Title of Engineering Geology Thesis: On Engineering Geological Exploration
Engineering geological survey is to complete the application of engineering geology in economic construction. Disaster prevention? The concrete practice process of this general task is to provide reliable geological basis for the planning, design and construction of engineering construction as a whole, so as to make full use of favorable natural and geological conditions, avoid or transform unfavorable geological factors and ensure the safety and normal use of buildings. This paper mainly analyzes the related problems of geological investigation of building engineering.
Keywords: construction engineering geological exploration quality
China Library Classification Number: TU76 1 Document Identification Number: A Document Number:
I. Introduction
Engineering geology has become an independent discipline as early as 265438+1930s, and the recent research results are so profound that nonlinear science is used to study its complexity. The geological conditions are complex and changeable, and vary from region to region and site. In the foundation design of various buildings, to ensure their safety, two technical conditions must be met at the same time: ① the foundation strength condition, that is, to ensure the stability of the foundation without shear failure or sliding failure; ② The deformation conditions of foundation, namely settlement, differential settlement, inclination and local inclination, should not exceed the allowable deformation value of foundation. Geological survey report is an important basis for building engineering design and necessary information to ensure that the above two technical conditions are met. Scientific geological survey report can not only improve the quality of architectural design, but also save engineering quantity and reduce investment, thus bringing greater economic benefits.
In recent years, China's engineering geological exploration has made great progress and become the right hand of China's geological engineering construction. Geological survey is to investigate and understand the geological conditions such as rocks, strata, structures, hydrology and landforms in the relevant areas of geological engineering, and provide necessary basis and parameters for the planning, design and construction of engineering construction. The contents of geological exploration report will determine different investment and construction management schemes, and different construction schemes will determine different engineering quality.
Second, the problems existing in engineering geological investigation
For the foundation of important buildings with complex geological conditions or special construction requirements, sometimes it is necessary to carry out construction survey when the situation can not be completely ascertained or all the required information can not be obtained through detailed survey. At present, there are some problems in civil engineering geological survey, mainly in the following aspects:
1, lack of understanding of the importance and value of engineering geological investigation.
Geological survey mainly includes two aspects, one is to reveal the geological composition, the other is to provide the mechanical index of soil; The geological composition determines the choice of foundation treatment scheme, and the mechanical index has great influence on the project cost. As we all know, the underground is invisible and intangible. Only through drilling survey, the construction site is unique and the survey results are not comparable. Therefore, it is very important for the construction unit to choose a survey unit with strong professional skills, strict operation specifications and accurate results, which is of great significance to the safety of buildings, the smooth progress of engineering construction and the saving of investment.
2. The quality of geological prospecting reports of geological prospecting departments is not high.
The quality of geological prospecting reports put forward by geological prospecting departments is not high, and there are many mistakes. At present, the contents of some geological exploration reports are simplified as not providing geotechnical test indexes, not making evaluation, not making clear conclusions, and not putting forward engineering treatment suggestions. In some reports, what should be omitted is not omitted, and what should not be omitted is not omitted; The drawings that should not be attached are attached, and there is no prescribed format; Not much to say, but it's all nonsense. Its practice is to deceive unprofessional managers and cater to some designers by providing foundation bearing capacity indicators.
3. The exploration method is wrong.
Some exploration departments use the so-called static load test to determine the bearing capacity of the soil layers on both sides of the fracturing pit, which is misleading and unscientific. Imagine that the pressure required for the rupture of shallow and deep soil layers on both sides is different, so which pressure setting is used as the foundation bearing capacity. In addition, the soil layers on both sides of fracturing can not replace or explain that the pressure value is the bearing capacity of vertical soil layer foundation.
4. Lack of supervision of engineering geological survey.
First, the engineering geological survey is carried out in the early stage of the project, and the construction unit independently chooses the survey unit. General construction units lack professional knowledge in this field and have insufficient understanding of the importance of geological survey. Therefore, the requirements for the investigation unit are not high, and a result is enough. Considering more drilling costs, the requirements for technology are lighter. Second, geological exploration is field work, geotechnical test and data collation. The whole process is completed by the exploration unit alone without supervision. How many holes have been drilled, how deep, how many soil samples have been taken and how many geotechnical tests have been made? There are loopholes. Are they from the exploration team? Conscience? Live. Now the construction drawing review also reviews the geological prospecting results, which is afterwards. As long as the data is made passable, it can pass, the geological composition is seriously inconsistent with the actual construction, and the accuracy of mechanical indicators is even more difficult to distinguish.
Third, the countermeasures of engineering geological exploration work
1, and establish the specifications and system of engineering geological exploration.
Before the formal exploration, the engineering geological exploration engineer should understand and master the requirements of the construction unit for geotechnical engineering investigation, as well as the structural form, purpose and load of the project in charge, formulate the investigation norms and systems according to the construction site conditions, formulate a scientific and reasonable time plan according to the actual situation, reasonably arrange indoor data collation, geotechnical test and site construction, stipulate the technical requirements such as sampling test, in-situ test and drilling construction, and clarify the norms and systems in the investigation process.
2. Refine exploration data and improve the quality of geological exploration report.
After the geological exploration is completed and the exploration data are obtained, the exploration data should be sorted, analyzed and refined according to the characteristics of the project itself and the surrounding environment, so as to ensure the scientificity of soil layer division and the accuracy of measurement data, and communicate with designers to explain the parameters with great differences, so that designers can better grasp the relevant situation.
3. Choose appropriate investigation and testing methods.
Exploration methods mainly include drilling, sampling and testing, all of which are highly targeted. Choosing a suitable exploration method can get twice the result with half the effort, otherwise it will not only fail to play its due role, but also waste a lot of working time and money. To choose an economical, reasonable and feasible engineering investigation method, we should first know the existing geological data of the site and the structures along the line in detail, fully communicate with the engineering construction designers, and make clear the engineering geological problems that need to be solved, and then carry out the investigation, especially the investigation of unknown areas, and complete the investigation in stages and several times. According to different materials and geological structures, the methods used are: dry core drilling, mud wall protection rotary drilling and so on.
4. Supervise the exploration site.
Before construction, engineering geological surveyors shall conduct investigation and verification on the construction site in combination with various reports provided by the owner; Check the size and length of the drill pipe used in the drilling rig to ensure that the technical parameters of each part meet the requirements of survey and construction; All in-situ test items in geotechnical engineering investigation shall meet the requirements of Code for Geotechnical Engineering Investigation and other relevant codes and regulations; Reasonable drilling method should be selected. When drilling into a rock stratum, the drilling speed should be reasonably determined according to the strength of the rock stratum. When drilling in silt, sandy soil and soft soil strata below the groundwater level, the mud wall protection drilling method should be adopted and the drilling speed should be strictly limited. Do a good job in sampling management When sampling, the size of drill pipe should be strictly controlled, and undisturbed soil samples should not be taken for core cutting pipe. Samples taken shall be labeled in time and kept properly. For the measurement of elevation and water level, the elevation of the Yellow Sea should be selected first. If conditions do not permit, the assumed elevation shall be adopted. It is best to bury the reference point in a place that is not easy to be damaged, and measure the groundwater level uniformly after the project construction. The engineer shall inspect and accept the field data in time to ensure that the number of in-situ tests and the number of samples taken from the main bearing stratum meet the requirements. At the same time, they should also pay attention to controlling the ups and downs of the bearing stratum, and conduct small-scale drilling for possible abnormal points to find out the specific situation.
5. Control the engineering geological survey period.
As an important factor of engineering geological survey project, the survey period must meet the planned requirements. When compiling the survey outline, the time for field work, geotechnical test and indoor data collation should be arranged as a whole according to the engineering situation, survey workload and survey methods, site topography and geological conditions. Establish the concept of project life cycle cost and effectively control the project cost. Survey and design should consider the whole process of planning, construction, maintenance and operation, apply the concept of project life cycle cost, compare and select technical schemes, reasonably determine the functional grade of the project, realize the organic combination of technology and economy, and ensure the quality of survey and design work. The design stage is the most critical stage of project life cycle cost control. We should look at the cost from the whole process of the whole life cycle of the project, and pay attention to the control of construction cost, maintenance cost and maintenance cost, as well as the control of environmental cost and social cost. Using scientific methods to evaluate the design scheme reasonably, on the premise of ensuring safety and function, the best technical and economic benefits can be achieved by improving technical content and using design indicators reasonably and flexibly.
Concluding remarks
The survey results are mainly reflected in the engineering geological survey report, and the excellent survey report will undoubtedly provide reliable engineering geological basis for the design. On the contrary, the unqualified report will bring serious adverse consequences to the design, and even cause quality accidents. Therefore, it is necessary to have a clear positioning of the survey work, attach importance to the engineering geological survey, and implement management and standardization. Only in this way can we ensure that we have more reliable survey results.
refer to
[1] Huang Guangqiong. Discussion on engineering geological survey and foundation treatment measures of high-rise buildings [J]. Modern commerce and trade .2011(02)
[2] dollars. Analysis on Geological Survey of Building Engineering [J]. Commodities and Quality 2009(S6)
[3] Tamia Liu. Several problems that should be paid attention to in geological investigation of civil engineering [J]. Science and Technology Information.2009 (16)
The second part of the title of the paper is the discussion of engineering geological investigation.
This paper introduces the purpose of engineering geological survey and the factors that determine the survey task, and illustrates the process of engineering geological survey in detail, including preparatory work, survey contents in each stage and engineering geological survey report, with a view to guide relevant personnel to carry out engineering geological survey correctly and provide accurate geological data for design and construction.
Key words: engineering geological survey; Purpose; Task; investigation report
Buildings are built above the ground, and the distribution of soil layers below the ground, the looseness and strength of soil and the depth of groundwater will all affect the safety of buildings under construction. Therefore, in order to ensure the accuracy of building and its foundation design, it is necessary to have the geological data of the building site as a scientific basis. Only when we have a comprehensive understanding and accurate grasp of the geological data of the construction site can we better design the building and its foundation.
First, the purpose of engineering geological investigation
The main purpose of engineering geological exploration is to investigate and analyze the site of the project under construction by means of pit depth, penetration test and drilling, so as to provide the required geological data for engineering design and construction.
Second, the factors that determine the investigation task
(A) the complexity of the construction site
According to the topography of the building site, the complexity of the site is divided into three levels: simple site, which has little influence on the building foundation; Medium site, which may have a certain impact on the building foundation; The complex site has a great influence on the foundation of the building.
(2) Study the geological conditions where the project is located and the local construction experience.
For example, in a strange area, the lack of research on local geological conditions will increase the exploration workload; On the contrary, if you have experience in engineering construction here, the time and workload will be reduced.
Three. Construction scale and building grade
According to the type of the project, the load of the building foundation and the degree of the overall consequences caused by the damage of the building foundation, the building can be divided into three grades. First-class buildings mainly refer to key or memorable buildings, and the damage consequences are very serious. Secondary buildings mainly refer to buildings with large foundation load and serious damage consequences. The three types of buildings mainly refer to the building foundation with less load and no serious damage consequences.
Preparation of survey work. 1) Accept the engineering geological exploration task book, and formulate the corresponding exploration work plan in combination with the geological conditions of the engineering site; 2) For sites with large building scale or complicated geological conditions, engineering geological mapping should be carried out to observe the geological conditions of the site on the spot; 3) Set exploration points and exploration lines, find out the geological conditions of the site and obtain geological samples by various geological exploration means or methods; 4) Carry out physical strength test and water quality analysis test on the obtained geological samples.
Four, the contents of each stage of geological exploration
(1) site selection survey
1.
Site selection exploration refers to evaluating the geological stability and suitability of engineering sites.
2. Survey work in site selection stage
1) Collect information such as topography, earthquake, mineral resources, engineering geological information, climate, natural conditions and so on in the area where the project is located; 2) Conduct field investigation on the engineering site to get a preliminary understanding of the soil structure, formation reasons, approximate molding age, main soil layers and groundwater level of the site. 3) Understand the scale, structure and geological data of buildings in the nearby area; 4) The geological conditions of the project site are complex, and the existing data can't accurately reflect the geological information, so necessary geological mapping and exploration work are needed.
(2) Preliminary investigation?
1.
1) to evaluate the foundation stability of the building under construction; 2) Provide necessary information for the general layout of the building; 3) Provide reference materials for the foundation construction of the main building of this project; 4) In case of adverse geological phenomena, submit a prevention plan.
2. Main tasks
1) Preliminary understanding of site geology. 2) Understand the groundwater level and freezing depth; 3) Find out the unknown geological phenomena, scope, impact on the project and development trend in the site.
(3) Detailed exploration
1.
1) Evaluate the building foundation from the perspective of engineering geology and put forward corresponding suggestions; 2) Provide detailed geological engineering data for building foundation design; 3) Provide engineering data support for the reinforcement and treatment of building foundation; 4) Provide geological data for the prevention and control of adverse geological conditions.
On intellectuals
2. Main tasks
1) The main means of detailed investigation are in-situ testing, exploration and indoor sample testing. 2) For complex sites or Class I and II buildings, detailed exploration points shall be arranged according to main column lines; Other sites and buildings can be arranged along the periphery of buildings or buildings; Important equipment foundation should be arranged separately. 3) The depth of exploration hole should be based on the principle of main bearing stratum of foundation. If it is necessary to check whether the foundation is deformed, some exploration holes can be compressed with subbase. 4) During the detailed exploration of the site, the geological samples extracted from the in-situ test wells and exploration holes shall be determined according to the geological complexity and the scale or category of buildings. The location of sampling and in-situ testing shall be determined according to the design requirements and foundation conditions.
(4) Construction survey
1) Complex foundations of important buildings need to be inspected. When inspecting the pipe trench, the geological sketch of the pipe trench should be made, the stratum boundary should be measured, and the distribution and uniformity of artificial fill should be found out. Supplementary exploration and testing should be carried out when necessary. 2) After foundation pit excavation, the geological conditions are inconsistent with the original survey data, which may affect the engineering quality. 3) During the design and construction of deep foundation pit, relevant foundation monitoring work should be carried out. 4) When the foundation is treated and reinforced, it needs to be designed and tested. 5) Karst caves or soil caves in the foundation are well developed and need further identification and treatment. 6) Slope instability occurs during construction, which needs to be observed and treated.
Verb (abbreviation of verb) engineering geological survey report
(A) the body part
1) exploration tasks and general situation; 2) Whether it affects the instability of building foundation and its influence degree; 3) Geological soil layer structure, strength and physical and mechanical properties of each soil layer in the project site; 4) The depth of low water level, the change of water quality and the degree of corrosion to building materials; 5) Dividing the site type and site category of the seismic fortification area, and distinguishing saturated sand and silt; 6) Analyze the foundation scheme of the building foundation, and put forward the economic and feasible design scheme, especially the suggestion of testing the places that need to be paid attention to in the foundation design and construction; 7) When required by the project, technical parameters required for slope stability calculation and supporting design of deep foundation pit excavation shall be provided, and its influence on surrounding existing buildings and underground facilities shall be demonstrated; Suggestions on technical parameters and methods of dewatering in foundation pit construction: provide design water level for calculating groundwater buoyancy.
(2) Chart part
1) layout of exploration points; ? 2) Engineering geological profile, comprehensive engineering geological map or engineering geological zoning map; ? 3) Summary of physical and mechanical tests of soil. According to the needs of major projects, draw a comprehensive engineering geological map or geological zoning map, geological histogram or comprehensive geological histogram and related test curves.
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