Numerical Simulation of Shield Tunnelling Under a Historic Building Based on the Local Stiffness Correction Method (DMSM)北大核心CSCD

The district modified stiffness method (DMSM) considers the effect of joints and hand holes on the stiff-ness of the lining ring, assuming the stiffness around the joint and hand hole is to be reduced and the stiffness else-where is not changed. Considering the stiffness reduction of the lining ring caused by the segment’s circumferential joint, the internal force of the lining structure, the ground surface settlement and the displacement response of the surrounding soil body induced by shield driving are analyzed by an HS small strain constitutive model, and a 3D FEM model is established to analyze the interactions among the tunnel, soil body and building to apply to the dou-ble-line running tunnel of Shanghai Metro Line 11, which crosses under a historic building. In contrast, a 3D numeri-cal model based on the routine method (RMM) is set up and a comparison with the site measured data is conducted,with results indicating that they agree very well. The simulation results show that the existing building not only changes the surface settlement trough but also largely reduces horizontal displacement at the corresponding measuring points of the settlement trough; the distortion values of the existing building are related to the positions of the tunnel face and the location of the building; and the final distortion doesn’t decrease after completion of tunnel construction, but major residual distortion remains. This simulation method provides a reference for the control of disturbances during shield construction in soft rock. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Construction Techniques for the Small-radius Curved Shield Tunnels in Water-rich Fractured Stratum with High Pressure北大核心CSCD

A variety of construction problems, such as bad cutting effects of cutters, unreasonable boring parame- ters and blowout, are often encountered during shield tunnelling under unfavorable geological conditions. Aimed at these construction difficulties of high pressure, abundant underground water, fractured rock stratum, long distance and small-radius curves of Fuzhou metro, the mechanical behaviors of cutting tools were analyzed through theoreti- cal calculations of cutter cutting force, then the reasonable cutter configuration, tunneling parameters and the proper time for cutter replacement were presented. Some measures, such as screw conveyor renovation, mucking control and lowering of groundwater, were adopted for controlling blowout based on practice. The stability of excavation face was analyzed by numerical simulation, and the measures for shield boring and posture control in the long distance and small radius curved tunnels were summarized. The conclusions are as follows: 1) when shield machine is driven in fractured stratum, the effect of lateral impact force produced by spalling rock on cutter will be very large and rein- forcement is needed for cutter; 2) cutter replacement should be taken at proper time based on muck samples in con- ditions of increasing of total shield thrust by 4 000-7 000 kN, cutter torque by 1 000-1 500 kN•m and driving speed smaller than 10 mm/min; 3) adopting screw conveyor device with innovative anti-blowout devices and control measures for ground precipitation and mucking, it controls blowout effectively; 4) the maximum axis offset and the height offset of segment meet the requirements of shield construction specifications during shield construction of long distance small-radius curved tunnel. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Research on the Dust Removal Technology for Shield Tunnel Overhaul Construction北大核心CSCD

The shield tunnel is an ultra-long linear space. It will cause a lot of dust during the tunnel maintenance and overhaul operation, which is extremely unfavorable to the physical and mental health of the construction personnel and the environment outside the tunnel. It is difficult to guarantee the ventilation effect of the linear space using the conventional dust removal technology, which directly affects the construction safety and overhaul period. Therefore, based on the overhaul of a cross-river tunnel in Shanghai, combined with Computational Fluid Dynamics (CFD) simulation, device optimization and process combination, a three-stage dust reduction standardization process for tunnel overhaul construction is proposed, namely taking a water sprayer at the working point to control the dust at the source (primary protection); installing electrostatic dust removal and water filtration dust removal equipment in the tunnel(secondary protection); and installing two sets of water curtain spray device at the two tunnel exits to prevent dusts from diffusing into the atmosphere. It explores the actual dust-reducing effects of different dust-removing measures and layout combinations, laying a technical foundation for green and efficient dust reduction. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Temperature Measurements and Tail Brush Replacement using Frozen Liquid Nitrogen for the Nanjing Weisanlu Tunnel北大核心CSCD

A scheme for stopping water by freezing liquid nitrogen and replacing the tail brush is presented in light of the situation encountered at the Nanjing Weisanlu river-crossing tunnel, a long-distance shield driving tunnel characterized by serious water leakage, sand gushing and water inflow at the shield tail brush. The law of the tempera-ture change of the master outlet circuits and each branch circuit when using liquid nitrogen freezing to stop water un-der high water pressures and the temperature change law for the soil body at different depths are analyzed. The re-sults show that: the temperature difference of the liquid nitrogen is large at the inlet and outlet of the freezing pipe,and it reaches around 35℃ after 6 days; the temperature drops fastest in the pebble layer, and the second fastest in the gravel sand layer, with the temperature cooling slowest in the silty fine sand layer; the average velocities at the frontal surface of the frozen soil in the pebble layer, gravel sand layer and silty fine sand layer are 15.5 cm/d, 12.5 cm/d and 8.3 cm/d, respectively, within the range 600 mm away from the frozen pipe; and affected by heat and air convection in the tunnel, the temperature at the junction of the segment and soil is higher than that in the soil layer.A complete frozen wall takes shape after 13 days of liquid nitrogen freezing, and tail brush replacement takes 22 days from freezing. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Full-scale Test on Ultimate Bearing Capacity of Tunnel Segment Lining with Staggered Joints北大核心CSCD

Aiming at the serious effect of soil and water loss on tunnel operation and safety, full-scale quasi-static loading tests were conducted regarding the ultimate bearing capacity of staggered erected tunnel linings in unload- ing situation. The design of tested lining and loading schemes were introduced. The test results, including the evolu- tion of deformation, segment crack, joint opening and bolt stress, were presented. The bearing capacity and failure mechanism of tested linings were discussed and analyzed. It shows load-displacement curve is of elastic-plastic form and the tendency of load-displacement curve is linearly rising; strength failure of circumferential joint occurs and the interaction between segments decreases, leading to decrease of integral rigidity; shearing failure of concaveconvex connector of circumferential segment joint, compression induced concrete failure of longitudinal joint and bending failure of the segment finally cause stability loss of the tunnel structure. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

动力作用下盾构隧道接头破坏行为研究

为揭示盾构隧道接头在高速列车动力撞击下的破坏行为,通过建立盾构隧道三维数值模型,对螺栓开裂与否两种工况下的管片接头破坏情况进行分析对比,同时捕捉管片接头与螺栓的动态开裂过程。研究结论:是否引入螺栓开裂对于管片纵向接头的开裂情况有较大影响,引入螺栓开裂后管片纵向接头部位不会出现完全破坏的单元,但其裂缝张开度总体上反而有所增大。撞击荷载下,管片纵向接头率先出现开裂的部位均为弯螺栓处,且环向弯螺栓呈环状断裂破坏,纵向直螺栓纵向剥离破坏。     

低地板有轨电车盾构隧道疏散平台设置研究

为了解决低地板有轨电车盾构隧道疏散平台设置困难、易侵限的问题,提出一种新的疏散平台设置方法,有效解决因曲线地段车辆设备限界加宽而需要增大盾构隧道直径的问题。通过对盾构隧道区间限界影响因素进行分析,发现随着车辆地板面高度的降低,疏散平台有效安装空间变小,尤其在曲线地段限界难以满足要求。针对此问题提出疏散平台曲线内侧设置和行车方向左侧设置两种解决方案,并对两种方案特点进行了对比,行车方向曲线内侧设置方案优于行车方向左侧设置方案,可以大大节约建设成本。该方案在佛山市南海区低地板有轨电车项目中进行应用,验证了该设置方法的有效性。     

盾构钢弹簧浮置板轨道结构高度不足的影响分析

受盾构结构空间狭小限制及施工误差影响,盾构中浮置板轨道结构高度不足问题在施工过程中普遍出现。为了研究此问题对浮置板受力和隔振效果的影响,本文针对目前此问题的常用处理措施,利用有限元软件建模分析这些措施对浮置板受力和隔振效果的影响。最终得出降低道床板厚度、减小隔振器纵向间距会增大浮置板1阶固有频率、降低浮置板的低频隔振效率,尤其道床板厚度的降低对浮置板隔振效果影响较大;隔振器纵横向间距减小会减小道床板内的拉、压应力,隔振器刚度增大会增大道床板内的应力。除此之外,目前的常用处理措施也会影响道床基底排水、浮置板施工及后期养护维修。     

软土盾构隧道施工阶段上浮量预测综述

随着我国各大城市地铁和江河海底盾构隧道的兴建,施工过程中管片上浮问题已成为当前亟待解决的关键技术问题。首先,从上浮作用机理、横纵向刚度联系、上浮力分布规律以及上浮计算模型方面综述国内外研究现状及存在的问题。其次,在已有研究成果基础上,提出可进一步研究的思路和方向。主要包括:(1)将浆液充填、渗透视为连续过程,探求浆液黏度时变性下管片上浮力分布规律和计算公式;(2)摒弃了传统等效刚度模型和"梁-弹簧"模型,提出横、纵向折中的"局部刚度修正梁-梁"模型;(3)指出弹性地基圆梁法和修正惯用法不适用于分析盾构隧道施工阶段上浮问题,提出抗力反转局部上浮计算模型;(4)考虑浆液时变性、地应力、上浮力以及上覆地层反向压缩特性等因素,创建基于等效刚度或"局部刚度修正梁-梁"思想的盾构隧道整体上浮计算模型。最后,对如何实现给出相应建议。     

提高土压平衡盾构掘进效率研究

为了在确保工程质量及施工安全的同时,进一步提高盾构掘进施工效率,获取更大的经济效益,根据土压平衡盾构施工特点,从盾构掘进的施工工序进行综合研究,以石家庄地铁1号线一期工程和平医院站-烈士陵园站区间施工为例,确定了影响盾构掘进效率的主要因素,并对掘进影响因素进行分析总结。得出了： 1)盾构掘进时间、管片拼装时间工序较为单一,主要和地质情况和作业人员熟练程度有关; 2)管片吊运下井时间、渣土吊运出井时间、其他外部原因对现场施工的影响等会受施工场地布置影响,在盾构施工前应进行合理的施工场地布置; 3)对盾构、后配套设备维修保养及易损件更换时间、盾构施工测量及移站影响时间的优化,能进一步提升施工效率。