|
With the rapid economic development Because of our country’s urban high-rise buildings, subway project; a large number of municipal projects and increasing the scale of underground space development, which generated a lot of deep excavation. As large amount of deep excavation works, construction of high cost, therefore; deep excavation has become an important part of controlling progress, quality and the economy, and thus the structure of deep foundation pit optimal design become more and more important. Deep Foundation Pit Excavation and support design has many factors, such as engineering geological conditions, hydrogeological conditions, site conditions, construction management, site monitoring, and closely related to the surrounding buildings, and thus more difficult as well.PARS structure is applied and developed a new type of anti-slide structure in 80, the 20th century, which is most commonly used form of supporting structure of a foundation in our country. PARS deep foundation design research involves many structure of multi-discipline, which need to integratet to use of technology of the pile, bolt technology, engineering, construction technology and monitoring techniques and other aspects of knowledge, involving a wide range, is subject of a comprehensive which is more difficult.Based on the research of designing and application on structure of pile and supporting in the deep foundation, this paper analyzes the advantages and disadvantages that exist in the design process. Structure in the upper part of PARS, using cutting slope and soil nailing combined support in the form, which can guarantee the stability of foundation, but also reduce the cost of the project cost. Because of pile with advance supporting role, it which be able to control excavation of soil deformation pit early in the process, so that the foundation stability has been improved. As piles embedded depth is large, and the higher the pile stiffness and strength, so that the boundary constraints have been strengthened, which would weaken the plastic deformation within the soil. Meanwhile, the use of prestressed cable, so that to effectively control displacement of the supporting piles are horizontal and vertical, thus control stability of the foundation better. Researched the influence law of the inclination and anchorage depth of the anchor on the maximum horizontal displacement of the supporting structure, that the anchor in 0-30°angle between the changes, the maximum horizontal displacement of less; the anchorage depth should be set based on specific project circumstances, this foundation used the depth of 1.6m.Finally, ANSYS finite element software was used to simulate foundation excavation process and analyze increase trend of gradually increasing of the supporting pile and the stress with the rising of foundation depth. Because prestress is exerted to the anchor stress generating the stress concentration, making relatively large internal stress in the between the pile and anchor. Boundary conditions in the soil under the constraints, the overall level of displacement is small, the maximum displacement occurred in the excavation pit at the bottom in the vertical direction, that is rebound phenomenon the when common excavation, Matching the actual situation.The other parameters remain unchanged, the pile embedded depth from the 6m into 5m, respectively using F-SPW software and ANSYS software to simulate, and the results obtained is compared to the result when the pile embedded depth is 6m. The analysis shows that little change in the internal force and displacement of the pile anchor foundation when the two cases on embedded depth, can meet the specifications. The resulting, the design program is conservative in embedded depth of the pile, which can be further optimized.
|