First, the characteristics of deep foundation pit construction in civil engineering
Generally speaking, deep foundation pit construction is a complex link in civil engineering, and the quality of deep foundation pit construction plays a key role in the safety and overall quality of buildings. At present, due to the deepening of deep foundation pit construction and the increase of excavation area in recent years, the risk of deep foundation pit construction is gradually increasing. In addition, the urban underground layout is complex, which is greatly influenced by underground pipelines and surrounding buildings, and the construction of deep foundation pit is difficult. Its construction features are: 1. Construction complexity. There are many professional knowledge of foundation pit engineering design, including geotechnical engineering knowledge, structural engineering knowledge, soil mechanics theory, testing and computer technology. There is a lot of knowledge about strength, deformation and reasonable seepage in soil mechanics, such as the instability of foundation pit supporting structure caused by earth pressure in deep foundation pit, the soil destruction caused by unreasonable seepage in deep foundation pit, and the deformation of deep foundation pit after a certain period of time. Therefore, the knowledge involved in deep foundation pit is complex, which requires the construction personnel to have rich experience and professional skills; In addition, the construction of deep foundation pit is also limited by the surrounding building environment, geology and water quality conditions. If the surrounding environment of buildings is complex and underground pipelines and subways are close to the construction site of deep foundation pit, it is likely to cause certain damage or influence to the surrounding environment or objects during the excavation of deep foundation pit, making the construction of deep foundation pit more complicated. 2. Deep foundation pit construction is risky. Because the construction of deep foundation pit is influenced by various complex factors, some unsafe accidents are easy to occur during the construction process; In the preliminary work of deep foundation pit development, the exploration and design of deep foundation pit are hindered to some extent by the influence of topography, hydrology and other factors, which leads to the inaccurate design of foundation pit location and supporting structure. The construction stage is affected by weather conditions, which increases the safety hidden danger of foundation pit construction and brings great risks to deep foundation pit construction. 3. Characteristics of environmental effects. Environmental effect refers to the influence of deep foundation pit on the surrounding environment. In the process of deep foundation pit construction, it may cause the groundwater level to rise, the supporting structure of the foundation pit to be unstable, deform and move, and even have an impact on nearby buildings, underground pipelines and roads. , such as road collapse, pipeline rupture, building sinking, etc. At the same time, coupled with the earthwork transportation of deep foundation pit, these phenomena are easy to cause confusion in the surrounding environment and bring some trouble to urban traffic.
Second, the factors affecting the risk control of deep foundation pit
1. The design accuracy of foundation pit is not high. The preliminary design of deep foundation pit plays a very important role in the whole construction process. According to the investigation, some construction units have insufficient preparatory work for deep foundation pit, and the design accuracy of deep foundation pit needs to be improved. There are two main reasons for this situation: natural environment factors and human and technical equipment factors. First of all, the design of deep foundation pit is mainly influenced by the surrounding environment or natural factors, such as local topography, soil conditions, water quality, underground pipelines and surrounding buildings. When designing, it is necessary to comprehensively consider the influence of various aspects and understand the underground pipelines, water quality and soil quality, so the preparation for design is complicated and easily restricted by these factors, which brings great inconvenience to the design of deep foundation pit. In addition to these factors, the theory, method and technology of deep foundation pit construction in China are not mature, the design of deep foundation pit lacks certain basis and standards, and the technical equipment of early design is relatively backward. Some designers of deep foundation pit can't do all the work in place, so it is difficult to ensure the accuracy and precision of deep foundation pit design. 2. Many unstable factors make the construction of deep foundation pit complicated. Compared with the preparatory work of deep foundation pit, some problems are easy to occur in the construction stage of deep foundation pit, which leads to the high complexity of deep foundation pit construction. The above article also mentioned that the construction of deep foundation pit is influenced by many factors, which have certain variability, such as the groundwater level, the hardness of soil, the external pressure borne by soil, and the change of construction conditions. These changes are easily influenced by external factors, which will lead to the instability of deep foundation pit construction, and some factors will cause accidents, such as the change of soil compressive capacity will affect the supporting facilities of deep foundation pit. In addition, in the process of outsourcing, some different construction teams lack the consciousness of mutual cooperation, fail to carry out the construction according to the design scheme, and lack the ability to control and protect the site, which eventually leads to the extension of the construction period of deep foundation pit. In a word, there are many factors affecting the construction of deep foundation pit, which makes the construction process of deep foundation pit more complicated. 3. Lack of awareness and methods of risk management of deep foundation pit. Many deep foundation pit constructors lack a certain awareness of deep foundation pit risk and safety, have a superficial understanding of deep foundation pit quality during construction, fail to fully consider the influence of major factors in engineering decision-making, pay low attention to risk prevention and treatment, and fail to deal with them in time. In addition, in the preparatory process, there was no detailed review or inspection of the required building materials and plan drawings. At the same time, the inspection and maintenance of construction equipment are not in place, which leads to deep security risks and potential risks, which can not effectively ensure the smooth construction of deep foundation pit; The construction unit has not done a good job in supervising the operators, the supervision and management mechanism is not perfect, and it lacks necessary work instructions and detailed special construction plans and schemes for deep foundation pit construction. Moreover, in the process of operation, there is no guidance on standardized operation and safety for employees, and the responsibility is not clearly implemented when an accident occurs. At the same time, there is no corresponding risk assessment and prevention mechanism for the quality and safety of deep foundation pit, which has not fundamentally reduced the occurrence of construction risks. The risk management method of deep foundation pit of construction unit needs to be improved. 4. The professional level and quality of deep foundation pit workers need to be improved. Because of the complexity of deep foundation pit construction, it involves many aspects of knowledge and theory, so it requires high professional skills and experience of staff. But in reality, the professional level and skills of some deep foundation pit workers are relatively low. Due to the lack of relevant professional knowledge and practical experience, various factors, such as the adoption method and design of seepage, were not comprehensively considered in the design of deep foundation pit in the early stage, and a slight deviation would cause soil damage. In the process of construction, many people did not follow the operation requirements, some people cut corners and their own quality needs to be improved. In addition, some owners outsource the construction of deep foundation pit to different contractors. These contractors blindly pursue economic benefits, but instead reduce the construction cost of the project, such as shortening the construction period and using some low-quality materials. The low quality and level of these personnel will seriously affect the construction quality and safety of deep foundation pit and bring inconvenience to risk control and management.
Three. Dynamic management measures of risk control
According to the above research contents, it is found that the risk control management of deep foundation pit is insufficient, and the risk control of deep foundation pit should be strengthened to ensure the smooth construction and quality safety of deep foundation pit. The so-called risk control is the process of dealing with the factors that affect building construction on the basis of analysis and evaluation, and so is the risk control of deep foundation pit in this paper. On the basis of the above analysis, the methods of risk control and treatment are found, including risk avoidance, dispersion and transfer. Different construction types have different treatment methods, so it is necessary to take appropriate measures to control risks according to the actual factors and conditions of the project itself. In this paper, the risk control methods of deep foundation pit are as follows: in the preparation work, designers should make corresponding preparations, deeply investigate various factors that affect the construction of deep foundation pit, such as topography, soil quality and hydrological conditions, and make good foundation and preparation for support methods, excavation and seepage work; At the same time, we should also investigate the sensitivity of adjacent buildings, underground pipelines and adjacent roads. In addition, to do a good job in the construction design of deep foundation pit, we can first determine whether the deep foundation pit needs to be closed or closed by stages according to the surrounding traffic, commerce and other conditions, and then design the construction method, such as top-down construction or block construction. Secondly, we can understand the restrictions of location on enclosure structure and noise, and rationally design the methods used to dismantle fences and supports. Third, reasonably design the stacking of materials, the way in and out of vehicles, and earthwork transportation. Fourthly, the materials, construction methods, equipment and technology used in the design and construction process can only ensure the success of the construction in the later stage, and can effectively prevent unsafe factors in the construction and effectively control risks. 2. Risk control in the construction process. Strengthening supervision and management in the construction process plays a very important role in risk control. First of all, the construction unit should improve the supervision and management system to ensure the smooth completion of the construction. Such as employee responsibilities, construction management organization, supervision and management measures, etc. It can make employees clear their responsibilities and promote the implementation of managers' supervision and management. In the work of construction personnel, managers should strengthen the detection of employees, stop unreasonable and illegal operations in time, guide operators to operate correctly, and carry out construction in strict accordance with certain requirements. Construction units can make use of advanced information technology, timely feedback the various changes in construction and the working conditions of personnel, solve problems in time, and effectively prevent unsafe accidents. In the process of inspection, the work implementation of deep foundation pit is continuously optimized, so that risk monitoring and work optimization can be carried out simultaneously. 3. Improve the professional level and quality of employees. In order to effectively control risks, the construction unit should constantly improve the professional knowledge and skill level of operators to ensure the construction quality and safety of deep foundation pits. Units can strictly control the recruitment of personnel and select some excellent and experienced personnel; You can also regularly train internal employees and teach professional knowledge courses, so that employees can effectively improve their professional knowledge by participating in these trainings and activities; On the other hand, it is also necessary to improve the safety awareness and quality level of employees, let employees understand the importance of professional ethics, standardize operations while protecting their own safety, and reduce construction risks, thus ensuring the quality of deep foundation pits.
Four. conclusion
To sum up, the construction of deep foundation pit is a complex and critical work, which has a very important impact on the safety of buildings. Based on the analysis of the characteristics and existing problems of deep foundation pit construction, this paper puts forward the risk control methods. Construction units should attach great importance to deep foundation pit construction, adopt reasonable methods to prevent and control potential risks, ensure the safe and smooth completion of construction, and thus improve the construction quality of civil construction technology.
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