【作者】 石刚强；

【导师】 张鲁新；

【作者基本信息】 兰州大学 ， 地质工程， 2014， 博士

【摘要】 穿越我国东北地区的哈大高速铁路于2007年7月28日开工建设,2012年12月1日开通运营,是世界上第一条在严寒地区新建和开通运营的高速铁路。为确保高速动车组安全平稳运行,采用有效合理措施,把路基冻胀控制在允许范围,是哈大高铁急需解决的关键技术难题。哈大高铁路基施工时采用各种措施方法系统处置了许多冻胀防治问题,但由于所处的特殊地理环境,目前路基冻胀变形还无法完全消除,在高速动车冲击荷载以及季节性冻融过程作用下,以冻胀变形为主要表现的路基变形成为影响线路稳定和行车安全的主要问题。因此,研究总结路基冻胀变形和工程对策,为完善路基防冻胀工程措施和线路养护维修提供基础依据及技术支持,同时也为同类工程设计和施工提供指导,具有现实价值。结合2012-2013年哈大高铁开通前后出现的路基冻胀现象及采取的整治措施,通过对路基冻胀变形人工观测数据、长期监测系统监测数据、典型试验断面监测数据和运营部门轨检车数据等的系统分析,研究了严寒地区无砟轨道结构下路基季节冻胀影响过程和冻胀特点及规律、路基冻胀的机理和主要影响因素。通过调研、室内试验、建立现场试验段、理论分析及计算,分析了影响路基冻胀的寒区工程环境、冻土环境特征及施工期已采取的防冻胀措施,研究了高速铁路路基填料冻胀特性、抑制路基季节冻胀的防冻胀措施与工程对策、效果评价。主要有以下创新结论：(1)严寒地区高速铁路路基季节冻胀具有普遍性和特殊性。无砟轨道路基结构的特性导致路基基床上部形成接近封闭的冻胀空间,这一封闭空间易造成水分聚集不利于水分散逸,具有离散性,在冻结过程中容易形成不均匀冻胀。(2)通过哈大高铁开通后首个冻融期(2012-2013年度)全线路基5000多个断面人工观测数据和42个断面自动监测数据综合分析,哈大高铁路基冻胀变形可分为冻胀初始波动、冻胀快速发展、冻胀稳定发展和波动融沉四个发展阶段,路基普遍发生冻胀但变形处于可控状态；路基冻胀变形以上层冻胀为主,路基的冻胀变形程度与路基结构有关,整体上全线过渡段冻胀轻微,路堤次之,路堑和底座板接缝处较为严重,最大冻胀量沿线路方向波动变化。(3)路基季节冻结深度沿线路方向自南至北呈增大趋势,现场观测最大冻深为标准冻深的1.2-1.6倍,平均为1.43倍,设计冻深应根据具体工点情况综合确定。路肩电缆槽的设置增加了地表水渗透至路基本体的通道,改变了路基本体的热对流条件,因此电缆槽不宜设置在无砟轨道路肩上。(4)通过室内试验研究、现场调查和观测数据分析表明,含水量是影响路基填料冻胀率的主导因素,掺水泥5%以上级配碎石硬化后基本消除了细粒土冻胀敏感性。在严寒地区高铁设计和路基冻胀整治中,将路基表层改性为不冻胀整体结构的思路可行,并提出两种新型路基防冻胀结构。(5)基于路基季节冻胀的普遍性采用了在季节冻深范围设置非冻胀土防冻层、路基表面设置纤维混凝土封闭层、路基基床底部设置两布一膜隔水隔断层、填筑防冻胀护道等防冻胀措施,经对监测数据的系统分析表明,全线冻胀量小于12mm的测点比例为96.9%,已采取的防冻胀措施对季节冻胀变形起到消除、减缓的作用。(6)针对路基季节冻胀的特殊性,以控制基床表层冻胀变形为整治工作的主要思路,提出改善基床填料性质、阻隔路基表面水分下渗、降低地下水位、局部保温改变冻胀发生条件是解决运营期路基季节冻胀的主要工程对策,观测数据表明,基床表层采用级配碎石掺水泥地段冻胀量基本都在4mm以下,设置渗沟地段不均匀冻胀降低21.1%,所采取的措施防治季节冻胀初步效果明显。(7)对主要防冻胀措施进行的数值计算模拟结果说明,动载作用下经防冻胀措施处理的加固路基在冻胀情况下,冻胀土体的弹性模量得到显著提升；融化季节水分不能瞬时排出,路基上部土体弹性模量降低有可能导致路基沉降变形变大,应引起关注。通过综合分析,提出了严寒地区高速铁路的路基状态评估的基本思路和方法。本文研究结果已经在哈大高铁路基设计施工、冻胀整治工程和线路运营维护中得到应用。目前夏季开行300km/h的高速动车组和冬季开行200km/h的动车组列车且安全平稳运行,证明所采取的季节冻胀防治工程对策对于解决严寒地区高速铁路路基冻胀问题是有效的和可靠的,并且能保证行车速度和行车安全。更多还原

【Abstract】 The Harbin-Dalian High-speed Railway(HDHR), acrossing the Northeast China, started construction in July28th,2007, and opened for operation in December1st,2012. It is the first new-built and operating high-speed railway in cold regions around the world. In order to ensure safety and smooth running of high speed multiple units, it is the key and urgent technical problems that the stringent using reasonable measures to effectively limit subgrade frost heave within allowable range.Although there have solved the problem of subgrade frost prevention by various methods in HDHR, but because of the special geographical environment, the deformations of subgrade frost heave are not completely eliminated. Under the action of impact load at high speed and seasonal freeze-thaw process, the frost heave deformation as the main performance of subgrade deformation become the major problems that affect line stability and driving safety. Therefore, through researching on subgrade frost heave deformation and engineering countermeasures, there would provide the basis and technical support in HDHR to ensure the safe and reliable operation, to improve engineering measures of subgrade frost heave, and to maintenance and repair track, as well as provide guidance for similar engineering design and construction. The dissertation, combining with phenomenon of subgrade frost heave and improvement measures before and after the HDHR opening in2012-2013year, by employing the methods of investigation and analysis, laboratory test, set field-test section, theoretical analysis and calculation, will make an analysis of the surrounding engineering and permafrost environment character in cold regions,anti-freezing measures having been taken during construction period which affect subgrade frost heav of HDHR, research on the process, characteristics and laws of seasonal frost heave on unballasted track subgrade through analysising data of subgrade frost heave deformation include artificial observation, long-term monitoring system, typical test section and track inspection railcar of operations department, etc. explore the mechanism and main factors of subgrade frost heave of high-speed railway,experiment the frost heaving characteristics of subgrade filling of high-speed railway in cold regions,and examine the suppressing anti-freezing measures and engineering countermeasures of seasonal frost heave of subgrade and make an evaluation about engineering effect. The main innovative result are listed as follows:(1) The seasonal frost heave of high-speed railway subgrade in cold regions has the particularity and widespread. The specially subgrade structure with ballastless track result in the upper of subgrade bed to form nearly closed frost heaving space. The enclosed space is easy to result in moisture gathering over water loss and it is easy to form the uneven frost in the freezing process.(2)The data during the first freeze-thaw period (2012-2013years) from5000artificial and42long-term automatic monitoring sections along the whole line were analyzed after the railway line was opened. The results show that the development of the frost heave includes the frost heaving occurring volatility, the rapid growing stage, the stable frost heaving stage and the thawing settlement stage. Althrough frost heaving deformation occurred along the whole line, the frost heaving values are under controlling. The frost heaving deformation main exists in upper of subgrade bed and deformation level related to the subgrade structures. As a whole, the frost heave in the transition section is slight and the embankments part is middle level and it is most serious in the cutting sections and base-plate jointing parts. The maximum amount of frost heave is fluctuated along the line.(3) The seasonally frozen depth of subgrade is increased along the direction of the line from the southern to the northern.The maximum frozen depth of field observation is1.2～1.6times of the statistics frozen depth of meteorological department and it is1.43times of average value, so we should be determined comprehensively the maximum frozen depth according to the specific worksite situation in the design. The shoulder cable groove increases channels of the ground surface water infiltration to the road basic body and result in changes the heat convection of subgrade body road so it is not necessary that track cable groove is arranged on the shoulder of ballastless track line.(4) Throught the indoor experimental research, field investigation and observation data analysis, it shows that water content is the dominant factor influencing subgrade frost heaving ratio. After graded crushed stone mixing cement by more than5%, hardening of the rubble basically eliminated the fine grained soil frost heave sensitivity.In cold regions, it is feasible to change the subgrade surface into without frost heave monolithic structure both design and subgrade frost heave control of high-speed railway.There are given two new anti-heaving subgrade structure.(5) Because of the universality of seasonal frost heave, non frost heaving soil layer in the seasonal frozen depth and arranging the fiber concrete sealing layer on the subgrade surface and setting two cloth a membrane isolate faults and water filling frost heaving protects measures are all set up. In addition, the system of monitoring data analysis shows that the measuring point of the frost heave less than12mm in the whole line accounted for96.9%, there had effect on eliminating and reducing the deformation of seasonal frost heave.(6) Because of the particularity of seasonal frost heave, the main way is to control the frost heaving deformation of subgrade surface layer for the rectification work. It put forward main countermeasures to solve the operating period of the seasonal frost heave of subgrade and that is to improve bed filler properties, to cut off the subgrade surface moisture infiltration, to reduce the underground water level, to change frost heave condition with partial insulation way. Observation data indicates that the frost heave of the bedding surface layer was mixed graded crushed stone with cement are essential below4mm, the uneven frost heave of setted sewer sections reduce21.1%, measures to prevent and treat seasonal frost heave obtained obvious effect.(7) Numerical analysis of main engineering countermeasures simulation conclude illustrates that under dynamic loads the modulus of elastic of frost heave is significantly improved in reinforcing subgrade section at frost heaving condition. In melt season because the water was not instantaneous discharged, modulus of elasticity of the subgrade upper part is reduced and it may lead to larger settlement deformation of subgrade, therefore we should pay more attention on it. By means of comprehensive analysis, the basic thought and method of assessment about subgrade status are put forward on high speed railway in cold regions.The research results of the project have been applied in design and construction of HDHR subgrade as well as renovation and maintenance of frost heaving. At present, high-speed multiple units are smooth running respectively in300km/h in summer condition and200km/h in winter condition. It proved effective and reliable of prevention measures for solving the issue of high-speed railway subgrade frost heave in cold regions and it can ensure mormal running of multiple units both regular speed and safety.更多还原