GBJ 112-1987 Technical specification for construction in expansive soil areas
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Engineering Construction Standard Full-text Information System
National Standard of the People's Republic of China
Technical Specifications for Buildings in Expansive Soil Areas
GBJ112—87
1989Beijing
Engineering Construction Standard Full-text Information System
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National Standard of the People's Republic of China
Technical Specifications for Buildings in Expansive Soil Areas
GBJ112—87
Editor Department: Ministry of Urban and Rural Construction and Environmental Protection of the People's Republic of China Standard department: State Planning Commission of the People's Republic of China Effective date: August 1, 1988
Engineering Construction Standards Full Text Information System
Engineering Construction Standards Full Text Information System
Notice on the release of the "Technical Specifications for Buildings in Expansive Soil Areas"
Ji Biao [1987] No. 2110
According to the requirements of the former State Construction Commission (78) Jianfa She Zi No. 562, the "Technical Specifications for Buildings in Expansive Soil Areas" jointly compiled by the Ministry of Urban and Rural Construction and Environmental Protection and relevant departments has been reviewed by relevant departments. The "Technical Specifications for Buildings in Expansive Soil Areas" GBJ112-87 is now approved as a national standard and will be implemented on August 1, 1988. This standard is managed by the Ministry of Urban and Rural Construction and Environmental Protection, and its specific interpretation and other work are the responsibility of the China Academy of Building Research of the Ministry of Urban and Rural Construction and Environmental Protection. The publication and distribution is the responsibility of China Planning Press.
National Planning Commission
November 12, 1987
Engineering Construction Standards Full Text Information System
Engineering Construction Standards Full Text Information System
Preparation Instructions
This specification is prepared by the China Academy of Building Research of our Ministry in conjunction with relevant survey and design units across the country in accordance with the notice of the former State Construction Commission (78) Jianfashezi No. 562.
On the basis of summarizing the existing engineering construction practice experience and scientific research results in expansive soil areas, the specification preparation team further conducted in-depth investigations and studies and put forward a draft specification for soliciting opinions. Opinions were widely solicited nationwide, and after several rounds of discussions and revisions, it was finally reviewed and finalized by our Ministry in conjunction with relevant departments.
This specification is divided into five chapters: general provisions, survey, design, construction and maintenance management, and is accompanied by six appendices, including indoor tests of engineering characteristics of expansive soils. This specification is compiled for the first time. All units are requested to summarize experience and accumulate data during implementation. Any problems and revision opinions encountered should be sent to the Institute of Foundation Engineering of China Academy of Building Research (Xiaohuangzhuang, Anwai, Beijing) at any time for reference in future revisions. Ministry of Urban and Rural Construction and Environmental Protection
October 9, 1987
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Main Symbols
A—Area of pile tip
Horizontal distance from the outer edge of the foundation to the shoulder
b——Width of the bottom surface of the foundation
d——Depth of foundation placement
d. Depth of atmospheric influence
l—Standard value of foundation bearing capacity
【f.】—Design value of friction between the pile side and the soil f,—Design value of bearing capacity per unit area of the pile tip G. Self-weight of cap and soil
h——Designed slope height
ho——Original height of soil sample
hw——Height of soil sample after immersion and expansion and stabilization-Length of pile anchored in non-expansive soil layer
p——Pressure acting on foundation
P.——Soil expansion force
Q—Vertical load acting on the top of single pile
Q-Vertical load acting on the top surface of pile cap s—Swelling and contraction deformation of foundation soil
s——Graded deformation of foundation soil
-Swelling deformation of foundation soil
s——Contraction deformation of foundation soil
"-Pile body circumference
.-Expansion shear force of soil on the side of pile in the layer with sharp atmospheric influence%-Original volume of soil sample
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——Volume of soil sample after expansion and stabilization in water w——Natural water content of soil
3——Plastic limit water content of soil
%——Calculation depth
Insertion——Shrinkage coefficient of foundation soil
8u——Free expansion rate of soil
8%—Swelling rate of soil under a certain pressure8——Linear shrinkage rate of soil
——Empirical coefficient for calculating expansion and contraction deformation. —Empirical coefficient for calculating expansion deformationEmpirical coefficient for calculating contraction deformation
Humidity coefficient of soil
Engineering Construction Standard Full Text Information System
Engineering Construction Standard Full Text Information System
Chapter 1 General
Chapter 2 Survey
Section 1
Section 2
Section 3||t t||Chapter 3
Section 1
Section 2
Section 3
Section 4
Section 5
Section 6
Section 7
Section 8
Chapter 4
Section 1
Section 2
Section 3
Chapter 5
Appendix 2
Appendix 3
Appendix 4
Appendix 5
Appendix 6
General provisions
Engineering property indicators of soil
Site and foundation evaluation
General provisions
Foundation calculation
General plan design
Foundation burial depth
Foundation treatment·
Architecture and structure·
General provisions·
Foundation and base construction
Building (structure) construction
Maintenance and management
Engineering properties of expansive soilsIndoor test
Evaporation power and precipitation in some areas of ChinaKey points of field immersion load test
Strict ground structure for use
Observation method of building deformation
Explanation of terms used in this code
Additional explanation
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Chapter 1 General
Article 1.0.1 This code is formulated to make engineering construction in expansive soil areas technologically advanced, economically reasonable, and to ensure the safety and normal use of buildings. Article 1.0.2 This code applies to the survey, design, construction and maintenance management of industrial and civil buildings in expansive soil areas. Article 1.0.3 Expansive soil should be a clay soil in which the clay component is mainly composed of hydrophilic minerals and has two deformation characteristics: significant water absorption expansion and water loss shrinkage.
Article 1.0.4 Engineering construction in expansive soil areas must be based on the characteristics of expansive soil and engineering requirements, taking into account factors such as climate characteristics, topographic conditions, and changes in soil moisture, and take appropriate measures to control local conditions. Article 1.0.5 In addition to complying with this code, engineering construction in expansive soil areas should also comply with the requirements of relevant national standards and specifications currently in force. Engineering Construction Standard Full Text Information System
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Chapter II Investigation
Section I General Provisions
Article 2.1.1 The engineering geological investigation stage should be compatible with the design stage and can be divided into three stages: site selection investigation, preliminary investigation and detailed investigation. For areas with small site area, simple geological conditions or construction experience, the investigation stage can be simplified, but it should meet the requirements of the detailed investigation stage. For areas with complex terrain and geological conditions or groups of buildings that are damaged, special investigation work should be carried out when necessary. Article 2.1.2 Site selection investigation should be based on engineering geological surveys, supplemented by a small number of exploration pits or necessary drilling work, to understand the distribution of strata, take appropriate disturbed soil samples, measure the free expansion rate, preliminarily determine whether there is expansion soil in the site, and make an engineering geological evaluation of the stability and suitability of the proposed site. Article 2.1.3 Engineering geological surveys should include the following: 1. Preliminary investigation of the geological age, causes and expansion and contraction properties of expansive soils; 2. Divide geomorphic units to understand the topographical morphology; 3. Find out whether there are shallow landslides, ground fissures, gullies and hidden karst and other adverse geological phenomena in the site;
4. Investigate the surface water discharge and accumulation, groundwater types, multi-year water levels and change ranges;
5. Collect local meteorological data for many years (including precipitation, evaporation, drought duration, air temperature and ground temperature, etc.) to understand its changing characteristics; 6. Investigate local construction experience and analyze the causes of building damage. Article 2.1.4. During the preliminary investigation, the expansion and contraction of expansive soil should be determined, the stability of the site and the engineering geological conditions should be evaluated, and engineering geological data should be provided to determine the general layout of the building, the foundation plan of the main buildings, and the prevention and control plan for adverse geological phenomena. Its main work should include the following contents: 1. When the engineering geological conditions are complex and the existing data do not meet the requirements, engineering geological mapping should be carried out, and the scale used can be 1/1000~1/5000; 2. Find out the causes, distribution range and degree of harm of adverse geological phenomena in the site, and estimate the seasonal variation of groundwater level and its impact on foundation soil; 3. Take original soil samples for indoor basic physical property tests, shrinkage tests, expansion force tests and expansion rate tests under 50kPa pressure to preliminarily find out the physical and mechanical properties of the expansive soil in the site.
Article 2.1.5 During the detailed investigation stage, the foundation soil layers and their physical and mechanical properties of each building should be identified in detail, and their expansion and contraction grades should be determined to provide detailed engineering geological data for foundation design, foundation treatment, slope protection and treatment of poor geological areas. Article 2.1.6 In addition to being carried out in accordance with the relevant provisions of the current national geotechnical engineering investigation specifications, field exploration and testing work should also meet the following requirements: 1. Soil sampling points should be arranged according to the building type, geomorphic unit and foundation soil expansion and contraction grade, and their number should not be less than 1/2 of the total number of exploration points. During the detailed investigation stage, there should be no less than 3 soil sampling points under each major building. 2. To take undisturbed soil samples, start from 1m below the surface and take one sample per meter from 1m to the atmospheric influence depth; additional soil samples should be taken where there are obvious changes in the soil layer; below the atmospheric influence depth, the sampling interval can be appropriately increased. 3. For important construction sites or those with special requirements, on-site water immersion load tests shall be carried out when necessary to further determine the expansion performance and bearing capacity of the foundation soil. Section 2 Engineering Properties of Soil
Article 2.2.1 The engineering properties of expansive soil shall comply with the following provisions: 1. Free expansion rate (8)
The ratio of the volume increased in water to the original volume of artificially prepared dried soil is calculated as follows:
(2.2.1-1)
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%—Original volume of soil sample (ml).
2. Expansion rate (8p)
Under a certain pressure, after the immersion expansion stabilizes, the ratio of the increased height of the sample to the original height is calculated as follows:
_hw-ho
(2.2.1-2)
Wherein, hw is the height of the soil sample after the immersion expansion stabilizes (mm); h is the original height of the soil sample (mm).
3. Shrinkage coefficient (>)
The vertical shrinkage rate of the original soil sample when the water content decreases by 1% during the linear shrinkage stage is calculated as follows:
(2.2.1-3)
Wherein, △8 is the difference in vertical shrinkage rate corresponding to the difference in water content at two points during the shrinkage process (%);
△w is the difference in water content at two points during the linear change stage of the shrinkage process (%). 4. Expansion force (P.)
The maximum internal stress generated by the expansion of the original soil sample due to water immersion when the volume remains unchanged. The test of the above-mentioned characteristic index shall be carried out in accordance with the provisions of Appendix 1 of this code. Section 3 Site and foundation evaluation
Article 2.3.1 When evaluating the site of expansive soil, the distribution of the main expansion forces and the topographic conditions in the construction site shall be found out, and a comprehensive evaluation shall be made based on the engineering geological characteristics and the free expansion rate of the king and other indicators. If necessary, the mineral composition identification and other tests of the soil shall be carried out.
Article 2.3.2 Sites with the following engineering geological characteristics and soils with a free expansion rate greater than or equal to 40% shall be judged as expansive soils: Engineering Construction Standard Full Text Information System
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1. Developed cracks, often with smooth surfaces and scratches, and some cracks are filled with gray-white or gray-green clay. It is hard or hard plastic under natural conditions; 2. It is mostly exposed in the second or higher terraces, piedmont and basin edge hilly areas, with gentle terrain and no obvious natural steep slopes; 3. Shallow plastic landslides and ground fissures are common, and the walls of newly excavated pits (trench) are prone to collapse;
4. Cracks in buildings open and close with climate change. Article 2.3.3 The expansion potential of expansive soil can be divided into three categories according to Table 2.3.3: Expansion potential classification of expansive soil
Free expansion rate (%)
40≤<65
Expansion potential
Article 2.3.4 According to the terrain and geomorphic conditions, the construction site can be divided into the following two categories: 1. Flat site: the terrain slope is less than 5; the terrain slope is greater than 5° and less than 14°, and the slope top area with a horizontal distance of more than 10m from the slope shoulder. 2. Sloping site: The terrain slope is greater than or equal to 5°. Although the terrain slope is less than 5°, the local terrain height difference within the same building is greater than 1m. Article 2.3.5 The evaluation of the expansion soil foundation should be carried out according to the degree of influence of the expansion and contraction deformation of the foundation on the low-rise brick-concrete house. The expansion and contraction level of the foundation can be divided into three levels according to Table 2.3.5.
Engineering Construction Standard Full Text Information System
WArticle 1 When evaluating the site of expansive soil, the distribution of the main expansive soils and the topographic conditions in the construction site should be found out, and a comprehensive evaluation should be conducted based on the engineering geological characteristics and the free expansion rate of the soil. If necessary, the mineral composition identification and other tests of the soil should be carried out.
Article 2.3.2 Sites with the following engineering geological characteristics and soils with a free expansion rate greater than or equal to 40% should be determined as expansive soils: Engineering Construction Standard Full Text Information System
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1. Developed cracks, often with smooth surfaces and scratches, some cracks are filled with gray-white and gray-green clay. Under natural conditions, it is hard or hard plastic; 2. It is mostly exposed in the second or higher terraces, piedmont and hilly areas on the edge of the basin, with gentle terrain and no obvious natural steep slopes; 3. Shallow plastic landslides and ground fissures are common, and the walls of newly excavated pits (trench) are prone to collapse;
4. Cracks in buildings open and close with climate change. Article 2.3.3 The expansion potential of expansive soil can be divided into three categories according to Table 2.3.3: Expansive soil expansion potential classification
Free expansion rate (%)
40≤<65
Expansion potential
Article 2.3.4 According to the terrain and geomorphic conditions, the construction site can be divided into the following two categories: 1. Flat site: the terrain slope is less than 5; the terrain slope is greater than 5° and less than 14°, and the slope top area with a horizontal distance of more than 10m from the slope shoulder. 2. Sloping site: the terrain slope is greater than or equal to 5°. Although the terrain slope is less than 5°, the local terrain height difference within the same building is greater than 1m. Article 2.3.5 The evaluation of the expansive soil foundation should be carried out according to the degree of influence of the expansion and contraction deformation of the foundation on the low-rise brick-concrete house. The expansion and contraction level of the foundation can be divided into three levels according to Table 2.3.5.
Engineering Construction Standard Full-text Information System
WArticle 1 When evaluating the site of expansive soil, the distribution of the main expansive soils and the topographic conditions in the construction site should be found out, and a comprehensive evaluation should be conducted based on the engineering geological characteristics and the free expansion rate of the soil. If necessary, the mineral composition identification and other tests of the soil should be carried out.
Article 2.3.2 Sites with the following engineering geological characteristics and soils with a free expansion rate greater than or equal to 40% should be determined as expansive soils: Engineering Construction Standard Full Text Information System
W.bzsoso.coI Engineering Construction Standard Full Text Information System
1. Developed cracks, often with smooth surfaces and scratches, some cracks are filled with gray-white and gray-green clay. Under natural conditions, it is hard or hard plastic; 2. It is mostly exposed in the second or higher terraces, piedmont and hilly areas on the edge of the basin, with gentle terrain and no obvious natural steep slopes; 3. Shallow plastic landslides and ground fissures are common, and the walls of newly excavated pits (trench) are prone to collapse;
4. Cracks in buildings open and close with climate change. Article 2.3.3 The expansion potential of expansive soil can be divided into three categories according to Table 2.3.3: Expansive soil expansion potential classification
Free expansion rate (%)bZxz.net
40≤<65
Expansion potential
Article 2.3.4 According to the terrain and geomorphic conditions, the construction site can be divided into the following two categories: 1. Flat site: the terrain slope is less than 5; the terrain slope is greater than 5° and less than 14°, and the slope top area with a horizontal distance of more than 10m from the slope shoulder. 2. Sloping site: the terrain slope is greater than or equal to 5°. Although the terrain slope is less than 5°, the local terrain height difference within the same building is greater than 1m. Article 2.3.5 The evaluation of the expansive soil foundation should be carried out according to the degree of influence of the expansion and contraction deformation of the foundation on the low-rise brick-concrete house. The expansion and contraction level of the foundation can be divided into three levels according to Table 2.3.5.
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