State regulations on geological survey works

State regulations on geological survey works

State regulations on geological survey works

26/05/2021

Standard 9363:2012 guides several technical requirements in surveying for high-rise buildings. Some important and necessary contents such as classification of high-rise buildings, instructions on the arrangement of the borehole network, and borehole depth corresponding to the size of the work and the construction stages.

NATIONAL STANDARDS

TCVN 9363:2012

SURVEY FOR CONSTRUCTION – GEOTECHNICAL SURVEY FOR HIGH RISE BUILDINGS

Building surveys – Geotechnical investigation for high rise building

Preface

TCVN 9363:2012 is converted from TCXDVN 194:2006 according to the provisions of Clause 1, Article 69 of the Law on Standards and Technical Regulations and point a Clause 1, Article 7 of Decree No. 127/2007/ND-CP dated August 1, 2007, of the Government detailing the implementation of several articles of the Law on Standards and Technical Regulations.

TCVN 9363:2012 compiled by the Institute of Construction Science and Technology - Ministry of Construction, proposed by the Ministry of Construction, appraised by the General Department of Standards, Metrology, and Quality, and published by the Ministry of Science and Technology.

SURVEY FOR CONSTRUCTION – GEOTECHNICAL SURVEY FOR HIGH RISE BUILDINGS

Building surveys – Geotechnical investigation for high-rise buildings.

SURVEY FOR CONSTRUCTION – GEOTECHNICAL SURVEY FOR HIGH RISE BUILDINGS

Building surveys – Geotechnical investigation for high rise building

 

1. Scope of application

This standard is the basis for making geotechnical survey plans for the design and construction of high-rise building foundations.

2. References

The following referenced documents are necessary for the application of this standard. For dated references, the version stated applies. For updated referenced documents, the latest version, including amendments and supplements (if any), applies.

TCVN 4419:1987, Survey for construction - Basic principles.

TCVN 9364:2012, High-rise buildings - Surveying techniques for construction work.

3. Terms and definitions

In this standard, the following terms and definitions are used:

3.1 High rise building

Houses and public buildings with more than 9 floors (refer to Appendix B).

3.2 Geotechnical investigation

Part of a construction survey to investigate, determine and evaluate geotechnical conditions for building houses and structures; Also consider the interaction of the geological environment with the houses and structures themselves during their construction and exploitation.

3.3 Geotechnical investigation program

Specify the composition, volume of survey work and technical requirements to be performed during the geotechnical survey. In addition, the geotechnical survey plan should present the implementation solution, schedule, and estimated cost of the survey work.

3.4 Borehole

Survey boreholes directly serve the design of construction works.

3.5 Geostructural borehole

Survey boreholes are used to capture the entire geotechnical conditions of the construction site. Control boreholes are usually deeper than conventional boreholes, but the number is much less.

4. General provisions

4.1. The task of geotechnical survey for the design and construction of the foundation of high-rise buildings shall be established by the design consultancy contractor and approved by the investor. The geotechnical survey plan is drafted by the surveying contractor based on geotechnical survey tasks and approved by the investor.

4.2 Geotechnical survey for high-rise buildings is carried out in stages corresponding to the design stages: a geotechnical survey in the pre-basic design stage, a geotechnical survey in the design stage. basis, a geotechnical survey in the engineering design stage and a geotechnical survey in the construction drawing design phase. Once the construction site has been determined, the survey phase before the basic design can be skipped.

4.3 Geotechnical investigation for high-rise buildings is associated with a general construction survey, according to TCVN 4419:1987.

4.4 Basis for making geotechnical survey plan

- Archives related to the area to be built: geological structure, topography, geomorphology, hydrogeology, issues of construction dynamics, physical and mechanical properties of soil and rock;

- Geotechnical survey tasks, data related to construction characteristics such as ground, structure, use formula.

4.5 Main issues to be solved in the geotechnical survey for high-rise buildings

4.5.1 Clarifying geological engineering conditions of the construction area, including geotectonic characteristics (stratigraphy, geological structure, tectonic); Topography - geomorphology; hydrogeology; Geodynamic processes and phenomena of works; Mechanical properties of soil and rock; Natural building materials.

4.5.2 In all cases, the location, and characteristics of the soil layer can carry a large or significant portion of the building load (referred to as the load-carrying layer).

4.5.3 When the load-carrying layer is relatively deep or deep, the pile foundation must be used to transmit the load, it is necessary to provide information on the distribution range and physical and mechanical properties of each soil layer through which the pile penetrates, coefficient of friction of the soil with the pile, the ability to generate negative friction on the pile in the case of using a friction pile and especially of the bearing soil layer under the tip of the pile in the case of using a supporting pile.

4.5.4 When the load-bearing layer is rock, it is necessary to clarify the degree of weathering and cracking, the RQD index, the necessary physical properties, the axial compressive resistance of the rock core. In some cases, it is necessary to determine the shear resistance and fracture resistance of rocks.

4.5.5 When there is one or several geological processes and phenomena of engineering dynamics (earthquake, flash flood, mud and rock flood, landslide, karst,...), in addition to solving the above problems, it is necessary to refer to the respective standards for carrying out additional investigations.

4.5.6 When background treatment solutions are expected to be applied, testing and monitoring should be carried out before as well as after treatment.

4.5.7 When designing a deep excavation, it is necessary to test and forecast the possibility of lowering the groundwater level, the degree of impact on neighboring works, and recommend solutions if necessary.

5. Technical requirements for geotechnical work

5.1. Geotechnical survey before the basic design

5.1.1 The survey results of this phase are used to justify the master plan and make plans for the next survey period.

5.1.2 During this phase, the following issues should be clarified:

- Preliminary assessment of the geological conditions of the works;

- The ability to appropriately arrange construction works;

- Types of foundations that can be used for the project.

5.1.3 The survey method is to collect, analyze and synthesize relevant documents related to the survey area. In case of necessity, additional geological measurements and engineering drawings shall be added.

5.2 Geotechnical survey in the basic design stage

5.2.1 The objective of the geotechnical survey at the basic design stage is to provide data on the stratigraphy of the stratigraphic structure, the mechanical and physical properties of the soil, rock, and groundwater as a basis for the argumentation and construction recommend suitable foundation options.

5.2.2 Survey tasks include:

- Determine the distribution of soil and rock layers by area and depth;

- Determination of physical and mechanical properties of soil layers, underground water level, and preliminary assessment of water corrosion ability;

- Preliminary assessment of load-bearing capacity, the compressibility of the studied rock layers;

- Preliminary assessment of adverse geological phenomena affecting the construction of deep excavation pits and recommendations for support options.

5.2.3 Survey method:

- Geophysical methods;

- Drilling combined with SPT experiment, taking soil samples for characterization and stratification. The mass of undisturbed samples for laboratory testing was taken from several representative boreholes: 1 sample to 2 samples for soil layers with a thickness of less than 5 m, 2 samples to 3 samples for soil layers with a thickness of 5 m to 10 m. m, 3 samples to 4 samples for soil thickness from 10 m to 15 m;

- Static penetration tests are alternated between boreholes, to determine the general variation of the thickness of the soil layers and their hardness;

- Field shear test (for soil with state from soft plastic to flowing);

- Laboratory testing with undamaged soil samples to determine soil classification criteria,  strength and deformation properties of soils;

- Chemical analysis of some typical water samples.

5.2.4 Arrangement of exploration network

5.2.4.1 During the survey phase for basic design, the exploration points are arranged according to the network, the distance between the survey points is decided based on the following factors:

- the adequacy and quality of the documents collected during the initial investigation phase;

- The importance and complexity of the structure, load, and layout area of ​​the work;

- Complexity of geological conditions of the works.

NOTE: It is recommended to refer to the table of the complexity level of geological conditions works (Appendix 2 TCVN 4419:1987).

5.2.4.2. The distance between survey points usually ranges from 50 m to 200 m. However, the specific arrangement of the survey points still varies depending on the distribution characteristics of each zone in the construction site. It is possible to arrange a shear test, horizontal compression test, penetration test between boreholes with thicker spacing depending on technical requirements.

5.2.5 The depth of exploration points is determined depending on the work, the importance of the structure, the complexity of the geological conditions of the works (refer to Appendix C).

5.3 Geotechnical survey at the engineering design stage

- Drilling combined with SPT experiment, taking soil samples for characterization and stratification. The mass of undisturbed samples for laboratory testing was taken from several representative boreholes: 1 sample to 2 samples for soil layers with a thickness of less than 5 m, 2 samples to 3 samples for soil layers with a thickness of 5 m to 10 m. m, 3 samples to 4 samples for soil thickness from 10 m to 15 m;

- Static penetration tests are alternated between boreholes, to determine the general variation of the thickness of the soil layers and their hardness;

- Field shearing test (for soil with state from soft plastic to flowing);

- Laboratory testing with undamaged soil samples to determine soil classification criteria, durability, and deformation of soil types;

- Chemical analysis of some typical water samples.

5.2.4 Arrangement of exploration network

5.2.4.1 During the survey phase for basic design, the exploration points are arranged according to the network, the distance between the survey points is decided based on the following factors:

- the adequacy and quality of the documents collected during the initial investigation phase;

- The importance and complexity of the structure, load, and layout area of ​​the work;

- Complexity of geological conditions of the works.

NOTE: It is recommended to refer to the table of the complexity level of engineering geological conditions (Appendix 2 TCVN 4419: 1987).

5.2.4.2. The distance between survey points usually ranges from 50 m to 200 m. However, the specific arrangement of the survey points still varies depending on the distribution characteristics of each zone in the construction site. It is possible to arrange a shear test, horizontal compression test, penetration test between boreholes with thicker spacing depending on technical requirements.

5.2.5 The depth of exploration points is determined depending on the work, the importance of the structure, the complexity of the geological conditions of the works (refer to Appendix C).

5.3 Geotechnical survey at the engineering design stage

5.3.1 The purpose of the geotechnical survey at the engineering design stage is to provide complete and detailed data on the geological structure, physical and mechanical parameters of soil, rock, and groundwater of the construction site to correct the construction location of the work items and calculate the foundation design of the work.

5.3.2 The survey task is to clarify the geological conditions of the works; Detailed division of soil and rock layers; hydrogeological characteristics and geological phenomena unfavorable for the construction of works; Take groundwater samples to determine physical properties, analyze the chemical composition and assess corrosion potential for concrete and reinforced concrete structures.

5.3.3 Geotechnical survey for deep excavation design and construction:

- Clarifying the distribution and thickness of soil layers within the influence of excavation pit construction, the mechanical criteria of the ground need to meet the design calculation model;

- Clarifying the current status, structural characteristics, and deformation ability for adjacent works and underground works due to excavation pit construction. In the area with densely concentrated pipelines, it is necessary to collect data records to clarify the type, layout, depth and, when necessary, conduct exploration of the pipeline system under the construction;

- Provide hydrogeological parameters and conditions for the calculation of anti-retention and waterproofing for the wall and bottom of the excavation pit.

5.3.4 Survey for foundation reinforcement plan (if any):

- Provide the necessary physical and mechanical parameters of the ground for the design and construction work; reinforcement treatment plan;

- Assess the possibility of impact of the reinforcement treatment plan on the environment and neighboring works. Recommend corresponding treatment options.

5.3.5 Method of the exploratory survey in the technical design stage:

- Drilling in combination with SPT experiments, taking samples for testing. Take soil samples to determine the physical and mechanical parameters. The number of test samples for each soil layer must be sufficient to gather statistics and ensure the required reliability specified in construction standards.

- Static penetration test to provide data for pile foundation design;

- Dynamic penetration test is combined to correct the pile-like layer roof and select the pile driving method;

- Trimming test is mainly used with soft soil (mud, peat, soil with state from soft to flowing);

- Monitoring underground water to determine the static water level change mode, measuring water pressure in depth;

- Testing to determine the permeability coefficient of soil and rock at the site;

- Laboratory testing of undisturbed and intact soil and rock samples were taken from boreholes and exploratory excavations, refer to Appendix F. In addition to testing all physical and mechanical parameters, it is necessary to determine the characteristics. Characterization of water permeability, expansion, and contraction of soil and rock in basements. Analysis and evaluation of the degree of corrosion of concrete and reinforced concrete structures of underground water.

5.3.6 Survey network arrangement

5.3.6.1 Exploration network must be arranged directly at the foundation of blocks, works, or work items. The distance between the exploration points depends on the complexity of the geological conditions of the construction, the grade of the building, the size of the house, and the sensitivity to uneven settlement of the ground (refer to Appendix D)...

5.3.6.2 The composition and volume of survey work for the design of the friction pile foundation can be found in Table D.1 Appendix D.

5.3.6.3 The number of controlled survey points should not be less than 1/3 of the number of survey points.

5.3.6.4 The number of drilling sites for sampling and field testing is not less than 2/3 of the total number of survey sites.

5.3.7 Depth of probe points

5.3.7.1 The depth of exploration in the engineering design phase depends mainly on the survey results of the previous phase and the type of foundation used.

5.3.7.2 For works on natural foundations, the depth of exploration works depends on the depth of the compression zone but must be greater than the depth of the compression zone from 1 m to 2 m.

5.3.7.3 For piles or piles with the main bearing tip, the exploration depth is not less than 5 m below the pile tip. For the bearing layer which is rock, if it encounters debris bands due to faults or caves, it is recommended to drill into the unweathered bedrock at least 3 m.

5.3.7.4 For friction or friction piles, the exploration depth must exceed the depth of the operating zone of the conventional block foundation under the pile tip, to a depth to which the stress of the structure transmitted is less than or equal 15% of the stress is caused by the soil's own weight.

5.3.7.5 For the option of using piles of different lengths, the survey depth is determined according to the pile with the largest length.

5.3.7.6 The depth and scope of survey for the excavation pit must be based on the geological conditions of the works and design requirements to determine:

- The exploration depth should be taken from twice to three times the depth of the excavation pit. In this range, if the hard clay layer, gravel, or rock layer is encountered, the depth can be reduced based on the requirements of the reinforcement technique. survey;

- The survey site should be wider than the excavation, from two to three times the depth of the excavation;

- In the area with a thick soft soil layer, the survey scope and depth should be expanded appropriately. In addition to the excavation area, it is necessary to investigate, research and collect documents to supplement.

5.4 Geotechnical survey at the stage of construction drawing design - survey for construction

5.4.1 Geotechnical investigation of this stage is conducted before or during the construction of the works. The purpose of this survey phase is to check and correct the issues that are doubtful, lacking, or supplementing the contingency plan mentioned in the conclusions and recommendations at the end of the design phase to move to the next phase. construction section.

5.4.2 Survey tasks include:

- Supplementing or correcting some information on stratigraphy, geological structure, physical and mechanical criteria of soil and underground water in case of necessity to confirm or adjust the construction plan;

- Experiment to check results during and after construction such as static compression of piles, ultrasound, drilling to check pile cores, installation of equipment, and settlement monitoring... If there is a plan for the treatment of foundation reinforcement, it is necessary to conduct an experiment Field test to control, check the design parameters and effectiveness of the reinforcement plan.

5.4.3 Network layout and exploration depth are decided depending on specific requirements and conditions.

6. Geotechnical monitoring

6.1 Geotechnical monitoring aims to monitor the deformation and durability changes of soil and rock as well as of construction during construction and exploitation. The location and time of monitoring are determined depending on the characteristics of the construction works and the geotechnical conditions of the construction area.

6.2 Geotechnical monitoring must reflect the scale and value of phenomena in space and time, detect the development trend of adverse phenomena to plan effective prevention measures.

6.3 For high-rise buildings, the main monitoring objects are houses and deep excavation pits.

6.4 For houses, monitoring is mainly settlement, inclination, cracking, and damage. Monitoring equipment, monitoring methods, and measurement standards need to conform to the requirements of TCVN 9364:2012.

6.5 For deep excavation pits, geotechnical monitoring mainly serves the construction, including:

- Subsidence of the soil surface around the excavation pit;

- Transverse displacement into excavation pit;

- Groundwater level or hydro pressure level;

- Exploding the bottom of the dug hole;

- Displacement of the top of the pile wall;

- Earth pressure acting on the pile wall;

- Displacement and stress in the struts of the support system;

- Deformation of houses and neighboring structures.

6.6 In case the works are built next to the old ones, it is necessary to carry out experiments and monitoring for the neighboring works to take timely remedial measures, including the following:

- Observe the status of neighboring foundations, foundation types, and foundation conditions. An open excavation can be carried out to observe the shape, condition, and size of the adjacent foundation;

- Observing the current state of the body of the building, existing cracks, and damage to propose necessary preventive measures during the construction process;

- Set settlement datum and inclinometer at neighboring works to monitor continuously during foundation construction.

7. Geotechnical survey report

The report of geotechnical survey results is a summary of the results of the geotechnical investigation at the site and in the room at the construction site, referring to the geotechnical documents in the vicinity. Contents of the Geotechnical Survey Report see Appendix A

Appendix A

(Regulations)

Contents of the geotechnical survey report

A.1 Opening

- State the purpose and requirements of the survey;

- Bases for survey work;

- Overview of site conditions, structural characteristics, loads, number of floors, and other special requirements.

A.2 Survey plan

- The volume and progress of survey and experimental work;

- Arrange exploration points;

- Survey methods: specify the standard or basis applied to carry out a survey and experimental methods.

A.3 Geotechnical conditions of the ground

- Distinguish, divide and describe soil and rock in stratigraphic order, including the distribution area and position through survey results;

- Groundwater and problems related to construction and corrosion, cavitation to foundation materials and works;

- Synthesize physical and mechanical properties of soil and rock layers according to types of experiments and select representative values ​​for foundation design calculations;

- Geotechnical monitoring results (if any).

A.4 Assessment of geotechnical conditions for construction work

- Clearly present stratigraphy, physical and mechanical properties of the ground, qualitatively and quantitatively assess the uniformity of the soil layers, and characterize the strength and deformation of the ground;

- Indicate the adverse geological phenomena that are or may be present, analyze the stability of the ground under the effect of loads;

- Assess the influence of hydrogeological conditions on the foundation construction, evaluate the stability of the slope, the corrosion of water to concrete and reinforced concrete, and propose a plan. preventive;

- There should be analysis and recommendations on the rational use of the geological environment for construction;

- Assess the impact of construction works with neighboring works.

A.5 General conclusions and recommendations

A.6 Appendix

The report appendix includes maps, sections, drawings, spreadsheets, charts. Required appendices include:

- The layout of the exploration points;

- The stratigraphic pillars of the borehole;

- Geotechnical section: longitudinal and transverse sections on which the order of layer names, layer numbers, symbols of soil, rock, underground water, experimental diagrams, and representative physical and mechanical values ​​are shown. ..;

- Summary table of mechanical and mechanical properties by class;

- Experimental charts in the field and the room;

- Other tables related to survey results;

- References.

Appendix B

(Refer)

Some concepts and definitions of high-rise buildings

B.1 Definition of the tall building according to the International Commission on Tall Buildings:

A house whose height is a determining factor in design, construction, or use conditions that are different from ordinary houses is called a high-rise building.

B.2 Based on the height and number of floors, the International Committee of Tall Buildings divides tall buildings into 4 types as follows:

- High-rise buildings of class 1: from 9 floors to 16 floors (50 m high);

- High-rise buildings of type 2: from 17 floors to 25 floors (the highest is 75 m);

- High-rise buildings of class 3: from 26 floors to 40 floors (100 m high);

- High-rise buildings of class 4: with 40 floors or more (called super high-rise buildings).

B.3 Regarding the starting height of high-rise buildings, different countries have different regulations. Based on fire prevention requirements, the starting height of high-rise buildings is presented in Table.

B.1.

Table B.1 – Starting heights of tall buildings in some countries

Country name

Starting altitude

China

House with 10 floors and 10 floors or more, other architecture 28 m

The former Soviet Union)

Houses with 10 floors and 10 floors or more, other architectures over 7 floors

America

22m to 25m or more than 7 floors

France

Housing > 50m, other structures > 28m

Brother

24.3m

Japan

11 floors, 31m

West Germany

≥ 22m (from floor level)

Belgium

25m (from the ground outside the house)

 

Appendix

(Refer)

Depth of exploration points – Survey phase for basic design

C.1 For complex geological conditions, important works, large to very large scale

- If there is soft soil: must drill through soft soil, 1/2 of the drilling points must be at least 3 m into good soil (N > 30);

- If good soil is encountered: drill to a depth of 10 m to 15 m;

- If encountering shallow rock: drill into fresh rock 1 m;

- Each item (or each unit) drills 1 control hole.

C.2 For medium geological conditions, the construction is quite important and the scale is quite large

- If there is soft soil: must drill through soft soil, 1/3 of the drilling points into good soil at least 3 m

(NSPT > 30);

- If good soil is encountered: drill up to 10 m deep;

- If encountering shallow rock: drill into fresh rock 1 m;

- Each item (or each unit) drills 1 control hole.

C.3 For simple geological conditions, works of normal type, quite large scale

- If good soil is encountered: drill to a depth of 5 m to 10 m;

- If encountering shallow rock: drill touches un-weathered rock;

- One control hole for the whole area.

EASY Appendix

(Refer)

Exploration network layout – Survey phase for engineering design

D.1 For complex geological conditions, important works, sensitive to settlement and deflection:

- Normal drilling distance from 20 m to 30 m; It is possible to add penetration with an average distance of 10 m;

- Requires no less than three survey points for a single house and no less than three to five points for a cluster of houses or structures;

- In special cases where it is necessary to delineate the distribution of soft soil layers, the distribution of sliding blocks and karsts, etc., the spacing may be less than 20 m.

NOTE When the geological condition of the ground is complicated, or the design has special requirements, it is possible to arrange a suitable thickening gap.

D.2 For medium geological conditions, the structure is quite important, quite sensitive to irregular settlement:

- Normal drilling distance from 30 m to 50 m; can add penetration with an average distance of 15 m to 25 m;

- Requires no less than three survey points for a single house and no less than 3 to 5 points for a cluster of houses or structures.

NOTE When the geological condition of the ground is complicated, or the design has special requirements, it is possible to arrange a suitable thickening gap.

D.3 For simple geological conditions, normal type works:

- Normal drilling distance from 50 m to 75 m; It is possible to add penetration with an average distance of 25 m to 30 m;

- No less than three survey points are required for a single house or a cluster of houses or structures.

NOTE When the geological condition of the ground is complicated, or the design has special requirements, it is possible to arrange a suitable thickening gap.

Table D.1 – Composition and volume of geotechnical survey work

Features of the house and design works

The composition of the geotechnical investigation depends on the characteristics of the house and the design work

The volume of geotechnical investigation depends on

complexity and geological conditions of the works

Level I

Level II

Level III

first

2

3

4

5

Houses under 9 floors, including the load of the wall transmitted to the foundation, is not more than 50 T/m or the load transmitted to the column frame is not more than 300 T when mass construction.

1. Drill

According to the 70 m x 70 m grid, each house (work) must have at least 1 borehole.

According to the 50 m x 50 m grid, each house (work) must have at least 2 drill holes.

According to the grid of 30 m x 30 m, each house (work) must have at least 3 boreholes.

 

2. In-room soil test

In an engineering geology unit, each criterion must have at least 6 values ​​giá

 

 

 

3. Piercing Static

According to the grid, 35 m x 35 m but each house (building) must have at least 2 points.

According to the grid, 25 m x 25 m but each house (building) must have at least 3 points.

According to the grid, 15 m x 15 m but each house (building) must have at least 5 points.

 

4. Standard pile test

Within a geotechnical engineering unit at each specific depth, there must be at least 3 experimental sites

 

 

Housing under 16 floors, including the load of the wall transmitted to the foundation, is not more than 300T/m or the load transmitted to the column frame is not more than 2000T.

1. Drill

According to the 50 m x 50 m grid, each house (work) must have at least 2 drill holes.

According to the 40 m x 40 m grid, each house (work) must have at least 3 drill holes.

According to the 30 m x 30 m grid, each house (work) must have at least 4 boreholes.

 

2. In-room soil test

In a single

geological resources

works, each indicator must have at least 6 values

 

 

 

3. Piercing Static

According to the grid, 25 m x 25 m but each house (building) must have at least 5 points.

According to the grid, 20 m x 20 m but each house (building) must have at least 7 points.

According to the grid, 15 m x 15 m but each house (building) must have at least 10 points.

 

4. Horizontal compression test

Within an engineering geology unit, there must be at least 6 experiments thí

 

 

 

5. Standard pile test

Within an engineering geology unit at each specific depth, there must be at least 3 standard pile tests and 1 field pile test.

 

 

 

6. Field test of piles

 

 

Houses and constructions are too high (houses 16 to 28 floors, warehouses, chimneys, furnaces), industrial buildings with loads transmitted to the frame columns greater than 2 000 T.

1. Drill

According to the 40 m x 40 m grid, each house (work) must have at least 3 drill holes.

According to the 30 m x 30 m grid, each house (work) must have at least 4 boreholes.

According to the 20 m x 20 m grid, each house (work) must have at least 5 drill holes.

 

2. Experiment in the room

In an engineering geology unit, each criterion must have at least 6 values ​​giá

 

 

 

3. Piercing Static

According to the grid, 20 m x 20 m but each house (building) must have at least 6 points.

According to the grid, 15 m x 15 m but each house (building) must have at least 8 points.

According to the grid, 10 m x 10 m but each house (building) must have at least 10 points.

 

4. Horizontal compression test

Within an engineering geology unit, there must be at least 6 experiments thí

 

 

 

5. Static load test

Within a geoengineering unit, there must be at least 2 tests at each specific depth, but the values ​​obtained should not differ by more than 30 % of the value.

 

 

 

6. Field test of piles

Within a geoengineering unit, there must be at least 2 tests at each specific depth, but the values ​​obtained should not differ by more than 30 % of the value.

 

 

Appendix E

(Refer)

Field test methods

E.1 Static penetration test can be performed to clarify stratigraphic uniformity, deformation, and load-carrying properties of the ground, to estimate the bearing capacity of a single pile... The test is performed in layers of cohesive and loose soil that do not contain gravel. The purpose of this experiment is to provide additional information for the design and construction of underground sections with small depths.

E.2 Standard penetration test SPT  is a dynamic penetration test performed in a borehole, which is used as a basis for dividing rock layers, determining the density of sandy soils, the state of clay soils, determine the position of the soil layer to place the pile tip, calculate the bearing capacity of the pile, as well as design the shallow foundation... This test is also used to determine the stopping depth of the survey, evaluate the liquefaction ability of the pile. sandy soils saturated with water.

E.3 Wing shear test is performed in soil layers with plastic to flowing state, in the borehole to determine the undrained shear resistance of the soil, providing additional information for design and construction. construction of underground works of not great depth.

E.4 The borehole horizontal compression test is used for loose and cohesive soil layers and can be performed at different depths to determine deformation properties and transverse deformation modulus of rock.

E.5 Water pressure test in the borehole is used to determine the water permeability, water absorption capacity of cracked bedrock. The essence of the experimental method is to isolate each drill hole with specialized buttons, then force water into the isolated rock sections with predetermined pressure regimes.

E.6 Test for water absorption from borehole  to determine flow rate, permeability coefficient, including soil in foundation pit wall, hydraulic slope and ability to generate hydrodynamic pressure, serving the work anti-retaining and waterproofing design for the wall and bottom of the foundation pit, design and construction work to lower the groundwater level

E.7 Water monitoring to determine the groundwater level variation in the survey area. The soil water regime is measured by two types of experiments:

E.7.1 Static water level measurement (standpipe): the depth of the pipe is less than 15 m to provide information about the surface water regime. The water gauge allows for infiltration over the entire length. The measurement results are used for the design and construction of excavation pits, basement walls, and proposed methods of drying the foundation bottom for construction.

E.7.2 Measuring water pressure according to depth (piezometer tube):  the depth of the measuring head depends on stratigraphic structure and aquifer location. The measurement results are used for the design and construction of bored piles, walls in the ground, construction solutions according to wet technology (select appropriate construction technology).

E.8 Test to determine soil resistance: carried out in the borehole according to depth to provide design parameters for lightning protection and grounding.

E.9 In some cases, it is necessary to identify strata or pockets of gas in the soil that can cause poisoning or explosion when drilling bored piles or digging deep foundation pits.

E.10 When surveying for technical design and making construction drawings of pile foundations conduct static compression tests to determine the load capacity of single piles and other methods to check the quality of trees. pile. The mass and specifications must comply with the relevant current standards.

Appendix F

(Refer)

Laboratory test methods

F.1 Laboratory test methods need to be selected and implemented to provide all necessary information by the design and calculation models that have been set out in the geotechnical survey task.

F.2 Experiment to determine physical criteria for soil identification and classification.

F.3 Determination of deformation criteria  (through compression test without hip expansion),  strength criteria  (through three-axis compression test, one-axis compression test, or direct shear test. continued). The methods and diagrams of compression and shear testing should be selected depending on the actual working conditions of the work, the calculation model of the underground part of the building.

F.4 The test to determine the strength criteria of the foundation soil  should be by the following regulations:

F.4.1 The selection of shear test method and diagram should be based on the calculation method, construction speed, and drainage conditions of the ground to determine and match the actual bearing condition of the building. . For works with relatively fast construction speed, poorly drained soil can use rapid shear test without consolidation, no drainage.

For works with slow construction speed, well-drained soil can use the undrained consolidation shear test but should take into account the degree of consolidation of the foundation soil due to the construction load and the pre-action consolidation load.

F.4.2 For calculation of slope stability and design of retaining walls, anchoring in the ground... should use undrained, unconsolidated triaxial compression test or hip expansion compression test, flat shear test fast no drainage.

F.4.3 When it is necessary to use strength criteria to calculate the bearing capacity of piles, laboratory tests must comply with the following regulations:

F.4.3.1 When it is necessary to calculate the ultimate friction along the pile body, the values ​​of Cu, φ u  of the unconsolidated, undrained test in the triaxial compression test can be used.

F.4.3.2 When it is necessary to calculate the extreme resistance below the pile tip, for clay soils the Cu , φ u values of the undrained consolidation test or the C', φ' values ​​of the test can be used. drainage consolidation in the triaxial compression test.

F.5 Consolidation compression test is used to determine the deformation of the ground, the degree of consolidation, to assess the possibility of negative friction force. For excavation work, to monitor elastic deformation, compression and unloading tests should be carried out at each level according to the actual working conditions of the works.

F.6 For rock samples, it is recommended to determine the uniaxial compressive strength of the rock in a dry and saturated state. In some necessary cases, it is possible to further determine the petrographic composition and mineralization of the rock.

F.7 Water samples need to be tested to assess the properties and degree of corrosion of water for foundation concrete structures.

 

TCVN 9363:2012 - SURVEY FOR CONSTRUCTION - GEOTECHNICAL SURVEY FOR BUILDINGS

 

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