geotechnical Investigation It's referred to the activities that according to the requirements of the construction projects, the geological, environmental and geotechnical engineering conditions of t he construction site shall be ascertained, analyzed and assessed so as to finalize the investigation documents. 2.1.2 Engineering Geological Mapping It's referred to adopt such methods as data gathering, survey visiting, geological survey and remote interpretation to ascertain the engineering geological elements of the site and to draw the corresponding engineering geological maps. 2.1.3 Geotechnical Exploration It's a mean of geotechnical investigation, including borehole surveying, costeaning, trenching exploration, test pitting, hole exploration, geophysical exploration and penetration sounding. 2.1.4 In-situ Testing The rock/soil mass is tested according to its position, and the primary structure, humidity and stress condition of the rock/soil shall be basically remained. 2.1.5 Geotechnical Investigation Report It's referred to the investigation technical document that is finalized through unscrambling, statistics, conclusion, analysis, assessment, proposing 4



2.1.6



2.1.7



2.1.8



2.1.9



2.1.10



2.1.11



2.1.12



2.1.13



engineering recommendations and forming a system as well as serving for the project construction service. In-situ Inspection Some measures shall be adopted to inspect the investigation achievement, or the effects of design and construction measures in site. In-situ Monitoring The change of the rock/soil property and groundwater, the stress/displacement of the rock/soil mass and the structures shall be systematically monitored and observed in site. Rock Quality Designation (RQD) The rock is drilled with 75 mm-diameter diamond bit and double barrel, and the coring is carried out continually; in the coring of the drilling run, the ratio between the total length of those drill-cores longer than 10 cm and the said footage per round trip shall be presented with percentage. Quality Classification Of Soil Samples The soil samples shall be classified according to the various disturbance degrees. Adverse Geological Actions It referred to those geologic actions that might endanger the projects due to the internal earth force or external earth force. Geological Disaster It referred to the event that endangers to safety of person, properties, works or environment due to the adverse geological actions. Ground Subsidence/land Subsidence It's referred to the land subsidence in large area, which is generally caused by the regional conical depression due to excessive groundwater abstraction. The large area of underground mining cavity and the deadweight collapse of loess also can result in ground subsidence. Standard Value of a Geotechnical Parameter



2.2 Symbol 2.2.1



Physical property and granulometric composition of rock/soil



e——Porosity ratio; IL——Liquidity index; Ir——Plasticity index; n ——Porosity; Sr——Saturation; ω——Moisture content, water ratio; ωL——Liquid limit; ωP——Plastic limit; Wu——Organic content; Y——Gravimetric density (absolute density); 5



ρ——Mass density (density); ρd——Dry density. 2.2.2 Rock/soil deformation parameters a——Compression coefficient; Cc——Compression index; Ce——Recompression index; Cs——Swelling index; ch——Horizontal consolidation coefficient; cv——Vertical consolidation coefficient; Eo——Deformation modulus; ED——Side expansion modulus; Em——Lateral pressure modulus; Es——Compression modulus; G——Shear modulus; Pc——Preconsolidation pressure. 2.2.3 Rock/soil intensive parameter c——Cohesive force; po——Proportional threshold pressure of load test, initial pressure of lateral-pressure test; pf——Critical edge pressure of lateral-pressure test; pL——Extreme pressure of lateral-pressure test; pu——Extreme pressure of load test; qu——Unconfined compression strength; τ——Shearing strength; ψ——Internal friction angle. 2.2.4 Penetration sounding and standard penetration test indicators Rf——Friction ratio of static sounding; fs——Lateral resistance of static sounding; N——Blow count of standard penetration test; N10——Blow count of lightweight taper dynamic sounding; N63.5——Blow count of heavy taper dynamic sounding; N120——Blow count of extra-heavy taper dynamic sounding; ps——Specific penetration resistance of static sounding; qc——Conehead resistance of static sounding. 2.2.5 Hydrogeologic parameters B——Leakage coefficient; k——Permeability coefficient; Q——Water inflow; R——Radius of influence; S——Coefficient of storage; T——Coefficient of transmissibility; u——Pore-water pressure 6



2.2.6 Other symbols Fs——Stability coefficient of side slope; ID——Soil texture index of side expansion; KD——Horizontal stress index of side expansion; pe——Expansibility; UD——Pore pressure index of side expansion;



ᇞFs——Extra collapse settlement;



s——Foundation settlement, load test settlement; St——Sensitivity; αw——Water content ratio of red clay; νp——Wave velocity of compression wave; νs——Wave velocity of shear wave; δ——Variation coefficient;



ᇞs——Total collapse;



μ——Poisson ratio; σ——Standard deviation.



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Investigation Classification and Geotechnical Classification



3.1 Geotechnical Investigation Classification 3.1.1 According to the engineering scale and characteristics, as well as the damages or impacts resulted from the geotechnical engineering problems, the geotechnical engineering can be classified into three levels: 1. First-level engineering: it's referred to the important engineering and the consequence hereof is extremely severe; 2. Second-level engineering: it's referred to general engineering that has severe consequence; 3. Third-level engineering: it's referred to the subordinate engineering that has slight consequence; 3.1.2



According to the complexity degree of sites, the sites can be classified into the following three levels:



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1. The first-level site (complex site) shall be compliant to one of the following conditions: 1) The building anti-seismic system is endangered; 2) The adverse geological actions are intensively evolved; 3) The geological environment has already been intensively damaged or possibly suffers from intensive damage; 4) There is multilayer groundwater, Karst fissure water that might impact the project or the other geohydrologic conditions are complex, so it's necessary to specially study the site. 2. The second-level site (moderate complex site) shall be compliant to one of the following conditions: 1) The building anti-seismic system is in adverse situation; 2) The adverse geological actions are generally evolved; 3) The geological environment has already been damaged to a general extent or possibly suffers from general damage; 4) The torography and terrain are comparatively complex; 5) The foundation is located in the site under the groundwater level. 3. The third-level site (simple site) shall be compliant to one of the following conditions: 1) The earthquake protection intensity is equal to or less than 6, or the site is good for the building anti-seismic system; 2) The adverse geological actions are not evolved; 3) The geological environment is basically not damaged; 4) The torography and terrain are simple; 5) The groundwater has no impact to the engineering works; Note: 1. Starting from first level, the classification will gradually move to the second level and third level, and the one that meet the proper requirement firstly will be prevailing; in Clause 3.1.3, the foundation classification is also identified according to the this method; 2. The site that is good for, adverse to or hazardous to the building anti-seismic system will be classified according to the provisions of current national standard Code for Seismic Design of Building (GB 50011).



3.1.3 According to the complexity degree of foundation, the foundations can be classified into the following three levels: 1. The first-level foundation (complex foundation) shall be compliant to one of the following conditions: 1) The rock/soil have various categories and the property is uneven but has huge variation; in this case, special treatment is needed;



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2) Special rock/soil features severe collapse, expansion, brining and pollution as well as other complex conditions, it's necessary to carry out special treatment. 2. The second-level foundation (moderate complex foundation) shall be compliant to one of the following conditions: 1) The rock/soil has various category and the property hereof is uneven and shows comparatively large change; 2) The special rock/soil out of the provisions of Item 1. 3. The third class-level foundation (simple foundation) shall be compliant to one of the following conditions: 1) The rock/soil has single category and the property hereof is uniform and shows no large change; 2) No special rock/soil at all. 4. According to the works' importance level, site complexity and foundation complexity, the geotechnical investigation can be classified according to the following conditions: Class A has one or more first-level items among works' importance, site complexity and foundation complexity; Class B is referred to theses investigation projects that are excluded from Class A and Class C; For Class C, the works' importance, site complexity and foundation complexity are in third level. Note: the first-level engineering work built on the rocky ground, if the site complexity and foundation complexity are all third-level, then the geotechnical investigation can be classified as Class B.



3.2



Classification and Verification of Rock



3.2.1



In the geotechnical investigation procedure, the geologic name and weathering degree of the rock shall be verified, and the rock hardness degree, rock mass integrity degree and rock mass initial quality shall be classified.



3.2.2



The rock hardness degree, rock mass integrity degree and rock mass initial quality shall be classified according to the provisions of Table 3.2.2-1- Table 3.2.2-3. Table 3.2.2-1: Rock Hardness Degree Classification 9



Hardness intensity



Harder rock



hard rock



Soft rock



Softer rock



Softest rock



Saturated uniaxial compressive strength (Mpa)



fr＞60



60≥fr＞30



30≥fr＞15



15≥fr＞5



fr≤r＜5



Note: 1.



The standard engineering rock mass classification shall be compliant to the provisions of GB 50218.



2.



If the rock mass integrity degree is extremely breaking, then it's unnecessary to carry out any hardness classification.



Table 3.2.2-2 Rock Mass Integrity Degree Classification Integrity degree



More integral



Integral



Breaking



More breaking



Most breaking



Integrality index



0.75＞



0.75~0.55



0.55~0.35



0.35~0.15



＜0.15



Table 3.2.2-3: Rock Mass Initial Quality Classification More Integral Breaking More integral Breaking



Integrity degree Hardness degree



Harder rock Hard rock Soft rock Softer rock Softest rock



I II III IV V



II III -IV IV V



III IV IV V V



IV IV V V V



Most Breaking V V V V V



3.2.3



Hardness degree and completion degree of rock are classified in accordance with Table A.0.1 and Table A.0.2 of Annex A in this standard, if it is lack of relative testing data. The division of rock weathering degree may be taken in accordance with Table A.0.3 of Annex A in this standard.



3.2.4



If the softening coefficient is equal to or less than 0.75, the rock shall be defined as softened rock; if rocks have particular composition, special construction or distinctive feature, the rocks shall be defined as special rocks, such as soluble rock, swelling rock, disintegrative rock and salinized rock.



3.2.5



The description for rocks shall consist of geologic age, geologic name, the degree of weathering, color, essential minerals, structure, contexture and rock quality designation (RQD). For sedimentary rock, sediment granular size, shape, agglutinate composition and the degree of cementation shall be emphasized; mineral crystallographic dimension and the degree of crystallinity shall be emphasized for magmatic rock. 10



In accordance with rock quality designation (RQD), rocks are classified as perfect (RQD>90), good (RQD = 75~90), poor (RQD = 50~75), bad (RQD = 25~50) and worse (RQD