Deformation Control Technology for Reconstruction and Expansion of Newly Built Station Closely Undercrossing Long-Term Service Station
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摘要: 为保证新建车站密贴下穿服役近50年车站改扩建施工的安全稳定,开展了运营和预留车站的状态评估,依据结构状态制定了施工变形控制标准,借助数值模拟对比了不同扩建施工方案的影响,并结合现场实施验证了优选方案的效果。结果表明:先期建成车站结构存在装饰层掉落、混凝土开裂、剥落、碳化、钢筋腐蚀、底板渗漏水、区间积水及变形缝不均匀沉降等问题;交叉中隔壁法(central cross diagram,CRD)方案中预留3号线车站的最大沉降量为2.2 mm,地表沉降1.7 mm;洞桩法(pile beam arch,PBA)方案中车站的最大沉降量为1.3 mm,地表沉降1.1 mm。综合考虑多种因素后,推荐在该改扩建工程中采用PBA施工方案。现场采用PBA施工方案后,2、3号线车站结构的最大竖向变形分别为−1.28和−1.01 mm,监测指标均在安全阈值内。研究结果可为类似长期服役改扩建工程提供参考。Abstract: To ensure safety and stability of the reconstruction and expansion of the newly built station under a nearly 50 years long-term service station, the structural status of main structure and auxiliary structure of an operating station and a reserved station is inspected. The construction deformation control standard is formulated referring to the structural state. The construction impacts of different expansion construction schemes are compared by using numerical simulation. Then the effect of an optimized scheme is verified in combination with an on-site implementation. The results show that there is a series of problems in the early-built station structure, such as decoration layer falling, concrete cracking, spalling, carbonization, steel corrosion, floor leakage, interval water accumulation and uneven settlement of deformation joints. For the CRD (central cross diagram) scheme, the maximum settlement of the reserved Line 3 station is 2.2 mm, and the surface settlement is 1.7 mm. For the PBA (pile beam arch) scheme, the maximum settlement of the station is 1.3 mm, and the surface settlement is 1.1 mm. The PBA method is recommended for the reconstruction and expansion project after a comprehensive consideration of various factors. After adopting the PBA construction scheme, the maximum vertical deformations of Line 2 and Line 3 structures are −1.28 and −1.01 mm, and the monitoring indicators are within the safety thresholds. The research results can provide a reference for similar subway station reconstruction and expansion projects.
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表 1 检测项目
Table 1. Test items
Test type Detection content Method Appearance inspection Cracking, peeling, exposed reinforcement, deformation
(settlement joint), water seepage, ponding, etcSteel ruler measurement, ultrasonic detector,
hand-held strain gauge, impact echo method, etcMechanical property Strength Rebound method and coring method Durability Carbonization depth, thickness of reinforcement
protective layer, reinforcement position, chloride
ion detection, reinforcement corrosionIndicator method, electromagnetic method,
silver nitrate titration method,
half-cell point method表 2 变形控制标准(单位:mm)
Table 2. Deformation control standard (Unit:mm)
Station Vertical deformation Transverse deformation Alert value Alarm value Control value Alert value Alarm value Control value Line 2 −2.1~0.7 −2.4~0.8 −3.0~1.0 1.4 1.6 2.0 Line 3 2.8 3.2 4.0 1.4 1.6 2.0 表 3 地层参数
Table 3. Stratum parameters
Formation materials Density/
(kg·m−3)Elastic modulus/
MPaPoisson’s ratio Internal friction
angle/(°)Cohesion/kN Filling 1800 22.5 0.33 10 5 Silty clay 1950 27.0 0.30 18 27 Fine medium sand 1980 45.0 0.24 30 0 Round gravel and pebble 2150 120.0 0.22 40 0 Sandy silt 2030 110.0 0.25 28 22 表 4 结构参数
Table 4. Structure parameters
Material Density/(kg·m−3) Cohesion/kN Internal friction angle/(°) Elastic modulus/GPa Poisson’s ratio Reinforcement zone 2350 35 25 0.32 0.28 Primary support 2436 30.00 0.25 Secondary lining 2425 31.00 0.24 Pile 2425 26.00 0.20 表 5 施工方案详细对比
Table 5. Detailed comparison of construction schemes
Project Maximum settlement/mm Maximum surface settlement/mm Minimum principal stress/MPa CRD scheme 2.8 1.7 −9.43 PBA scheme 1.3 1.1 −9.08 Project Differential settlement of
deformation joint/mmWorking space Engineering cost CRD scheme 0.8 Moderate Lower PBA scheme 0.2 Less Higher 表 6 现场监测结果
Table 6. Site monitoring results
Station Vertical deformation of
structure/mmTransverse deformation of
structure/mmTrack deformation/mm Structural crack Line 2 −1.28 0.5 −1.36 No Line 3 −1.01 0.5 No -
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