盾构无障碍始发与接收施工力学行为及施工工艺

发布时间：2018-05-22 14:19

本文选题：盾构无障碍始发与接收 + 端头土体稳定性　；参考：《北京建筑大学》2017年硕士论文

【摘要】：盾构法施工分为盾构始发、盾构掘进、盾构接收这三个阶段。其中,盾构始发与接收普遍存在土体坍塌、涌水涌砂、地下管线破裂等工程事故,安全问题较为突出。针对常规的盾构始发与接收工程事故频发的安全现状,本文在已有相关研究成果的基础上,采用理论分析、数值分析、现场试验等方法,进行了盾构无障碍始发与接收端头土体稳定性、施工力学行为、施工工艺等方面研究,获得如下成果:1.采用理论分析的方法,建立了盾构无障碍始发与接收端头土体的稳定性模型,提出了判定洞口处土体稳定性的数学模型表达式,研究结果表明:(1)洞口处玻璃纤维筋混凝土围护结构应同时满足背后水、土压力对其产生的抗弯、抗剪承载力要求。(2)认为在盾构无障碍始发与接收时端头土体不存在滑移失稳破坏现象,建议可取消端头土体加固。2.采用Flac3D数值分析的方法,以玻璃纤维筋混凝土围护桩体、洞口开挖面土体、地表沉降为研究对象,进行了盾构无障碍始发与接收宏观角度的施工力学行为研究,研究结果表明:(1)无障碍始发切桩过程中,当桩体切削至一半之后水平位移增幅会达到125.71%,应控制盾构推力,防止因桩后土体被动土压力导致过大的地表隆起。(2)无障碍始发时桩体水平位移及最大主应力均在允许值范围内,桩后土体稳定,地表隆起极小。(3)无障碍接收时,盾构在距洞口1倍洞径+(2~3)环管片时进入有限土体。之后,土仓压力随有限土压力协调变化,从而同时满足围护桩体与地表的变形要求。3.采用PFC3D数值分析的方法,进行了微观角度的盾构切桩过程及切桩机理的研究,研究结果表明:(1)盾构切桩过程中玻璃纤维筋混凝土开裂是一个裂缝产生、裂缝扩展与裂缝聚结的过程;桩体应力与切刀切削力均表现出先逐渐增大,后逐渐减小,最后趋于稳定的变化规律。(2)切桩过程中,应避免过大的盾构推力导致的围护桩体朝向基坑临空侧整体倒塌这一工程事故的发生。(3)就盾构无障碍始发而言,盾构切桩机理为全过程的剪压破坏;就盾构无障碍接收而言,盾构切桩机理为先剪压破坏,后剪切破坏的“两阶段模型”。4.以北京地铁16号线某盾构工程为背景,采用现场试验的方法,进行了盾构无障碍始发与接收施工工艺的现场实施研究,研究结果表明:(1)盾构无障碍始发分为刀盘密贴围护结构、切削围护结构、土仓压力建立并达到平衡稳定三个阶段;盾构无障碍接收分为进入有限土体、刀盘接近并密贴围护结构、切削围护结构三个阶段。(2)盾构无障碍始发有利于土仓压力与土压平衡的快速建立。(3)盾构无障碍接收有效提高了工程安全性和工程效率;切桩时应控制盾构贯入度在6mm左右。
[Abstract]:Shield construction is divided into three stages: starting of shield, tunneling of shield and receiving of shield. There are many engineering accidents, such as soil collapse, water gushing and sand gushing, underground pipeline rupture and so on. In view of the current situation of frequent accidents occurring in the conventional shield tunneling and receiving engineering, this paper adopts the methods of theoretical analysis, numerical analysis, field test and so on, on the basis of the related research results. The soil stability, construction mechanics behavior and construction technology of shield tunneling are studied in this paper. The results are as follows: 1. By using the method of theoretical analysis, the stability model of the soil mass at the beginning and receiving end of shield tunneling is established, and the mathematical model expression for judging the stability of soil at the hole is put forward. The results show that the concrete retaining structure of glass fiber reinforced concrete at the opening of the tunnel should satisfy the back water at the same time, and the earth pressure can resist the bending of the structure. The shear-bearing capacity requires that there is no slippage failure in the end soil mass when the shield machine starts and receives without obstacles, and it is suggested that the reinforcement of the end soil mass should be cancelled. Using Flac3D numerical analysis method, taking glass fiber reinforced concrete enclosing pile body, excavation surface soil and ground subsidence as the research object, the construction mechanics behavior of shield tunneling from the angle of unobstructed origin and receiving macroscopical angle is studied. The results show that the horizontal displacement increases to 125.71 when the pile body is cut to half in the process of unobstructed initial pile cutting, so the thrust of shield machine should be controlled. When the horizontal displacement and the maximum principal stress of the pile are within the allowable range, the soil behind the pile is stable, and the surface uplift is very small. The shield machine enters the finite soil when the annular pipe is 1 times the diameter of the hole. After that, the pressure of soil bunker changes harmoniously with the finite earth pressure, which satisfies the deformation requirement of retaining pile and surface simultaneously. In this paper, PFC3D numerical analysis method is used to study the process of cutting pile and the mechanism of shearing pile. The results show that the cracking of glass fiber reinforced concrete is a crack in the process of shearing pile. In the process of pile cutting, the stress of pile body and the cutting force of cutting tool increase gradually, then decrease gradually, and finally tend to change steadily. It is necessary to avoid the occurrence of the engineering accident that the shield pile body collapses towards the empty side of the foundation pit caused by excessive shield thrust.) in the case of shield tunneling, the mechanism of shearing pile cutting is the shear compression failure of the whole process; in the case of shield machine receiving without obstacles, the mechanism of shield cutting pile is the shear compression failure of the whole process, and the mechanism of shield cutting pile is the whole process of shear compression failure. The mechanism of shield cutting pile is the "two-stage model" of first shear compression failure and later shear failure. Based on a shield tunneling project of Beijing Metro Line 16, a field implementation study on the starting and receiving construction technology of shield tunneling is carried out by using the method of field test. The results show that the barrier free construction of the shield machine is divided into two parts: the cutlery close enclosing structure. Cutting enclosure structure, earth chamber pressure establishment and achieving balance and stability, shield machine without obstacles received into a limited soil, cutter head close and close to the envelope structure, It is beneficial to establish the balance between earth pressure and earth pressure in shield machine, which can improve the engineering safety and engineering efficiency effectively, and control the penetration degree of shield tunneling at 6mm when cutting pile.
【学位授予单位】：北京建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U455.43

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