Assessing the influence of jet-grouting underpinning on the nearby buildings

This paper focuses on the underpinning-induced ground movement due to jet-grouting. Jet-grouting technique can cause distortions as a result of an inaccurate processing sequence and/or errors made at different stages of work execution. The aim of this paper is to determine the minimum value of such movement on the basis of the findings obtained at two similar construction sites located in the Historical Center of Moscow, considering that the maximum value is usually unpredictable. Numerical simulation of the process of soil eroding agrees well with the observational data at the current stage. It was found that the minimum value of deformations （only settlement was considered in this study） due to jetgrouting is no less than 2-3 mm. By contrast, the negative scenario of deformation due to foundation underpinning is clearly demonstrated. Also, this paper provides some general solutions for excavation supporting system as well as for underpinning design.

Structural Design of a Tall Building with Underpinning Structure in Guangzhou

This paper introduces the structural design optimization of a tall building with reinforced concrete frame-core shear walls in Guangzhou downtown.To decrease the construction cost,wide flat beam with 400 mm ×650 mm rectangular cross-section are adopted for main beam.Special measures are used to decrease noncoincident centers of mass and stiffness.Because subway tunnels cross the building underground,inclined columns,the second and third floor underground together function as the underpinning structures.Different from traditional transform beam,the proposed underpinning structures show good performance without using large dimensional bending members.Special attentions should be paid to the beams connecting with the inclined column in the underpinning structures,and these beams show large tensile or compressive forces.Settlement observations after completion construction indicate that the building as well as the proposed design measures work well.

A Study of Underpinning Methods Used in the Construction Industry in Nigeria

Foundation and retaining wall failures account for the highest case of structural failures.This is a report on a study of underpinning methods used in the construction industry in Nigeria.In view of underpinning,just like most engineering decisions,there is no unique solution,the research investigated technique of remedying foundation defects and whether there are innovations as regards to the underpinning methods used in Nigeria.To achieve the desired objective structured questionnaire,oral interviews and case study of an ongoing underpinning work were carried out.Result shows that differential settlement with a mean of 2.28 is the most frequent cause of foundation failure.While the continuous strip and reinforced mat with mean of 2.7 and 2.67 respectively,are most frequently used underpinning methods in Nigerian construction industry.Also 81.3%of the respondents agree that underpinning methods adopted are suitable and effective.Professionals in Nigeria have devised unique method of underpinning.It was recommended that proper and adequate site investigation should be carried out.Heavy penalties and sanctions should be meted on those construction firms that employ quack professionals.

Plastic zone distribution laws and its types of surrounding rock in large-span roadway

In order to study the distribution laws and types of plastic zone of surrounding rock in large-span roadway, we analyzed the distribution laws with different spans and lateral pressures using FLAC3D numerical calcu- lation software. Based on the roadway support difficulty and distribution laws of the plastic zone of sur- rounding rock, we defined the large-span roadway and classified the types of large-span rectangular roadways. As a result, the distribution laws of the plastic zone on surrounding rock in a rectangular roadway with different spans and lateral pressures were obtained. The results show that the area of the plastic zone on surrounding rock increased with the increase of the spans and lateral pressures, and the plastic zone was symmetrical to the center line of roadway. At λ=0.5, 1.0, 1.5, and 2.0, the plastic zone presented ＂addle- shape＂ distribution, ＂ellipse＂ distribution, ＂thin and high＂ distribution and ＂inverse trapezium＂ distribu- tion, respectively. In addition, we classified the roadways into four types according to the different lateral pressures and spans, including small-span, moderate-span, large-span and extreme-large-span roadways.

Development of a new type of foam concrete and its application on stability analysis of large-span soft rock tunnel

The long-term stability of large-span soft rock tunnel is influenced greatly by the creep effect of surrounding rock.The development of a new type of foam concrete which has the property of high compressibility and low ductility was introduced.And it was made as filling material of reserved deformation layer between the first lining and the second lining used in large-span soft rock tunnel.The effect of the new type of foam concrete was simulated as filling material of reserved deformation layer using numerical simulation.Through the comparison with the common large-span soft rock tunnel,the vault settlement and surrounding convergence are reduced by about 61% and 45%,respectively,after creep of 100 a.And in the second lining,the plastic zone reduces apparently and the maximum equivalent plastic strain decreases relatively.So,it can be found that the application of the new type of foam concrete as the filling material of reserved deformation layer can relieve the excessive force in second lining induced by rock creep,reduce its deformation and improve the stability of tunnel.

In Situ Experiments on Supporting Load Effect of Large-span Deep Tunnels in Hard Rock

A section of the Nanliang high speed railway tunnel on Shijiazhuang-Taiyuan high-speed passenger railway line in China was instrumented and studied for its mechanical properties and performances. The cross section for the tunnel was300 m2and is classified as the largest cross section for railway tunnels in China. Through in situ experimental studies, mechanistic properties of the tunnel were identified, including the surrounding rock pressure, convergences along tunnel perimeter and safety of primary support and lining structure.Based on the field measured data, the surrounding rock pressure demand for large-span deep tunnel in hard rock is recommended as double peak type in the vertical direction and fold line type was recommended for horizontal pressure. The results suggested that Promojiyfakonov's theory was most close to the monitored value. Specific recommendations were also generated for the use of bolts in tunnel structures.Numerical simulation was used to evaluate the safety of the tunnel and it confirmed that the current design can satisfy the requirement of the current code.

Seismic response of large-span spatial structures under multi-support and multidimensional excitations including rotational components

To achieve rational and precise seismic response predictions of large span spatial structures(LSSSs),the inherent non-uniformity and multidimensionality characteristics of earthquake ground motions should be properly taken into consideration.However,due to the limitations of available earthquake stations to record seismic rotational components,the effects of rocking and torsional earthquake components are commonly neglected in the seismic analyses of LSSSs.In this study,a newly developed method to extract the rocking and torsion components at any point along the area of a deployed dense array from the translational earthquake recordings is applied to obtain the rotational seismic inputs for a LSSS.The numerical model of an actual LSSS,the Dalian International Conference Center(DICC),is developed to study the influences of multi-support and multidimensional excitations on the seismic responses of LSSSs.The numerical results reveal that the non-uniformity and multidimensionality of ground motion input can considerably affect the dynamic response of the DICC.The specific degree of influence on the overall and local structural displacements,deformations and forces are comprehensively investigated and discussed.

Characteristics of wind pressure pulse on large-span flat roofs

The wind pressure pulse events, among the most important characteristics of wind pressure fluctuations on large-span flat roofs, were investigated by wind tunnel tests in this paper. Incorporating the formation mechanism of wind pressure pulse events, the peak over threshold method was employed to study properties of this kind of events. The event duration time, the energy contribution, the number of the pulse events, and the distribution of average peak pressure were calculated. Probability density functions of some typical samples in separation region were also given. Results show that the non-Gaussian roof pressure is strong in the flow separation region owing to the wind pressure pulse events. Evaluations of the extreme peak pressures, which can be determined by the peak over threshold method effectively, are important to the design of building cladding.

习近平文化思想的核心内容与哲学底蕴

习近平文化思想内涵十分丰富,蕴含着深刻的哲学智慧,在党的宣传思想文化事业发展史上具有里程碑意义。习近平总书记关于把文化建设摆在全局工作的重要位置、“两个结合”的重大论断、创造人类文明新形态以及在文化自信自强中推进中国式现代化的重要论述,构成了习近平文化思想的核心内容。习近平文化思想对马克思主义哲学原理的运用主要体现在:人民至上是其唯物史观品格,实践第一是其认识论源泉,守正创新是其辩证法思维特质。习近平文化思想饱含丰富而深邃的中国哲学智慧:“明体达用、体用贯通”化用了中国哲学“体用之辩”的精髓要义,开放包容体现了中国哲学海纳百川、兼收并蓄的思维智慧,胸怀天下生动诠释了中国哲学的天下观和交往理念。

Research on Construction Control Technology of Large-Span and Small Clear Distance Underpass High-Voltage Line Tunnel

Hanping tunnel is a control project of national highway 310 Dahejia to Qingshui highway project.It needs to cross a 330kV high-voltage transmission line under the condition of small clear distance,which requires high construction requirements.In view of the difficulties such as shallow buried depth of tunnel and small clear distance between tunnel and tower of high-voltage line,multiple excavation blasting method is adopted,and smooth blasting,charge quantity control and damping hole setting are comprehensively used to reduce the impact on the tower and structure of high-voltage line.In order to ensure the smooth progress of the project,the large-scale finite element analysis software is used to simulate the whole excavation project.The influence of the full-section method and the middle partition wall method(CD method)on the surrounding rock and the high-voltage electric tower is compared.It is found that the CD method can effectively control the displacement of the surrounding rock and the tower on it and the uneven settlement.

Distribution characteristics and the evolution law of excavation damage zone in the large-span transition section of high-speed railway tunnel based on microseismic monitoring

Purpose–The microseismic monitoring technique has great advantages on identifying the location,extent and the mechanism of damage process occurring in rock mass.This study aims to analyze distribution characteristics and the evolution law of excavation damage zone of surrounding rock based on microseismic monitoring data.Design/methodology/approach–In situ test using microseismic monitoring technique is carried out in the large-span transition tunnel of Badaling Great Wall Station of Beijing-Zhangjiakou high-speed railway.An intelligent microseismic monitoring system is built with symmetry monitoring point layout both on the mountain surface and inside the tunnel to achieve three-dimensional and all-round monitoring results.Findings–Microseismic events can be divided into high density area,medium density area and low density area according to the density distribution of microseismic events.The positions where the cumulative distribution frequencies of microseismic events are 60 and 80%are identified as the boundaries between high and medium density areas and between medium and low density areas,respectively.The high density area of microseismic events is regarded as the high excavation damage zone of surrounding rock,which is affected by the grade of surrounding rock and the span of tunnel.The prediction formulas for the depth of high excavation damage zone of surrounding rock at different tunnel positions are given considering these two parameters.The scale of the average moment magnitude parameters of microseismic events is adopted to describe the damage degree of surrounding rock.The strong positive correlation and multistage characteristics between the depth of excavation damage zone and deformation of surrounding rock are revealed.Based on the depth of high excavation damage zone of surrounding rock,the prestressed anchor cable(rod)is designed,and the safety of anchor cable(rod)design parameters is verified by the deformation results of surrounding rock.Originality/value–The research provides a new method to predict the surrounding rock damage zone of large-span tunnel and also provides a reference basis for design parameters of prestressed anchor cable(rod).

论我国医疗救助托底功能的制度逻辑

托底保障是我国医疗救助制度的重要功能之一,该功能的确立应具有自身的逻辑自洽。托底功能的内涵逻辑体现在救助对象托底、医疗保障体系托底和医疗救助对象责任托底三个方面。在设定医疗救助托底标准时,除了与医疗救助托底功能所保障的公民权利相匹配外,还应综合考量制约医疗救助托底标准的相关因素。此外,医疗救助托底制度的施行也需遵循一定的逻辑。

考虑粘结滑移本构模型的托换梁承载特性分析

粘结滑移有限元分析是掌握型钢混凝土托换梁变形特性的关键手段。采用有限元分析软件建立了考虑和不考虑型钢与混凝土粘结滑移两种有限元模型,分析了托换梁荷载-挠度曲线、型钢应变及箍筋应变的变化规律。结果表明:不考虑粘结滑移时,托换梁的极限荷载、跨中挠度与试验值差值百分比范围分别为1.0%~6.8%和11.3%~24.5%,受剪段中部、梁跨中位置的腹板应变和内、外侧箍筋应变与试验值的差值百分比分别为23.1%、46.4%、15.8%和45.8%;考虑粘结滑移后,托换梁的极限荷载、跨中挠度与试验值差值百分比范围分别为0.7%~4.5%和5.7%~18.2%,受剪段中部、梁跨中位置的腹板应变和内、外侧箍筋应变与试验值的差值百分比分别为2.7%、1.3%、11.6%和27.7%;考虑型钢与混凝土粘结滑移的有限元模型可更准确地模拟梁的承载力和变形。

人行地通道下穿既有房屋基础改造工程案例分析

某新建人行地通道需要下穿既有房屋基础,需进行基础托换。对此类涉及既有房屋基础的改造工程,首先进行既有房屋的安全性鉴定,再根据鉴定结果以及业主需求进行改造设计,后由施工方按设计图纸进行施工。在施工过程中,采用了自动化监测措施,确保了施工顺利进行。该文介绍了某人行地通道下穿既有房屋基础改造工程过程,为类似工程实践提供一定的建议及借鉴。

流动·增容——基于结构托换技术的既有建筑改造设计方法

结构托换能够有效降低空间改造的工程量,是建筑改造工程朝向精细化、轻量化、低碳化发展的有效措施之一。结构托换技术与空间设计目标的协同需要跨专业的方法体系指导。文章从形态学视角概括了结构托换技术的类型及与其协同的空间设计策略,提出了结构与空间协同的托换空间设计方法,最后通过在南京小西湖街区部分建筑改造项目中进行实践验证,为托换技术与空间改造设计的协同运用提供了理论基础和实证参考。

异形板桥桩基托换力学行为及变形规律研究

随着地铁建设的迅速发展,不可避免的穿越既有城市立交桥,对其沉降及受力状态产生重大影响。依托石家庄地铁2号线下穿建和桥桩基托换工程,利用有限元软件,建立三维有限元模型,实现了桩基托换全过程模拟,通过数值计算得出了沉降变化规律,并与现场实际数据进行了对比分析。沉降结果表明,建和桥南桥托换部位沉降较大,应加强此区域位置的监控。通过分析桥面异形板及桩基应力历史,得出:桥面异形板在施工过程中应力变化主要集中在断桩施工阶段;原始桩基在托换施工全过程中,受力表现出先减小后增大的变化规律,新建桩基有效应力呈现出持续增长的现象;断桩施工将原始桩基受力有效转移至新建桩基,盾构施工对各结构应力状态影响较小。

基坑盖板下逆作车站地下连续墙托换破除技术

附属结构与地铁车站连通常需要对地下连续墙进行破除,当地下连续墙上设有临时承重盖板时破除的施工难度更大,风险更高。以某地铁盖挖逆作车站的地下连续墙破除施工为依托,提出了利用局部破除体作为临时竖向支撑进行托换破除的施工方法。首先,采用数值计算分析了不同托换间距对盖板结构体系的受力影响,综合施工进度和作业空间考虑,确定预留1m宽的临时托换柱和不大于12m的破除间距为控制指标,能够满足各受力结构体系在临时托换施工下的承载性能要求;其次,对盖板下地下连续墙破除及切割块转运施工进行了详细分析,给出了分块尺寸、切割块吊装、预留柱节点等关键施工环节的控制指标与做法。实施结果表明:利用既有地下连续墙作为临时托换结构进行破除地下连续墙的施工方法,安全可靠,施工速度快,成本经济。

框架柱托换节点抗震性能研究

为了研究框架柱托换节点的抗震性能,设计了5个包裹式托换节点,进行往复加载试验,分析结合面高度和界面钢筋对托换节点破坏形态和抗震性能的影响。建立了托换节点的非线性数值计算模型,验证了数值计算模型的正确性。试验和分析结果表明:结合面高度对托换节点的抗震性能影响显著,结合面高度为200 mm时,界面钢筋影响托换节点的破坏模式,托换节点的初始刚度随着界面钢筋数量的增加而增大;结合面高度为300 mm时,界面钢筋对托换节点的抗震性能影响较小。

2024年上半年经济形势分析与下半年展望

2024年上半年经济实现5.0%的增长,在复杂的外部环境与国内结构持续深化调整等各类挑战下,经济运行整体稳定。本文基于生产、需求、收入和价格分析框架,运用统计指标和统计数据,对上半年经济运行情况进行了分析,总结出上半年经济运行的主要特点:就生产端而言,第二产业保持较快增长,对经济增长的贡献明显回升;第三产业增速放缓,现代服务业保持快速增长。就需求端而言,消费需求对经济增长起主要拉动作用;投资需求拉动作用有所提升;净出口需求继续对经济增长做出贡献,货物出口结构继续优化。就收入端而言,居民收入保持平稳增长,增速有所回落;企业利润保持平稳增长。就价格端而言,消费领域价格涨幅较低,生产领域价格降幅持续收窄。本文还分析了2024年下半年经济增长面临的挑战和支撑点,对下半年经济发展情况进行展望,并提出下半年政策着力点。

地铁隧道下穿城市既有桥梁的数值模拟分析

为分析地铁隧道下穿既有桥梁的影响,以广州地铁某盾构隧道下穿既有桥梁为工程背景,建立三维有限元模型,分析了盾构隧道掘进施工对土体位移、隧道变形及桥梁变形的影响。通过数值模拟分析得出:土体位移、隧道变形及桥梁变形均满足变形控制标准要求,因此盾构隧道掘进施工不会危害桥梁结构的正常运营,既有桥梁在隧道掘进施工过程中是安全的。