Foundation pit support and construction of Luneng Real Estate S-20 commercial building

Transcription

1 Smart Construction Research RESEARCH ARTICLE Foundation pit support and construction of Luneng Real Estate S-20 commercial building Song Xueli, Xu Xiudong, Wang Lange, Yang Huajun Beijing Construction Engineering 4 Construction Engineering Co., Ltd. Pomegranate Village Project Department Abstract: With the gradual improvement of urban construction, urban construction land increasingly tense, the lack of land caused by the formation of expensive land premium. Alterations and new construction is basically plug-in embedded, the original underground, the building on the protection of the building is also increasingly diverse and complex, the construction is also increasing the difficulty. The safe use of existing facilities and the safety of construction are problems that must be addressed in urban construction. Keywords: foundation; pit support; Construction Introduction Citation: Song XL, et al.(2017). Foundation pit support and construction of Luneng Real Estate S-20 commercial building, vol. 1: doi: /scr. v Copyright: 2017 Song Xueli, Xu Xiudong, Wang Lange, Yang Huajun. This is an Open Access article distributed under the terms of the Creative Com mons Attribution-Non Commercial 4.0 Inter national License ( creativecommons.org/licenses/ by-nc/4.0/), permit ting all noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited. With the gradual improvement of urban construction, urban construction land increasingly tense, the lack of land caused by the formation of expensive land premium. Alterations and new construction is basically plug-in embedded, the original underground, the building on the protection of the building is also increasingly diverse and complex, the construction is also increasing the difficulty. The safe use of existing facilities and the safety of construction are problems that must be addressed in urban construction. I plant the construction of the Luneng real estate development of the pomegranate Zhuang Road S-20 commercial space project, located in Fengtai District of Beijing town and the town of Pomegranate Zhuang Road intersection on the north side of the south side of the Metro Line 10. The project covers an area of square meters, the ground floor of the four eight floors, cornice height of 80 meters, with a total construction area of square meters, of which square meters on the ground, underground square meters, frame shear wall structure. Foundation excavation depth of meters local depth of meters. S-20 south of the subway is subway tunnel 10, the most dangerous southeast corner of the slope from the slope of the nearest pile only 2.075m, subway tunnel base from the proposed building base 7.37 meters. Foundation excavation after the subway hanging tunnel floating on the edge of the foundation pit, and it s buried in a lot of municipal pipeline. 10 subway tunnel for the tunnel, tunnel radius of about 6 meters, the tunnel buried depth of about 4.2 meters. The MTR Corporation has put forward high requirements for the safe operation and protection of the MTRC: monitoring the displacement and the subway tunnel during the construction of the foundation pit to the completion of the building. The the tunnel, the the track structure of the deformation control value between the [-3 ~ 1.5mm], the tunnel structure settlement control value [-3 ~ 1.5mm], tunnel lateral deformation [2.5mm] convergence [2mm] And the requirements of the construction of the pit to the completion of the floor during the completion of the train every night after the the deformation to monitor the structure of the completion of the completion of the tank to 3 days after the backfill monitoring; positive and negative zero above the construction of a monitoring layer; After monitoring every 3 months. Smart Construction Research 2017, Volume 1 12

2 Song Xueli, et al. Metro Line 10 is a very important line in Beijing, transport is very busy, social impact, to ensure the safe operation of the subway Is the construction process and the delivery of buildings must be guaranteed after the primary conditions. 1 The foundation pit slope protection Due to the relatively deep foundation pit of the proposed building, the subway tunnel is relatively close to the building. The design unit adopts the parallel double row piles on the foundation pit slope protection. The center distance of the two rows of slope protection pile is 4000mm, the diameter is 1700, between the pile design of the connection anchor, the foundation pit wall with a water curtain of curtain diameter 500. In the upper two rows of piles of subway tunnels, three rows of connecting rods are designed with a diameter of 700, length L = 5300 mm and a connecting rod inclination of 10. Two rows of connecting rods are designed between the two rows of piles, L = 7500, the upper connecting rod angle of 25, under the connecting rod angle of 22. The two rows of piles at the top of the design of the grid plate will be two rows of piles into a whole. In the tunnel under the 1.8m to do three rows of prestressed anchor length L = 15.2m, As the southeast side of the foundation pit slope from the subway tunnel is only meters, the department can only design a row of slope protection pile. After the construction of the slope protection pile, the concrete should be excavated after the design strength is reached. The excavation of the earth excavation takes the connecting rod and the prestressed tension, and the cement slurry can reach the next step. Foundation excavation and earth excavation of the foundation pit to take a subsection excavation, sub-section do anchor. So that two rows of piles to form a retaining wall. The program was approved by experts and approved by the MTR Corporation. 2 The level of support to increase the pit After the construction of the slope protection pile, the total package unit to the building line, found that the slope of the slope from the basement wall only 100mm ~ 200mm space, not taking into account the prestressed anchor steel beam (2I28 I-beam) on the underground buildings Wall waterproof layer thickness. The basement wall waterproof layer must be attached to the side wall of the slope protection pile, and the steel beam used to anchor the prestressed anchor rod must be removed to ensure the crosssectional dimensions of the basement facade and the waterproof construction practices. If the steel beam prestressed anchor will be removed, the retaining wall will become a high cantilever retaining wall, slope protection pile may occur lateral displacement deformation, subway tunnel lateral control value does not exceed -3 ~ 1.5mm which will be difficult to guarantee. To this end after repeated demonstration, the original slope protection program to modify the supplement. It is required to reinforce the slope protection pile before removing the steel beam. As the slope from the subway tunnel is not the same distance, the depth of the pit is not the same, to take the reinforcement roof is not consistent. As follows: Smart Construction Research 2017, Volume 1 13

3 Foundation pit support and construction of Luneng Real Estate S-20 commercial building In the second district (3-6 axis, located in the sixth construction section, the construction section is divided by the general contractor according to the construction requirements of the eighth paragraph.) The same basis, the foundation depth, excavation depth of 17.25m, but from the subway tunnel is further, just remove the bottom of the basement wall size of the impact of the bottom of a steel beam, the bolt pull to diagonal support. The support points on the slope support pile are located 500 points above the ground floor structure board. In order to make the slope of the pile force evenly, in the slope of the pile to add a concrete legs. One end of the oblique support is supported on the cow and the other end is supported on the base plate, and the support is supported every 3 meters. In the underground four-story structure of concrete pouring completed to achieve the design strength, and then remove the oblique support. Its principle is: in the underground four-story structure of the external walls of concrete pouring, the underground structure and slope protection pile has been formed in its strength and removal of oblique support, the underground four-story structure weight and stiffness instead of prestressed anchor support slope pile laterally. Displacement, to ensure the stability of slope protection pile. Above the part of the steel beam removed with the completion of the underground structure and then gradually removed. As the three districts (6-16 axis, located in the sixth and seventh construction section) pit excavation depth of 17.25m, closer to the subway tunnel, the section to support the length of the longest range, in the upper part of the use of horizontal support The lower part of the use of oblique support. Horizontal support requirements to support the proposed building, the support point is located in the ground floor of the second floor beam, the second support in the base floor with inclined support. The support spacing is set to a maximum of 3.48 m and a minimum of m. The forth sections (19-22 axis, eighth construction section) are located in the southeast corner of the nearest subway tunnel, but the basement is only two layers (the section is only two floors from the subway), the excavation depth is 8.85 meters. The slope of the slope of the above-mentioned two horizontal support, support spacing of 3 meters, respectively, supported in the slope of the pile beam and the ground floor of the two roof beam 500 above. Set up above 4, the following set 4 road. Second and third levels of horizontal support span of about 18 meters. Four levels of horizontal support span of about 6 meters. 3 The basement of the construction methods Basement construction order to take the first construction does not affect the subway tunnel part of the construction to the four-story structure, and then construction near the subway side of the underground structure, to facilitate the protection of slope support. On the subway side of the basement according to its distance from the tunnel to take away from the far and near the way construction. For the construction of the basement structure to take a sub-section, the second area from the tunnel ahead of the basic floor of the basic construction, in order to carry out reinforcement support; three, Smart Construction Research 2017, Volume 1 14

4 Song Xueli, et al. four sections from the tunnel closer to the more dangerous location to take a certain set aside Safe distance, earth first excavation, to be underground construction to meet the support conditions to take side of the excavation side of the construction measures. The main consideration is that the gravity of the earth is guaranteed by the slope stability control of the section of the subway tunnel deformation. As the original building structure is divided into two parts of the construction, construction staggered for a long time, consider the building will result in uneven settlement. In order to ensure the safety and free settlement of the structure, the designer has added a post-settling zone to the construction site. After pouring the pouring time by settlement observation on both sides of the building tends to be consistent, you can start pouring. In the second and third district underground four-story structure of concrete pouring to achieve the design strength, in order to gradually remove the following support bar, removal of the support according to the dynamic the tunnel to remove the situation. The monitoring of the data results, when the subway tunnel and track deformation control within the allowable range, and then the above structure of the construction. Forth areas in the ground floor after construction, and then remove the level of support. Second and third districts due to the need to dismantle the anchor steel beam. In order to improve the effect of changing, to meet the slope of the overall force and the slope requirements in the support point to increase a horizontal beam. In order to facilitate connection with the support rod and force, the beam used to push the way back. At the fulcrum set the plane buried -16mmX900X900 steel plate pressure surface, so that the pressure surface uniform force and the top of the ramp support. In the bottom plate and horizontal beam concrete strength reaches 70% of the design strength, you can install the support bar; in the floor and the beam strength of concrete to reach the design strength, and then remove the anchor steel beam. Support rod with φ609x14 stereotypes steel pipe, installed in place after the correction with the jack to impose a force of 300KN, bar top tightened with a steel wedge tightening adjustable fixed end. In the position of the center of gravity under the center of the bracing bar, the brackets are brazed to prevent the bending of the diagonal bar. When the concrete is poured, the concrete will be poured into the structure, and the concrete will reach the strength in the basement structure and then cut to remove the support. Second and third districts in the completion of the four-story basement roof construction, concrete design strength, to remove the oblique support. At this point, the lateral pressure of the slope protection pile is transmitted to the underground structure, thus ensuring the stability of the slope protection pile. Demolition of the support and the concrete beam when the use of sub-cutting, subsection of the way, in the demolition of the lower floor and steel to do the appropriate protection to prevent pollution and smashing. After the bottom of the three sections of the brackets removed, the upper level of support to continue to retain the structure to the ground after the second floor of the roof, in order to remove the above level support. Four sections due to the distance from the tunnel near the slope of the pile cannot be used prestressed anchor, excavation after the slope of the horizontal part of the horizontal stiffness by increasing the level of support to ensure that the focus is reinforced fortification area. In the surface of the earth digging 1.5 to 2 meters after the first to do the CFG pile, (first do CFG pile construction, is to avoid the installation of horizontal support, CFG pile construction difficulties). And then in the slope of the pile at the beam to do the first level of support, after reinforcement to continue under the earth excavation, in the ground floor of the roof beam 500mm to do the second level of support. Support to follow-up construction. Smart Construction Research 2017, Volume 1 15

5 Foundation pit support and construction of Luneng Real Estate S-20 commercial building In order to ensure uniform the slope protection pile in the support position set steel purlin, steel purlin is a kind of lattice structure steel beam. The gap between the steel purlin and the slope protection pile is tightly packed with concrete to ensure uniform force of the slope protection pile. Horizontal support rod and oblique support are used φ609x14 steel pipe, steel pipe for the standard section, each connected by the flange connection plate bolts connected. In the bar after lifting in place to adjust the fixed, with the jack to impose a horizontal force of 300KN will be adjustable after the adjustment of the active side of the use of steel wedge ready to dry welding. The main structure of the fourth district to the construction of the second steel within the mouth of the mouth under the standard elevation of 500mm and concrete to achieve the design strength, the removal of the second horizontal steel support, the upper structure of the construction; structural construction to the first steel within the mouth Elevation 500mm and the concrete to achieve the design strength, the removal of the first level of steel within the support, the above structure construction. As the support rod structure construction pouring in the structure, the demolition of the use of gas cutting removed, leaving the hole with 5mm thick steel plate along the surrounding welding plugging, steel outside the brush anti-rust paint, the inner hole with no shrinkage high strength grouting material for watering plug, Elimination of excess concrete with cement mortar and structural wall smoothing. 4 Slope protection of the pile The deformation monitoring of fixed point of slope protection is the main means to test the design and construction effectiveness of slope protection pile. Deformation monitoring is also set in the slope of the slope and the subway tunnel and track. In the construction site set up pit excavation pile deformation, displacement monitoring and inspection of the point, by the professional units set up regular equipment to monitor. The displacement of the slope of the slope of the resettlement of fixedpoint fixed-point monitoring, inspection. Construction unit technical staff to monitor, inspect the data records to analyze, to ensure that the construction process of security measures in place. The contents of the manual inspection are mainly the deformation of the foundation pit support, cracks and location, quantity, width, direction, depth, development trend; foundation pit slope seepage and other conditions to check. Through the observation of the site observation data, the stability of the slope protection pile to develop the construction program, the project during the construction period by site inspection observation slope protection values are set within the range. Slope does not appear deformation, cracks, water seepage and so on. Deformation monitoring of subway tunnels and railroad tracks is carried out by professional companies. There are 42 monitoring points for the settlement of the orbital structure on the 10th line and 12 monitoring points for the transverse deformation of the track structure. The is deformed by 13 monitoring points. Orbital geometric position 25 monitoring points, seamless line rail displacement of 8 monitoring points. 10 monitoring points for the settlement of the of the 10th line, 42 monitoring points for the orbital structure subsidence, 13 monitoring points for the transverse the track, 20 monitoring points for the track geometry, 8 rails for the seamless rails To monitor. The earth excavation in the third and fourth districts of this project has been completed from 2016 on August 5 to December 25, The monitoring data are controlled within the predetermined range. After monitoring the reinforcement of the slope support, the monitoring results of the subway tunnel are as follows: Smart Construction Research 2017, Volume 1 16

6 Song Xueli, et al. Table 1. No Line 10 manual monitoring phase s and cumulative s in the maximum statistics table object structure structure Test item Vertical and deformation of deformation joint Horizontal Vertical and deformation of deformation joint Horizontal 6 level 7 gauge Seamless lines Rail displacement Measuring point number Phase maximum Cumulative maximum Rate of Control value (mm/ d) conclusions ZGD (-3 1.5) Normal YGD3-3 YGD6-3 YGD (-3 1.5) Normal YGD Normal YGD YGD ± Normal YGH Normal YGH Normal YSD (-3 1.5) Normal YSD (-3 1.5) Normal YSD Normal ZSD Normal YSH4 YSH8 YSH6 ±0.4 ± Normal YSH Normal All the points (+4-2) Normal 10-YSP6 10- YSP ZSP (+4-2) Normal All the points Normal 10-YSP ZSP4 ± Normal 10-YZ Normal 10-YZ Normal Note: the table in the settlement point + said the uplift, - that sink. + In the horizontal displacement of the measuring point that the displacement to the inside of the subway, - represents the lateral displacement to the subway. + Means that the measured value is greater than the design value, - means that the measured value is smaller than the design value. level measurement: along the train direction of the right track than the left track that +, the right track than the left track that -. Table 2. No line automation monitoring phase and cumulative maximum statistics table object Test item Vertical deformation of tunnel structure and deformation of deformation joint Measuring point number Phase maximum Cumulative maximum Rate of Control value (mm/d) conclusions 10-Y3 10-Z2 ±0.17 ±0.02 (-3,1.5) Normal 10-Y4 ± (-3,1.5) Normal 10-Z(3~4) Normal 10-Z(3~4) Normal Note: The vertical the table and the rate of +, said the uplift, - on behalf of the sink. Through the observation of the slope and slope protection of the site, the professional company s manual and automated monitoring of the subway tunnel and rail data show that the subway tunnel and track deformation values are controlled within the allowable range during the construction did not affect the safety of the subway run. During the construction of underground structure, the slope and slope of slope protection are in steady state, which shows that the reinforcement measures of slope protection pile are effective and feasible. Smart Construction Research 2017, Volume 1 17