Deformation Monitoring and Its Control in a Shallow buried Large span Tunnel Constructed Using the Pile Beam Arch Method

Deformation monitoring and control measures of a shallow buried large span tunnel constructed using the pile beam arch (PBA) method are described, taking the North Gongti Road Station of Beijing Metro line 10 as an example. Based on the monitoring datum, the crown settlement, convergence, ground settlement of the tunnel and the bridge foundation settlement are analyzed. The results show that (1) the PBA tunneling method can restrain the ground settlement and deformation of a shallow buried large span tunnel; (2) the depth, tunnel span and pilot tunnel construction may influence the deformation of a shallow buried large section tunnel significantly; and, (3) advanced conduit grouting, timely preliminary support and permanent lining construction can reduce the deformation effectively.     

Analysis on Deformation Characteristics of CFG Piles-Gravel Cushion Composite Foundation of the Deep Embedded Secret Passage

In order to investigate the issue in the field of the application of CFG pile application of CFG pile composite foundation technology in deep embedded secret passage of such special structure ground treatment, the settlement deformation of CFG pile composite foundation according to deep are studied and detailed analysis are given in the field test and indoor model test of the gravel cushion with different thickness. Moreover it points out that the cushion compressive deformation must be taken into account, and that the settlement deformation calculation cannot simply consider the amendments of composite foundation. The amendments of cushion deformation must be considered. The effect of the different thickness of cushion on pile-soil stress ratio, total settlement of composite foundation, cushion compression and axial stress of pile body were analysed by using ABAQUS finite element method. Through the analysis of the field test, indoor model test and the numerical simulation of CFG piles-gravel cushion composite foundation of the deep embedded secret passage, a settlement deformation monitoring method has been described and the selection principle of the cushion has determined so as to provide the cushion design basis in the process of composite foundation design.     

节理岩体中连拱隧道施工对周边建筑物的影响

以重庆东水门大桥—千厮门大桥渝中区连接隧道为研究对象,基于UDEC软件建立离散元数值模拟分析模型,研究了城区连拱隧道施工引起的地表沉降,上部建筑物基础沉降及倾斜,新建隧道下方已有轨道六号线的变形、受力特征,并将监测数据与数值模拟进行对比分析。结果表明,连拱隧道左侧隧道上导坑施工引起的隧道拱顶沉降和基础沉降量最大,经计算上部建筑物基础最大沉降量为3.81 mm,最大倾斜量为0.02%,建筑物基础沉降量和倾斜在规范许可范围之内;隧道施工引起的地层损失使得轨道六号线左拱肩向上隆起,六号线弯矩分布规律和其变形形态基本一致,弯矩最大值位于左拱肩部位,最大值为238 kN·m;数值模拟计算结果与监测数据量值相当,变形趋势基本一致;采用UDEC软件可以准确地计算出隧道开挖过程中节理的存在对隧道周围建筑物变形的影响。     

Analysis of bearing capability of CFG pile composite foundation

The CFG pile is used to consolidate the foundation in one passenger dedicated line. The field experiments including low strain dynamic testing, bearing capability of single pile and the composite foundation are done, and the bearing capability of composite foundation is calculated, too. The results show that the first and second class piles account for 93.9% and 6.1% respectively, and the bearing capability eigenvalues of single pile and composite foundation are larger than the designed values. The 3D FEM model is established to simulate the stresses of CFG pile top and inter-pile soil changing with load level, and the stress ratio between CFG pile and inter-pile soil is analyzed, too. The following results are got from the calculation results of FEM: 1) the stresses of CFG pile top and inter-pile soil increase with load level, but the increasing rate of the former is larger than the latter; 2) the stress ratio between CFG pile and inter-pile soil increases quickly when the load level is low, and it tends to convergent gradually with load increasing.     

Mechanical and Deformation Characteristicson Shield Tunnel Segment with Cracks

The 3D Goodman element is used to simulate segments' cracks in one section of shield tunnel in Guangzhou. Mechanical and deformation characteristics of segment structure responded to varied depth of cracks is analyzed in this paper. Meanwhile, research on coefficient of lateral earth pressure, soil coefficient and ground water level on mechanical and deformation characteristics is carried out. The research result shows that along with the increase of cracks' depth, the tensile stress, pressure stress reach the maximum value while the increment is not too much. However, when the depth equals to the thickness of segment, the reinforcements' tensile stress has increase sharply, even exceeded the allowable value. Moreover, the maximum number of tensile stress, horizontal and vertical convergent value of shield tunnel segment with cracks increase with the reduction of the coefficient of lateral earth pressure and soil coefficient, and increase with the increase of ground water level as well. Specific repair measure has been taken to segments' cracks in this section of shield tunnel based on the conclusions. In general, this section of shield tunnel is stable and safe now, and there is no longer new cracks appeared.     

Parameter Analysis of Effects of Axial Load on the Lateral Response of Piles

Based on the small deformation assumption, the equations of the laterally loaded piles influenced by the axial load were established. The effect of axial load on the lateral response of piles was studied with parameter analysis. The analysis shows that internal force and deformation of laterally loaded pile under axial loading is actually closely linked with the values of axial and lateral loads. In general, the high level axial load should be focused on. It is more significant that the effect of axial load on the internal force and lateral deflection of the upper part of flexible piles, while there is little effect on deep of long-thin pile foundation. The effect of axial load on the lateral response of pile is the largest as coefficient form of subgrade reaction increases linearly, while the effect is minimal as coefficient form of subgrade reaction is a constant. Except in case of buckling, the changes of axial load along the pile direction have little influence on the magnitudes of deflection and moment. The assumption that the axial load is constant with depth can meet the requirements of engineering.     

Numerical Simulation and Field Monitoring Research of Reinforcement Range of Soft Ground on One Side Road Widening Project

As one of common reinforcement measure, cement mix pile is widely used in soft ground treatment of road widen project, while relevant studies on reinforcement range is insufficient. According to the one side road widening project, the cross-section of deep soft ground is analyzed. When fill is simplified as trapezoid load, the conclusion that reinforcement depth of cement mix pile should greater than load breadth can be gained by addition stress distribution. Based on the numerical simulation of different reinforcement measures, the slope stability, road settlement and horizontal deformation are influenced greatly by reinforcement range. Comparison research indicates that when the soft ground from slope toe to road shoulder is strengthened, the improvement effect is obvious. The numerical simulation and field monitoring resules show that reinforcement measure is suitable. Meanwhile, this study can provide reference to similar project.     

Real Simulation of 3 D Physical Model Testing for Metro Station Tunnel Construction

Based on the large scale conceptual model theory of similar material, a physical model of metro station tunnel excavation was simulated. The excavation process of metro station tunnel between existing double tubes also was simulated. Ground settling, soil deformation and displacement of specific points around tunnels were studied. The influence of a cast in place pile on reducing soil displacement was simulated. The dynamic mechanical behavior and deformation laws of the soil were obtained along with some useful conclusions. The conclusions are beneficial for guiding the construction and expanded excavation of metro station spaces between existing double tubes.     

Dynamic Response Analysis of High-rise Pile Cap-soil-structure under the Wave and Earthquake Action

Finite element software was used to simulate the internal force and deformation of high-rise pile cap-soil-structure under the wave and earthquake action. Meanwhile, wave force was calculated by using Morison equation, and the mechanical behavior of structure was simulated by inputing horizontal El-Centro wave. Then, the initial state and the state of the largest positive and negative acceleration were selected to study the structure according to the time history curve, and the displacement, bending moment, shear and axial force changes of pile foundation under wave and earthquake action were discussed, which was compared and analyzed with the structural response under the action of earthquakes solely. The result shows that the moment of front row of piles is biggest, and the force of pile bolck is the most dangerous; the axial force of the corner piles is the largest, and one of the center piles is the smallest under the action of wave and earthquake. When the wave forces and seismic forces are in the same direction, the displacement, moment, and shear force of pile bolck will be increased, on the contrary, the displacement, moment, and shear force of pile bolck will be decreased.     

水平荷载作用下斜坡刚性桩非线性分析

在综合分析现有水平荷载作用下桩基分析方法的基础上,建立了考虑桩侧土体受力状态的斜坡刚性桩力学模型;根据极限平衡原理,建立横向荷载作用下斜坡刚性桩弯矩和应力平衡方程;引入考虑斜坡影响的p-y曲线方法,提出了综合考虑桩侧土体极限承载力与水平抗力系数沿深度呈线性增加的侧向极限承载力与土体抗力承载力系数计算方法,同时,将该方法应用于计算实例,通过与已有有限元和理论计算方法对比分析,计算结果验证了本文方法的合理性与可行性;并利用该方法,分析了斜坡坡角、桩土接触面系数以及地基水平抗力系数对斜坡刚性桩承载特性的影响因素。分析表明:斜坡的坡角、桩土接触面系数对侧向荷载作用下斜坡刚性桩的荷载位移曲线影响明显,而桩侧土的抗力系数对侧向荷载作用下斜坡刚性桩的荷载位移曲线影响不明显。     

Contrast Analysis of the Reinforcement Effect of Pile-Net Composite Foundation

To investigate the effect of consolidation soft soil, three groups of model tests were designed. The first group was PVC pile-net composite foundation, the second was pile-cap-net composite foundation, and the third was PVC and sand pile composite foundation. Butter was coated and plastic membrane was covered on inner side wall of model cast to reduce border effect. The gauges were glued with epoxy on the surface of the model with PVC piles and geogrids to measure the stress of PVC piles and geogrids. Soil pressure cells were installed in the middle of piles and the top of the sand piles, and dial indicators were installed in the middle of road and road shoulder to measure deformations. It is that shown: 1) as for the distribution of the road settlement and the differential settlement, the settlements of the third group are the largest and those of the second group are the least; 2) in terms of the stress ratio of PVC pile and soil, the values of the first group and the third group are similar, while the value of the second group is much larger; 3) the change of geogrid strain is disorderly. There are periodic peaks in the strain of geogrid of pile top and periodic troughs in the soil between the piles. The geogrid strain of the second group measured in the corresponding spot is much larger than those of the other two groups. The results of three groups of tests illustrate that if the condition is permitted, it would be the best to adopt the scheme of pile-cap-net composite foundation, which has better reinforcement effect for soft soil.     

Advances in Monitorinq Methods of Downward Surface Net Radiation

Downward surface net radiation,the net energy of the earth's surface obtained through shortwave and longwave radiation process,is the main driving force for material and energy cycle in the whole earth system.In this study,the main research results of monitoring methods of downward surface net radiation at home and abroad in recent decades have been summarized,and main remote sensing radiation products produced according to various sensors have been introduced.Moreover,the monitoring methods of downward shortwave and long-wave radiation have been discussed,and their principles,advantages and disadvantages have been analyzed to provide scientific references for further study of downward surface solar net radiation in future.     

Load Analysis of Butteting Bridges by CFD

An improved computational method for buffeting forces of long span bridges, which substitutes the traditional wind tunnel test with the bridge segment model for CFD method, is proposed. In the case study of Tsing Ma Bridge, the pressure distribution induced by the wind field of the bridge decks was simulated. The nodal buffeting forces were computed and the local stress responses were obtained according to the CFD simulation and the refined finite element model. Preparation for buffeting induced fatigue analysis of bridges and structural health monitoring are provided.     

紧邻立交桥的连续墙受力分析和安全性评价

以深圳地铁车公庙交通枢纽7 & 9号线车站深基坑工程为研究背景,选取典型的监测断面,埋置混凝土应变计,进行地下连续墙的内力测试,分析了连续墙在深基坑开挖过程中的内力变化规律,并对连续墙的安全性进行了评价,得到以下结论:随着基坑开挖深度的增加,地下连续墙的内力变化越发明显,基坑负二层和负三层开挖对连续墙的内力变化影响较大,应重点关注和监测;根据现场测试数据得到两侧地下连续墙的内力变化并非完全一致,主要受到紧邻基坑开挖和周边建筑物的影响;最后计算得到地下连续墙处于安全状态。     

Technical Economy Analysis on Selection of Structure About Soldier Pile

Based on silt geological condition, aimed at cantilever pile and pile-anchor, using method of beam on elastic foundation ,through multiple combinations of pile spacing, diameter, embedded-depth at different levels of excavation depth, the impaction is discussed on the greatest displacement, maximum bending moment, the largest shear forces of supporting structure, and in different excavation, bolt locations impact on maximum horizontal displacement, the greatest moment of medial and lateral bending moment, the biggest shear force of pile and the axial force of bolt. By deformation control standards of supporting structure, the law and technically feasible program is found. Then combined with construction method of pile and current quota, technical economy is performed to find the economic plan and give suggestion to the project.     

Analysis on Foundation Pit Deformation of a Commercial Building in Hangzhou

The foundation pit deformation of a commercial building in Hangzhou is calculated by using calculation method related to foundation pit deformation. The calculation results by m method show that the maximum deformation is 29.2mm and the real maximum deformation is 174.6mm. The deformation character obtained by foundation coefficient method is different from the real deformation. There are lots of factors influencing foundation deformation. According to practical engineering condition, in this study, the influencing factors for soil parameters, bracing condition, condition for insertion of retaining wall into soil and construction speed are determined. The calculation method used is analyzed and modified. Finally, a useful and valid method for calculating foundation deformation is presented, by which the foundation pit deformation in practical project can be forecasted and analyzed.     

Analysis of Solid Fluid Coupling for Tunnel Excavation in Complicated Fractured Rock Masses

When tunnels are through water bearing section of fractured rock mass, a complex interaction process between rock mass deformation and fluid transportation is one of the most important reasons for water gushing, water bursting and mud bursting.To study the rock mass deformation and fluid transportation in tunnel excavation under complex geological conditions, a hydraulic model of complex crack rock mass was established from the relationship between the crack growth degree of surrounding rock in deep buried tunnel and the engineering scale, with which fracture network of different levels in rock mass could be considered simultaneously.Furthermore,a computer Fortran program was put forward to simulate the solid fluid coupling of excavation process of a deep buried tunnel.And it was found that the principal fractures had strong flowing action and network fractures had storage function and lag effect in seepage area.And the yield area of surrounding rock was increased under the coupling of seepage field and stress field.     

联合板索基础抗拔机理及容许上拔力

针对目前使用的既抗压又抗拔基础存在的缺陷和不足,构建了联合板索基础并获得了发明专利授权。在研究联合板索基础与扩底桩基础的抗拔机理基础上,研究了联合板索基础与扩底桩基础所能承受的极限上拔力,通过联合板索基础与扩底桩基础的对比研究,揭示了联合板索基础的抗拔机理,并借助扩底桩基础的上拔力容许设计值和稳定验算公式,解决了联合板索基础设计和稳定验算问题。     

Factors Influencing Deformation of Underground Diaphragm Wall in Deep Excavation Based on Centrifugal Model Test

To know well the impact on the deformation of underground diaphragm wall caused by soil excavation, centrifugal model tests reflecting Shanghai soft soil creep effects were designed, and finite element was used to calculate the deformation of underground diaphragm wall caused by different excavation timeline, sequence and width based on the top down construction method in the deep and large foundation pit of Shanghai Expo axis underground complex project. Centrifuge model tests and monitoring data indicate that the results of numerical calculation are approximately close to the horizontal displacement of the underground diaphragm wall measured in site, which reflects the deformation behavior of excavation. The results show that remained berm and middle plate have good control over the deformation of underground diaphragm wall. Most part of underground diaphragm wall deformation caused by soil creep occurs after the remained berm is excavated. So in order to decrease the deformation of underground diaphragm wall, it would be useful to conduct plate structures as soon as the remained berm is excavated. The excavation width of remained berm in the north part is less than that in the south part. It will be advisable to finally excavate the remained berm where there are protected objects nearby.     

Calculation of Influence on Longitudinal Deformation of Adjacent Tunnels Due to Excavation

Unloading of excavation of foundation pit has influence on adjacent tunnels, therefore it is important to predict the deformation of metro tunnels to ensure the operation of tunnel. The displacement effect due to the surrounding wall soil unloading of adjacent excavation was not considered by the theoretical analysis method, and the analysis procedure of FEM was usually too complicated to get a satisfied result, so the horizontal and vertical additional stress were calculated by the Mindlin solutions. Furthermore, the tunnel structure was considered as the beam with infinite length. The additional stress was imposed on the Winkler model and the governing equation was built up on the adjacent tunnel structure. Finally, displacements and internal forces of existing tunnels were obtained. Compared with the numerical simulation and an engineering case, the results of the presented formula are in good agreement. It can provide certain theoretical and calculation basis for metro tunnels influenced by adjacent excavation.