Recently, Hunan Wangwang Hospital Medical Building Expansion Project (Phase II), the first case of rock stratum "first capping, then bottom" reverse construction project in China, was successfully completed. The project is undertaken by the general contracting company of Hunan Construction Engineering Group, and the overall construction adopts the full top-down construction technology, which is the project with the largest excavation depth, the largest excavation volume (over 300000 cubic meters) and the largest bottom excavation depth of the full top-down method in the country.
Hunan Wangwang Hospital Medical Building Expansion Project (Phase II)
"First Top, Then Bottom" Full Reverse Method Project Introduction
Four Difficulties "Forcing Out" Full Reverse Method
Wangwang Hospital is the first Taiwanese-funded private hospital in Hunan, and the original hospital scale has been difficult to meet the demand. To this end, the second phase of the expansion project has been launched, with a total construction area of about 170000 square meters, including 77.3 meters (20 floors) above ground and 30.7 meters (7 floors) underground. The hospital requires that the open building concept, integration concept, urban infrastructure sharing concept, new and old building function integration and green environmental protection concept be integrated into the project to maximize the social and economic value of the project. After repeated demonstration and research by the hospital and Hunan Construction Group, the final plan is determined that the exterior wall of the basement of the project is adjacent to the red line construction, and the second is to build a seven-storey basement. To create conditions for the later connection with the urban rail transit line.
As the project is located in one of the core sections of the main urban area of Changsha City, the downtown area is bustling and the traffic flow is dense. In the specific construction, there are four main difficulties:
the surrounding environment is complex
. As the construction site is located in the central urban area of Changsha City, the floating population is large, and the traffic flow in the surrounding sections is large. The foundation pit of the second phase project is very close to the first phase building, municipal roads and subway sections, and the construction is difficult. The excavation depth of the foundation pit of the
project is 32 meters, which is easily affected by groundwater, rainfall and construction dynamic load, so the drainage of the site is particularly important. The
construction site is narrow
. The outer wall of the basement of the project is not far from the boundary line of the construction land. The construction must be carried out within the boundary line. The narrow construction site makes the specific construction more difficult.
Pollutant control Yan
Wangwang Hospital is a hospital project located in the downtown area of the city. In order to ensure the safety and sanitation of the project environment, the project has strict requirements on the treatment and control of construction pollutants such as dust, light, vibration and wastewater.
Due to these construction difficulties, if the traditional construction method is adopted, although the process is simple, there are a series of problems such as large excavation area, high risk of foundation pit deformation, significant impact on surrounding buildings, and poor environmental protection of construction, which are not applicable to the construction requirements of this project. What to do?
In order to solve the above problems, Hunan Construction Engineering Group has organized experts to demonstrate for many times, and adopted various means to analyze and study from different angles, and finally adopted the "first capping, then bottom" top-down construction method, which has been unanimously praised by Party a, design, supervision, industry authorities and other parties.
"Top first and bottom later" full reverse construction technology
Full reverse construction
technology Drilling and grooving construction
of underground continuous wall in soft rock "One column and one pile" steel pipe column, The key design technology of "first capping, then bottom" reverse construction
method of lattice column precision guidance has developed the key technology of collaborative design of "two walls in one" diaphragm wall, pile-column joint bearing vertical support system, beam and slab horizontal support system, and the external technology of medical pipeline. It significantly reduces the impact of pipeline maintenance on the daily operation of the hospital.
At the same time, the upper structure and basement of the project building can be constructed in parallel and three-dimensional, which can effectively shorten the construction period, and the upper main structure can be capped earlier than bottom of the foundation slab, so that the main structure can carry out water, heating, electricity, decoration and other work in advance.
The use of "two walls in one" diaphragm wall not only eliminates the need to set up a separate enclosure wall, but also maximizes the basement area within the scope of the project land and increases the effective use area.
In addition, by adopting the technology, the deformation of the foundation pit can be effectively controlled, the stability of the foundation pit can be improved, the influence on the surrounding buildings in the construction process can be minimized, the construction cost can be saved, and the carbon emission can be effectively reduced. At the same time, the excavation of foundation pit is not affected by rainfall and other weather factors, and the construction noise, dust, vibration, light pollution and other aspects will be greatly reduced or reduced compared with the traditional construction method, and the environmental benefits are very significant.
Under the condition of full reverse construction method, the project has successfully achieved the construction goal of "capping first, then bottom", and the feedback of site implementation effect is good up to the bottom of foundation slab. Five doctors from the National Post-doctoral Workstation of Hunan Construction Engineering Group have also carried out post-doctoral research relying on the project, which has been successfully approved by the Natural Science Foundation of Hunan Province. So far, two national invention patents and seven utility model patents have been obtained. In addition, the total economic benefit of about 30 million yuan has been created after the construction of full reverse construction method.
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