斜坡软弱地基路堤工程特性及其双指标设计体系研究

发布时间：2018-01-17 20:22

本文关键词：斜坡软弱地基路堤工程特性及其双指标设计体系研究　出处：《西南交通大学》2014年博士论文　论文类型：学位论文

【摘要】：中国幅员辽阔,丘陵和山地广泛分布,交通基础设施建设中频繁遇到斜坡软弱地基路堤工程。因斜坡软弱地基的特殊性,易出现垮塌失稳、地基侧向变形过大等典型病害。本文通过文献阅读、工程调研,在全面地回顾、评述斜坡软弱地基路堤工程最新研究进展的基础上,运用精细化数值仿真技术,基于岩土工程计算力学软件P1axis和FLAC3D,依托室内土工离心模型试验及现场测试的研究成果,系统地研究了斜坡软弱地基路堤的变形和稳定性等工程特性,提出了兼顾“变形”与“稳定”的斜坡软弱地基路堤双指标设计体系,归纳总结了斜坡软弱地基路堤的工程处治对策。论文所取得的主要研究成果如下：(1)结合国内公路、铁路、岩土等行业规范,从成因、分布、工程特性等方面入手,较系统地比较了“斜坡软土”与一般“软土”的异同,明确了“斜坡软土”的概念,并尝试提出了“斜坡软土”相应的判别标准。(2)运用非线性有限元法,建立斜坡软弱地基在路堤自重荷载作用下的数值分析模型,模拟了路堤分步建造的施工力学行为,从土体变形和稳定安全性两方面进行研究,并结合土工离心模型试验成果,综合论证了表层软弱层、地面横坡对路基结构工程特性的影响。结果表明：斜坡软弱地基不能简单看成斜坡地基和软弱地基的等权重线性叠加；表层软弱层、地面横坡加剧了地基的侧向变形、竖向沉降,改变了潜在滑移面的形态,导致路堤结构稳定性降低,工程中应高度重视下坡脚处的侧向变形以及对表层软弱层的处理。(3)基于弹塑性平面应变有限单元法,建立了斜坡软弱地基在路堤荷载作用下的数值分析模型,真实模拟了路堤水平分层分步填筑的动态施工力学行为,获得普通水平地基、水平软弱地基、普通斜坡地基及斜坡软弱地基四种工况下地基的侧向变形与竖向沉降随路堤填筑施工的动态变化规律。引入地基变形系数,分析了地基侧向变形与竖向沉降之间的相互耦合、制约关系,奠定基于侧向变形控制的斜坡软弱地基路堤设计原则的理论基础,结合土工离心模型试验所获得的地基变形系数及位移场,讨论了打入桩与抗滑桩加固斜坡软弱地基路堤的机理。结果表明：引入无量纲化的地基变形系数,并通过其随路堤分层分步建造而变化的趋势,包括单调性、陡缓性、与1.0之间的大小关系等,可科学描述地基侧向变形与竖向沉降之间的相互耦合、制约关系,能有效指导工程对策选用；打入桩、抗滑桩加固斜坡软弱地基路堤机理不同,打入桩主要是控制斜坡软弱地基竖向沉降,同时可适当抑制侧向变形；抗滑桩主要是抑制侧向变形,对沉降控制作用有限。(4)运用非线性有限元法建立斜坡软弱地基在路堤自重荷载作用下的数值模型,探讨了软弱层特性各因素对斜坡软弱地基路堤变形的影响,通过正交试验设计,评价了软弱层特性各因素对变形影响的显著性。结果表明：软弱层土体模量、软弱层厚度是产生过大竖向沉降和侧向变形的决定性因素；地面横坡的存在,是加剧地基变形的重要因素；当软弱层位于地基顶面时,其对地基变形,尤其是侧向变形影响显著；软弱层特性各因素对侧向变形和竖向沉降的影响权重不一致；宜综合考虑软弱层特性多因素的影响,采取地基处理、侧向约束等工程对策限制变形。(5)因现行技术规范尚未明确定义斜坡软弱地基的概念及工程处治对策,或仅通过调整单一影响参数的试算方法尝试修正考虑地层坡度的稳定安全系数容许值。为准确获取斜坡软弱地基变形和路堤稳定性的内在联系,运用弹塑性有限元法,建立了斜坡软弱地基在路堤自重荷载作用下的数值模型,根据弹塑性变形所获的地基变形系数以及剪切强度折减法所获的稳定安全系数,结合渝怀铁路实际工点的现场测试成果,构建了兼顾“变形”与“稳定”的斜坡软弱地基路堤双指标设计体系,论证了该体系的科学性、可操作性,提出了该设计体系的实际运用步骤。结果表明：兼顾“变形”与“稳定”的斜坡软弱地基路堤双指标设计体系可更真实地反映路堤的稳定状态及变形发展趋势,有效指导工程设计及施工(6)鉴于在路堤下坡脚处采用钢筋混凝土抗滑桩可有效限制地基侧向变形,是斜坡软弱地基路堤的核心设计原则之一。采用三维快速拉格朗日有限差分法,经与室内土工离心模型试验成果对比、校核,建立了抗滑桩加固斜坡软弱地基路堤的精细化数值分析模型,研究了抗滑桩桩距、桩长、桩身弹性模量、桩身横截面尺寸及桩位等设计参数对其内力、变位的影响。结果表明：下坡脚处实施抗滑桩可显著约束斜坡软弱地基侧向变形；需综合考虑桩身受力、经济性、施工等影响因素以确定合理的桩距；桩身应深入滑移面以下,但随着桩身长度的增长,加固效果增长不明显；随着桩身弹性模量、桩身横截面尺寸的增加,抗滑桩的加固效果得到一定提高；抗滑桩宜设置在下坡侧路堤边坡的中部。(7)初步提出了斜坡软弱地基路堤工程处治的基本原则,并从提高地基整体抗变形能力、提高地基抗失稳能力、强化路堤本体、采用桩网(桩板)结构等新型结构性路堤以及加强防排水等方面,系统归纳了斜坡软弱地基路堤的主要工程处治对策,明确了不同处治措施的适用范围、适用条件。
[Abstract]:Chinese vast, widely distributed in Hilly and mountainous areas, transportation infrastructure construction frequently encountered the slope of embankment on soft foundation engineering. Because of the particularity of slope weak foundation, prone to collapse instability, the lateral deformation of the soil is too large. Typical disease through literature reading, engineering research, in a comprehensive review, based on the latest research progress on the slope of embankment on soft foundation engineering, using numerical simulation technology of fine, computational mechanics software P1axis and FLAC3D geotechnical engineering based on indoor test and field based on the geotechnical centrifuge model test research results, systematically studied the characteristics of slope deformation and stability of embankment on soft foundation engineering, puts forward the double index system design consideration the deformation and stability of embankment on soft foundation of slope, the slope of embankment on soft foundation engineering treatment measures are summarized. The main research papers made The results are as follows: (1) combined with the domestic highway, railway, geotechnical and other industry standards, from the origin, distribution, engineering properties and other aspects, and systematically compares the "slope soft soil" and "soft", defined the concept of "slope soft soil", and tries to put forward the relevant criteria for soft soil on the slope ". (2) using nonlinear finite element method, a numerical slope weak foundation in embankment under self weight load analysis model, simulation of the construction mechanics behavior of embankment construction step by step, from the two aspects of soil deformation and stability safety research, combined with the results of geotechnical centrifuge model test comprehensive, demonstrates the weak surface layer effect, ground slope characteristics of subgrade engineering structure. The results show that the slope soft foundation slope foundation and not simply as a weak foundation and weighted linear superposition; weak surface layer, ground slope increased The foundation of the lateral displacement, vertical settlement, change the shape of the potential slip plane, which leads to the decrease of embankment structure stability, should attach great importance to the downhill at the foot of the lateral deformation and processing of weak surface layer in engineering. (3) the elastic-plastic plane strain finite element method based on the established numerical analysis model of slope weak foundation in under embankment load, simulate the dynamic construction mechanical behavior of embankment filling level step by step, general level of foundation level, weak foundation, common slope foundation and slope weak foundation lateral foundation under four conditions of deformation and vertical settlement changes with the embankment construction. The subgrade deformation analysis of foundation the lateral coupling deformation and vertical settlement of the relationship between, lay a theoretical foundation for controlling the lateral deformation of the slope of embankment on soft foundation design based on the principle of, The foundation deformation coefficient and displacement field of geotechnical centrifuge model tests of the mechanism of pile and anti slide pile reinforced slope embankment on soft foundation is discussed. The results show that the dimensionless deformation of foundation coefficient varies with embankment and through its hierarchical construction process step trend, including monotonicity, steep slow, 1 and the size of the relationship between science, can describe the lateral deformation of the soil and the vertical settlement of the coupling between, restricted, can effectively guide the selection of engineering measures; driven pile, piles reinforced slope embankment mechanism with driven pile is mainly to control the slope soft foundation settlement, at the same time may be appropriate to inhibit lateral deformation anti slide pile; mainly inhibit lateral deformation, on the control of settlement is limited. (4) is used to establish the numerical model of slope soft foundation under embankment load under the action of nonlinear finite element method To investigate the effect of various factors, the weak layer characteristics of embankment on soft foundation of slope deformation, through the orthogonal experimental design, evaluation of various factors of weak layer characteristics on the significant effect of deformation. The results show that the soft soil layer modulus, thickness of weak layer is a decisive factor in the vertical settlement and lateral deformation of the ground slope; there is an important factor of subgrade deformation; when the soft layer is located in the top surface of foundation, the foundation deformation, especially the lateral deformation effect; weak layer characteristics on the influence factors of the lateral deformation and settlement of the weight is not consistent; should consider the influence of multi factors of weak layer characteristics, take the foundation treatment. The lateral constraint measures limit deformation. (5) because of the concept and project of the current technical specification is not yet clear definition of slope soft foundation treatment measures, or only by adjusting the parameters of the single effect This method attempts to consider correction of allowable value of stability coefficient of slope of formation. As the inner link to accurately obtain the slope soft foundation deformation and stability of embankment, with the elastic-plastic finite element method, a numerical model of slope weak foundation in embankment under gravity load, according to the elastic-plastic deformation of the foundation deformation and shear coefficient strength reduction by the safety factor, combined with the actual test results of the Chongqing Huaihua railway project, construction of a dual index system design taking into account the deformation and stability of embankment on soft foundation of slope, proof of the scientific nature of the system, operation, put forward practical steps of the design system. Show that the double index system design both "deformation" and "stability" of the slope of embankment on soft foundation can reflect the stability of embankment deformation and development trend, effectively Guide the engineering design and construction (6) given in the downhill at the foot of embankment reinforced concrete can effectively limit the lateral deformation of foundation piles, is one of the core principles of design of slope of embankment on soft foundation. Using Lagrange finite difference method, and the indoor geotechnical centrifuge model test results, calculation, analysis model is established fine numerical piles reinforced slope soft foundation embankment, the anti slide pile spacing, pile length, pile modulus, pile cross section size and pile design parameters such as the internal force, displacement effect. The results show that the downhill at the foot of implementation can significantly constrain the lateral deformation of slope weak foundation anti slide pile; axial forces, the need to consider the economic factors affecting the construction of pile, etc. to determine the reasonable pile spacing; pile should be deep slip surface below, but with the increase of the length of the pile, the reinforcement effect of the growth is not obvious With the elastic modulus of pile; pile, increase the size of cross section, anti slide pile reinforcement effect can be improved; the anti should be arranged in the middle of the downhill side of the slope of embankment pile. (7) proposed the basic principles of slope embankment engineering soft foundation treatment, and improve the overall ability to resist deformation from the ground. The foundation to improve the anti instability capability, strengthen the embankment, the pile net (plate pile) structure of new embankment and strengthen the anti structural drainage system, summarizes the main engineering slope of embankment on soft foundation treatment measures, clear the applicable scope of different treatment measures of the applicable conditions.

【学位授予单位】：西南交通大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U416.12

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