多线叠交盾构施工引起土体变形数值模拟分析

针对上海地铁十一号线徐家汇站至上海体育馆站施工区间隧道四线叠交的复杂穿越形式,采用三维有限元方法,模拟了多线叠交盾构隧道施工的整个过程。利用单元生死技术和重复设定单元属性等方法实现土体卸荷、盾构推进、管片拼装以及注浆硬化等动态施工过程,针对多线叠交盾构施工穿越既有隧道区域所引起的地层变形进行了分析,将得出的数值模拟结果与监测结果进行对比,研究结果表明,地表沉降最大值的位置与盾构机顶推面位置有一定关系;当两线隧道穿越完成后,地表沉降的最大值位置与单线隧道穿越引起的最大值位置相比会发生一定量的偏移。研究成果可以为多线叠交盾构隧道施工区域保护技术的实施提供一定的理论基础。     

Deep learning-based automatic detection of muck types for earth pressure balance shield tunneling in soft ground

For the earth pressure balance shield, the muck can reflect soil information at the tunnel face to track the change in geologic conditions. Thus, this paper presents a general framework for automatic detection of muck types based on the on-site surveillance camera using deep learning algorithms. A simplified muck classification method and the corresponding muck recognition criteria are proposed for the muck detection task. The muck detection model (MDM) based on You Only Look Once v4, is established on the muck dataset for Shanghai (MSH) after some optimization treatments. The mean average precision value of 97.73% of MDM is twice that of the original model of 48.47%. The MDM is then applied to Metro Line 14 in Shanghai. Results show that The MDM performs well and meets the real-time requirements with frames per second of 60, and it outperforms other state-of-the-art detection models both in accuracy and speed.     

Process and Outcome-based Evaluation between Virtual Reality-driven and Traditional Construction Safety Training

The emerging digital technologies such as virtual reality (VR) provide an alternative platform for construction safety training. In order to explore how digital-driven technologies affect the effectiveness of safety training, there is a need to empirically test the differences in performance between digital 3D/VR safety training and traditional 2D/paper approach. This research conducted a performance evaluation that emphasises both the training process and learning outcomes of trainees based on researchers’ self-developed immersive construction safety training platform. Data related to physiological indicators such as skin resistance were collected to measure safety performance before and after the training. The detailed measurement indicators included nine categories (e.g., immersion, inspiration) to form a holistic list of evaluation dimensions. The findings revealed that VR-driven immersive safety training outperformed the traditional way for trainees in terms of both process and outcome-based indicators. Results confirmed that safety training was no longer constrained by understanding or memorizing 2D information (texts and images). Instead, trainees experienced a stronger sense of embodied cognition through the immersive experience and multi-sensory engagement by interacting with the VR-driven system. By engaging the theory of embodied cognition, this research provides both the empirical evidence and in-depth analysis of how immersive virtual safety training outperforms traditional training in terms of both training process and outcomes.     

Scale model test of highway tunnel construction underlying mined-out thin coal seam

The construction of a highway tunnel adjacent to an overlying mined-out thin coal seam disturbs the surrounding rocks, thus affecting the stability of tunnel structures. This paper presents scale model tests in a 1g gravitational field on the tunnel excavation undercrossing the caved zone of the goaf. In the tests, different caved zone–tunnel distances (d) were considered as well as the inclined coal seam with different dip angles. Settlement on the roof and floor of the caved zone and vault settlement of the tunnel during excavation were tested and compared. It was shown that in the caved zone the settlement on the roof was greater than that on the floor. The caved zone also affected the vertical and lateral loads on the primary support of the tunnel. The results showed that d has great influence on the vertical pressure in the case of a horizontal coal seam while the dip angle affects the lateral pressure significantly for an inclined coal seam. This means that in the case of a horizontal coal seam, the closer the caved zone, the greater the average vertical pressure and the maximum bending moment, and the smaller the corresponding axial force. As for the inclined coal seam, the greater the dip angle, the larger the moment and axial force of primary support. A significant pressure bias was also revealed in the case of an inclined coal seam with the dip angle of 30°.     

Effect of the combination characteristics of rock structural plane on the stability of a rock-mass slope

The structural planes play an important role in rock mass slope stability. In this paper, a series of triaxial tests on the rock mass samples with different dip angles, plane numbers and plane spacing of structural surfaces were carried out to study the effect of the combination characteristics of the rock structural plane on rock mass mechanic parameters. Based on the test results and the combination characteristics of the field structural plane, the rock mechanics parameters for the spillway lock chamber slope of the Liyuan hydroelectric station were forecast. The stability of the slope was rationally evaluated based on the forecasted rock mass mechanical parameters. Finally, the safety factor was obtained based on the shear strength reduction method.     

系杆拱桥整体拖移施工技术研究

通过湖南某火车站内拱桥的施工实例,对跨繁忙既有车站系杆拱桥整体拖移技术进行了研究,该技术运用万能杆件拼装拖移平台,采用PLC控制系统进行拖移定位,对主拱和桥面线性、沉降及应力进行监控,保证了拼装的精确性。     

Evaluation of influence of vibrations generated by blasting construction on an existing tunnel in soft soils

The controlled blasting technique is employed, for the first time, on the diaphragm wall of an existing road tunnel in soft soils in the city of Shanghai, and therefore, safety demands on evaluation of influence of the blasting vibrations on the tunnel are highly required. Based on the practical blasting scheme of four sections of diaphragm wall of the tunnel to be exploded in three groups, the field monitoring of blasting vibrations is carried out on the bottom plate of the tunnel and the blasting vibration effects on the tunnel are measured throughout the blasting construction. The sequential characteristics of vibration velocities and accelerations of the tunnel structure are obtained from the field blasting tests. In order to fully understand the safety criterion of the blasting vibrations on the tunnel, a 3D numerical model is established by the finite element software ABAQUS. The numerical simulation results are confirmed by field monitoring data. Based on the monitoring data and numerical results of the tunnel subjected to blasting loads, results show: (1) the blasting energy is transferred mainly along the vertical direction; (2) the basic frequency domain of the tunnel responses caused by the explosion is relatively in a lower frequency range; (3) distinct vibration response spectra of the tunnel structure are observed along the horizontal and vertical directions; (4) the performance of the tunnel subjected to the blasting construction is in a critical state of safety and thus the blasting construction scheme should be implemented carefully. Finally, critical issues on evaluation of the blasting construction are fully discussed and evaluated, which provide a reference for other similar projects.     

近距离多线叠交盾构施工对既有隧道变形的影响研究

针对上海地铁新建11号线先下后上近距离穿越既有4号线,形成三层隧道四线叠交的特殊工况,采用有限元数值模拟和现场监测相结合的方法,考虑既有隧道周围土压力的分布规律,研究了盾构下穿施工时土仓压力和注浆压力以及上穿施工时压重范围和压重量对既有隧道变形的影响。研究结果表明：下穿施工结束时,既有隧道的沉降量不随土仓压力比的改变而改变,但随注浆压力比的减小而增大;上穿施工应采取压重措施预防既有隧道的上浮和局部隆起变形,宜遵循新建隧道同步压重为主,既有隧道压重为辅的原则。     

大型超深基坑工程计算理论与实践研究——上海外环隧道浦西基坑工程

上海外环隧道浦西基坑工程是一个开口型基坑 ,深度不等 ,宽 43m。通过采用超明星 (SUPER -STAR)空间非线性软件、美国SAP空间线性软件和北京理正空间线性软件对原设计的结构进行初步比较计算 ,确定采用超明星软件进行跟踪计算 ,针对实际工况 ,提前两周给出计算结果以指导施工 ,实践表明 ,计算与实测结果比较符合 ,说明该理论是合理可行的 ,跟踪方法也是有效的     

Simplified nonlinear simulation of shield tunnel lining reinforced by epoxy bonded steel plates

A high-efficiency simplified modeling approach based on fiber-beam elements and discrete elements is proposed for investigating the nonlinear response of shield tunnel reinforced concrete linings. The proposed approach focus on following main features: modeling simplicity and computational efficiency, the considerations of critical material and geometric nonlinearity associated with the entire loading process, including the stage of reinforcing the deformed concrete lining by steel plates. Comparison between the analysis results of the proposed numerical model and the experimental results from the full-scale structural test are presented to validate the developed model. The results show that the proposed model can capture the essential characteristics of the nonlinear load–deformation response of segmental tunnel lining. The modeling approach presents a balance between simplicity and accuracy, and serves as a viable alternative to detailed finite elements analysis.