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.

Allowance of Lateral Breakthrough Error for Super Long Tunnels from 20km to 50km

Up to now there is no specification about the allowance of lateral breakthrough error for super long tunnel from 20 km to 50 km. On the basis of the design of GPS networks located outside and inside tunnel traverse network, we propose a method for calculating the influence value caused by control surveying errors. Through a lot of simulative calculations and combination with piercing practice of super tunnels in Wan Jiazai Project, Shanxi province, we present an allowance table of lateral breakthrough error for super long tunnels from 20 km to 50 km.

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).

Effects of high modes on the wind-induced response of super high-rise buildings

For super high-rise buildings, the vibration period of the basic mode is several seconds, and it is very close to the period of the fluctuating wind. The damping of super high-rise buildings is low, so super high-rise buildings are very sensitive to fluctuating wind. The wind load is one of the key loads in the design of super high-rise buildings. It is known that only the basic mode is needed in the wind-response analysis of tall buildings. However, for super high-rise buildings, especially for the acceleration response, because of the frequency amplification of the high modes, the high modes and the mode coupling may need to be considered. Three typical super high-rise projects with the SMPSS in wind tunnel tests and the random vibration theory method were used to analyze the effect of high modes on the wind-induced response. The conclusions can be drawn as follows. First, for the displacement response, the basic mode is dominant, and the high modes can be neglected. Second, for the acceleration response, the high modes and the mode coupling should be considered. Lastly, the strain energy of modes can only give the vibration energy distribution of the high-rise building, and it cannot describe the local wind-induced vibration of high-rise buildings, especially for the top acceleration response.

Interference effects of two and three super-tall buildings under wind action

Most previous investigations on interference effects of tall buildings under wind actions focused on the wind induced interference effects between two buildings,and the interference effects of three or more buildings have seldom been studied so far due to the huge workload involved in experiments and data processing.In this paper,mean and dynamic force/response interference effects and peak wind pressure interference effects of two and three tall buildings,especially the three-building configuration,are investigated through a series of wind tunnel tests on typical tall building models using high frequency force balance technique and wind pressure measurements.Furthermore,the present paper focuses on the effects of parameters,including breadth ratio and height ratio of the buildings and terrain category,on the interference factors and derives relevant regression results for the interference factors.

Intelligent optimization of the structure of the large section highway tunnel based on improved immune genetic algorithm

As in the building of deep buried long tunnels,there are complicated conditions such as great deformation,high stress,multi-variables,high non-linearity and so on,the algorithm for structure optimization and its application in tunnel engineering are still in the starting stage. Along with the rapid development of highways across the country,it has become a very urgent task to be tackled to carry out the optimization design of the structure of the section of the tunnel to lessen excavation workload and to reinforce the support. Artificial intelligence demonstrates an extremely strong capability of identifying,expressing and disposing such kind of multiple variables and complicated non-linear relations. In this paper,a comprehensive consideration of the strategy of the selection and updating of the concentration and adaptability of the immune algorithm is made to replace the selection mode in the original genetic algorithm which depends simply on the adaptability value. Such an algorithm has the advantages of both the immune algorithm and the genetic algorithm,thus serving the purpose of not only enhancing the individual adaptability but maintaining the individual diversity as well. By use of the identifying function of the antigen memory,the global search capability of the immune genetic algorithm is raised,thereby avoiding the occurrence of the premature phenomenon. By optimizing the structure of the section of the Huayuan tunnel,the current excavation area and support design are adjusted. A conclusion with applicable value is arrived at. At a higher computational speed and a higher efficiency,the current method is verified to have advantages in the optimization computation of the tunnel project. This also suggests that the application of the immune genetic algorithm has a practical significance to the stability assessment and informationization design of the wall rock of the tunnel.

截至2023年底中国10km以上特长公路隧道统计与分析

在隧道行业相关单位的大力支持及既有统计数据的基础上,对截至2023年底中国已建成运营、正在建设、规划设计的共计74座长度10 km以上的特长公路隧道进行统计,其中,已建成运营特长公路隧道25座,正在建设特长公路隧道31座,规划设计特长公路隧道18座。从隧道长度、所在省份、公路等级、地理位置、技术标准、施工工法、设计与施工单位等方面,对中国已建成运营、正在建设、规划设计的长度10 km以上的特长公路隧道建设情况进行分析,其中:长度在10~14.9 km的隧道共62座,长度在15~19.9 km的隧道共10座,长度大于20 km的隧道共2座;隧道主要集中在中国西南部,约占63%,四川省最多,其次是云南省;高速公路隧道达65座,占比约为88%;山岭公路隧道68座,水下隧道6座;隧道技术标准以双向4车道为主;隧道施工工法以钻爆法为主,近些年出现了TBM+钻爆组合工法;隧道设计单位主要有31家;隧道施工单位主要有52家。

沈阳恒隆市府广场超高层塔楼风荷载分析研究

为了确定高度350.6m沈阳恒隆市府广场塔楼结构设计的风荷载,采用刚性风洞试验与风洞数值模拟相结合的方法分析塔楼的风荷载,风洞试验研究给出楼层剪力与扭矩及风致加速度。采用四种湍流模型进行风洞数值模拟,分析建筑平均风压系数、体型系数、基底剪力及倾覆力矩,并与风洞试验进行比较,得出适用于超高层建筑风洞模拟的湍流分析模型,利用该分析模型的数值风洞模拟技术,分析塔楼13个风向角的风压系数、体型系数和基底剪力,为结构风荷载取值提供依据。研究结果表明:相比于《建筑结构荷载规范》(GB 50009—2012)对近似矩形平面建筑物的体型系数的规定,RSM模型迎风面0.83、背风面-0.56,与规范矩形截面迎风面0.8、背风面-0.6最为接近;RSM模型与试验吻合最好;选取RSM模型来分析超高层等大型复杂结构风荷载,能够得到较为准确的结果。

SAP联合双液浆对软土地区隧道漏水漏砂封堵效果试验研究

在高承压水软土地区盾构隧道修建过程中经常出现漏水漏砂险情,注浆封堵是常用的抢险方法之一。而在承压水层或者地层出现空腔情况下注浆时,传统的双液浆在注入后抗冲刷能力差,浆液留存率较低,严重影响抢险效率,难以在抢险的黄金时期控制住险情。因此,提出一种隧道漏水漏砂抢险的新型注浆方式,即高分子吸水树脂(SAP)与双液浆联合注浆,并通过室内模型试验研究了此方法的有效性,分析SAP注入方式、SAP种类、双液浆水灰比、渗漏流速等对注浆封堵效果的影响,并探究最优的注浆方式与封堵机理。研究结果表明,SAP吸水后,颗粒大、动水留存率高、吸水速度不受温度影响,能够填充地层侵蚀空腔,封堵渗漏或者减小渗漏水流速。本文试验条件下,以水泥浆液为载体注入SAP为最优注入方式,水灰比0.6的水泥浆液与吸水后的B类SAP均匀混合后,与水玻璃进行双液注浆,能避免跑浆,实现地层空腔与渗漏水的完全封堵。本文提出的新型注浆方式能够大幅增加双液浆的动水留存率,同时弥补SAP强度较低的缺陷,保证注浆体的整体性和地层支撑性,实现基坑与隧道等地下工程漏水漏砂灾害的快速有效控制。

超大埋深软岩隧道平行导洞合理超前距离研究

为解决滇藏铁路丽香线哈巴雪山隧道施工过程中产生的大变形问题,采用数值模拟、现场监测的方法,对哈巴雪山隧道不同平行导洞超前距离下隧道变形及正洞区域应力进行研究,提出平行导洞的合理超前距离。研究结果表明:1)哈巴雪山隧道平行导洞超前正洞的距离应设定为100 m,此时平行导洞对正洞区域的应力释放效果已达90%以上。2)平行导洞的设置使正洞拱顶沉降减小6.92%,上台阶水平收敛减小14.58%,下台阶水平收敛减小10.8%。由此可知,平导超前开挖能够减小正洞支护变形,对正洞水平收敛的控制效果大于拱顶沉降。

秦岭天台山超长公路隧道群关键技术创新与实践

针对秦岭天台山超长公路隧道群在建设和运营过程中面临的工程建设难度大,运营管理复杂、安全风险高以及运营能耗高等诸多技术难题,围绕安全智慧运营、安全快速施工、单层衬砌支护、自然能源利用等方向,系统总结了秦岭山区特殊地质地形条件下32 km隧道群建设与运营过程中系列创新技术成果。主要结论:1)通过超长隧道群安全智慧运营技术创新与应用,破解山区超长连续公路隧道群运营安全保障难题;2)通过公路隧道安全快速施工技术创新与应用,突破超长大断面公路隧道机械化安全快速施工瓶颈;3)通过公路隧道单层衬砌支护技术创新与应用,构建硬质岩公路隧道单层衬砌支护体系;4)通过公路隧道利用自然能源技术推广应用,探索超长公路隧道绿色低碳运行。

某核心筒收进水瓶型超高层结构设计关键问题研究

某超高层建筑位于武汉市汉阳区一线滨江区域,整体造型为下大上小逐渐收分的水瓶型,主体结构高度249m,屋面上设51m高塔冠,地上建筑总高度300m。建筑师要求外框柱贴幕墙边布置,导致塔楼大部分柱均为斜柱,在竖向荷载作用下将对楼面体系产生水平分力,设计中通过在楼面梁设置抗拉钢筋及型钢承担水平拉力。核心筒墙体在17、43层进行了转换收进,通过合理的分析及措施,确保了墙体传力路径的合理性。对主体结构进行了风洞试验并进行了相关论证,减小了设计风荷载,节约了结构造价。对结构进行了施工模拟、收缩徐变分析、墙体有限元分析及塔冠分析,结果表明结构设计安全合理。

凤凰山特大断面黄土隧道五步单侧壁导坑法研究

为解决特大断面黄土隧道采用双侧壁导坑法施工进度慢、成本高的问题,以G30连霍高速公路清水驿至忠和段扩容改造工程凤凰山隧道为背景,提出五步单侧壁导坑法。通过数值模拟对比分析双侧壁导坑法、五步单侧壁导坑法、传统单侧壁导坑法和台阶法在施工过程中的围岩变形及钢拱架应力,并结合现场试验段监测数据验证特大断面凤凰山隧道采用五步单侧壁导坑法施工的可行性。结果表明:1)五步单侧壁导坑法拱顶沉降和水平收敛比传统单侧壁导坑法分别减小3.59 cm和1.31 cm,比双侧壁导坑法分别增大1.4 cm和0.59 cm;钢拱架应力除拱肩外均小于双侧壁导坑法,最大处减少了70 MPa,钢拱架应力最大值与钢材屈服强度的比值比双侧壁导坑法增大0.04,比单侧壁导坑法减小0.08。2)传统单侧壁导坑法的安全性小于五步单侧壁导坑法,改进后的五步单侧壁导坑法相比双侧壁导坑法能在控制围岩变形的同时加快施工进度,降低施工成本。3)五步单侧壁导坑法中隔壁的最优位置应结合具体工程情况进行单独优化计算,针对本工程而言,其最优位置为45%洞宽。

超大直径盾构下穿高铁路基的沉降数值分析

为探究超大直径盾构隧道下穿城际铁路路基沉降规律,以中国武汉两湖隧道工程为例,基于Plaxis有限元软件,建立了铁路路基-土体-隧道的三维精细化数值模型,探讨盾构掘进过程中地层损失率、开挖面支护压力、盾尾注浆压力对隧道上方城际铁路路基沉降的影响.结果显示,盾构下穿复合地层的过程中,高铁路基道砟层表面在盾构掘进方向上会发生不同程度的沉降;当盾构掘进引起的地层损失率从1.0%增加到1.6%时,铁路路基的最大沉降从18.86 mm增加到22.71 mm,增大了20.4%;当开挖面支护力处于隧道拱顶侧向静止土压力的0.7~1.4倍时,不同工况下盾构掘进引起的铁路路基变形差异较小(小于0.67 mm);注浆压力对铁路路基的沉降影响明显,随着注浆压力增大,铁路路基的沉降明显减小.当隧道拱顶注浆压力增大到拱顶侧向静止土压力的3倍(648 kPa)或以上时,沿铁路路基的最大差异沉降未超过规范要求(≤5 mm/10 m).研究结果可为超大直径盾构下穿高铁路基时掘进参数的设置提供参考.

考虑土拱效应的超大断面隧道上覆土影响因素分析

超大断面隧道上覆荷载是隧道支护结构设计的关键参数。依托某超大断面隧道工程,建立数值模型分析不同覆土厚度与洞径之比下土层黏聚力、内摩擦角和剪胀角对隧道上覆土竖向应力的影响。结果表明:随着覆土厚度与洞径之比增加,土拱效应逐渐显现;各地层参数对隧道上覆土竖向应力的影响程度由大到小依次为内摩擦角、黏聚力、剪胀角。

台风作用下深圳新世界中心风致响应实测与风洞试验研究

依据近10年来监测到的5次强台风过境期间深圳新世界中心的实测响应数据,分析了该建筑结构在台风影响下的响应特点和模态参数变化特性,并将实测结果与粗糙度指数α分别为0.22,0.30和0.35地形下的风洞试验结果进行了比较。结果表明:历次台风影响下实测建筑达到最大振幅附近时均表现为明显的横风向振动,且最大振动方向均为南北方向;实测最大峰值加速度为17.28 cm/s^(2),满足舒适度要求;台风过境时,建筑结构模态频率表现出明显的振幅依赖性和时变特性,采用“时变”方式描述更加合理,几次台风过程的结构模态频率均是随时间先减小,在最大风速时达到最小值,然后增大并恢复到常态值;结构模态阻尼比在中低振幅区域分布较为离散,随着振幅的增加,阻尼比有所增大,顺风向和横风向的阻尼比最大分别为1.9%和1.2%;实测结果更接近于α为0.35地貌的风洞试验结果,显示C类地貌的风洞试验结果偏于保守。

超长隧道平面控制测量横向贯通误差预估研究

相向开挖20 km以上的超长隧道,洞内施工环境复杂,相关的洞内外横向贯通误差影响因素的综合分析案例较少,也无超长隧道测量的相关标准规范,导致洞内测量横向摆动难以控制。为给超长隧道建设提供贯通前误差预估,本文分析了横向贯通误差来源,研究了洞外、洞内控制测量对横向贯通误差的影响规律,估算了洞外GNSS、测角误差、测距误差等对横向贯通的影响值,设计了洞内仿真计算试验,试验顾及了对中误差、观测误差等因素。在不同测角精度、不同导线边长条件下,推导并仿真计算了20~30 km范围内不同隧道长度的洞内横向贯通中误差值。结果表明,提高测角精度对横向贯通精度增益效果明显,仿真计算的结果准确可靠,且以2 km隧道长度为划分区间,获得了超长隧道洞外、洞内横向贯通中误差的推荐值。