大前石岭隧道边坡碎石土强度试验研究

发布时间：2018-04-28 03:06

本文选题：碎石土 + 大型直剪试验　；参考：《中国地质大学》2015年硕士论文

【摘要】：伴随着东北老工业基地振兴计划的实施,我国对当地基础设施的投入力度不断加大,东北地区铁路、公路及桥梁等基础工程建设蓬勃发展。随着大量的工程建设,人工高边坡问题逐渐突出,而各种边坡的失稳往往都是由于剪切破坏引发的,要对其进行稳定性分析与治理工程设计,准确的把握岩土体强度特性是关键。因此,针对岩土体的物理力学性质的研究,已成为边坡稳定性分析与灾害防治中的一项重要任务。岩土体抗剪强度指标是进行斜坡稳定性评价的重要力学参数,其取值直接决定稳定性分析的结果,通常通过试验的手段来获取(包括室内试验和现场原位试验),然后对所得的试验数据采用回归统计分析以获得其抗剪强度参数指标,从而进行斜坡稳定性评价。近期动工兴建的田师府-桓仁铁路大前石岭隧道进口段开挖形成人工边坡,坡体物质组成以碎石土、块石土为主,边坡一旦失稳将严重威胁铁路运营及人民的生命财产安全。碎石土的物理力学性质既不同于通常的土类,也区别于一般的岩体,而是介于土体和岩体之间的一种特殊的非连续的高度非均质的地质体。由于大前石岭隧道边坡体土中粗颗粒含量较多,当粗颗粒组成不同时,其性质差别甚大,进行常规的直剪试验已不能满足对其力学性质的完整研究。为此,本文以大前石岭隧道边坡碎石土为研究对象,通过野外现场调查取样、室内常规物理力学试验及室内大型直剪试验对该碎石土的基本物理性质、剪切特性、抗剪强度参数变化规律、粒度分形特性等方面进行研究,可为该边坡后期的稳定性分析和防治提供可靠的岩土参数。本文主要开展的工作及取得的成果如下：(1)基本物理性质研究。通过野外现场测试和室内试验确定了大前石岭隧道边坡碎石土的天然密度、天然含水率及其颗粒组成情况等基本物理性质参数。(2)抗剪强度特性研究。以室内大型直剪试验为主,常规直剪试验为辅,对大前石岭隧道边坡碎石土按不同含石量、不同含水率、不同碎石尺寸进行重塑样配制,配制出三组不同含石量(粗粒含量分别为30%,50%,68.53%)、三组不同含水率(含水率分别为9.05%,12.50%,饱和)及三组不同碎石尺寸(三个区间粒径为60～40mm,40～20mm,20～5mm)的碎石土重塑试样,分别进行大型直剪试验和三种不同含水率下的常规直剪试验,建立了其相应条件下的抗剪强度库伦拟合公式。(3)抗剪强度参数与含石量变化相关性研究。根据三组不同粗粒含量重塑试样的大型直剪试验结果,分析了抗剪强度、强度参数、应力-应变曲线随着粗粒含量变化的作用规律。研究发现,粗粒含量在很大程度上影响着碎石土的抗剪强度。随着粗粒含量的增大,抗剪强度增大；内摩擦角随着粗粒含量的增加而增大,在粗粒含量为30%-50%之间增幅较快,粗粒含量超过50%后,增幅较慢而呈现逐渐稳定的趋势；粘聚力随着粗粒含量的增大先略微下降后急剧上升,在粗粒含量达到50%时最低,而后急剧升高。不同粗粒含量下碎石土重塑样应力-应变曲线均没有出现明显的峰值强度,表现为弹性变形阶段、屈服阶段和应变硬化阶段三个阶段。随着粗粒含量的增加,屈服阶段愈为明显；在同一法向应力下,粗粒含量高的碎石土试样应变硬化程度明显比粗粒含量低的碎石土试样高。碎石土变形破坏机制在很大程度上受到其内部粗粒含量的影响。(4)抗剪强度参数与含水率变化相关性研究。根据三组不同含水率重塑试样的大型直剪试验结果,分析了抗剪强度、强度参数、应力-应变曲线随着含水率变化的作用规律。研究发现,抗剪强度随着含水率的增大而降低；内摩擦角随着含水率的增大而降低；粘聚力对含水率变化的敏感性比内摩擦角高,随着含水率的增大先略微增大后急剧降低；含水率由9.05%上升为12.50%时,粘聚力略有上升,而后粘聚力随含水率的升高急剧下降。不同含水率下碎石土重塑样应力-应变曲线均没有出现明显的峰值强度,表现为弹性变形阶段、屈服阶段和应变硬化阶段三个阶段。随着含水率的增大,屈服阶段而表现的愈不明显。在同一法向应力下,含水率低的试样应变硬化程度明显比含水率高的试样高。(5)大型直剪试验与常规直剪试验对比研究。三组不同含水率下大型直剪与室内常规直剪重塑样的试验结果对比分析发现,粘聚力和内摩擦角在二种不同的试验方式下的变化规律基本相同,大型剪切试验得出的粘聚力和内摩擦角均高于室内常规小型剪切试验,大型直剪试验得到的抗剪强度参数结果更贴近碎石土的实际力学性质。(6)碎石土粒度分形特性研究。引入分形理论,采用颗粒质量-粒径分布分形模型,对含石量均为50%的重塑试样进行了分维数的计算。计算表明,在粗粒含量相同的情况下,随着碎石尺寸的相对增大,分维数增大；分维数越大,其颗粒粒度分布越不均匀；分维数越小,其颗粒粒度分布越均匀。(7)抗剪强度参数与碎石尺寸相关性研究。研究表明,在粗粒含量相同时,抗剪强度随着碎石尺寸的相对增大而增大,抗剪强度增大的幅度也随着碎石尺寸的相对增大而增大；内摩擦角随着碎石土内碎石相对尺寸的增大而增大；而粘聚力呈现相反的趋势,随着碎石相对尺寸的增大而降低。不同碎石尺寸下的碎石土重塑样应力-应变曲线均没有出现明显的峰值强度,表现为弹性变形阶段、屈服阶段和应变硬化阶段三个阶段。在大粒径区间组及中粒径区间组时,应力-应变曲线呈现为应变硬化型,而小粒径区间组在高法向应力时,逐渐呈现出弱应变软化型。随着碎石相对尺寸的增大,剪应力达到峰值强度前的屈服阶段历时愈长。(8)抗剪强度参数与粒径分形维数相关性研究。研究发现,碎石土抗剪强度和粒度分维数有一定程度的相关性。粘聚力随着分形维数的增大而减小,而内摩擦角呈现相反的趋势,随着分形维数的增大而增大,粘聚力和内摩擦角均与粒度分维数近似呈现抛物线函数关系。
[Abstract]:With the implementation of the revitalization plan of the northeast old industrial base, the investment in the local infrastructure is increasing, and the construction of the railway, highway and Bridge in the northeast is flourishing. With the construction of a large number of projects, the problem of artificial high slope is becoming more and more prominent, and the instability of all kinds of slopes is often caused by shear failure. In order to carry on the stability analysis and control engineering design, it is the key to accurately grasp the strength characteristics of rock and soil soil. Therefore, the study of the physical and mechanical properties of rock and soil has become an important task in the analysis of slope stability and disaster prevention and control. The shear strength index of rock and soil is an important mechanics for the evaluation of slope stability. Parameters, which directly determine the results of stability analysis, are usually obtained by means of experiments (including indoor and in-situ test), and then regression statistical analysis is used to obtain the parameters of the shear strength parameters for the obtained experimental data. Thus the slope stability is evaluated. The recent construction of Tian Shi Fu Huanren Railway The entrance section of the great front Shiling tunnel is excavated to form an artificial slope. The material of the slope body is composed of crushed rock soil and block rock. Once the slope is unstable, it will seriously threaten the railway operation and the safety of the people's life and property. The physical and mechanical properties of the gravel soil are different from the ordinary soil, but also different from the ordinary rock mass, but between the soil and the rock mass. A special discontinuous highly heterogeneous geological body. Due to the large amount of coarse particles in the somatic soil of the big front Shiling tunnel slope, the nature of its properties is very different when the composition of coarse particles is different. The conventional direct shear test can not satisfy the complete study of its mechanical properties. Therefore, this paper takes the lithotripsy of the big front Shiling tunnel slope as research. Through field investigation sampling, indoor physical and mechanical test and indoor large direct shear test, the basic physical properties, shear characteristics, changing law of shear strength parameters and fractal characteristics of the shear strength are studied, which can provide reliable rock and soil parameters for the stability analysis and prevention and control of the slope in the later period. The main work and achievements are as follows: (1) basic physical properties study. Through field test and indoor test, the natural density, natural water content and particle composition of the great front Shiling tunnel slope are determined. (2) study on the shear strength characteristics of the rock soil. (2) the indoor large direct shear test As a supplement to the conventional direct shear test, three groups of different rock content (30%, 50%, 68.53%) were prepared from the lithotripsy soil of the slope of the big front Shiling tunnel, with different content of stone, different water content and different size of gravel, and three different water content (water content was 9.05%, 12.50%, saturation) and three different lithotripsy sizes (water content was 9.05%, 12.50%, saturated). The remolded specimens of gravel soil with three intervals of 60 to 40mm, 40 to 20mm and 20 to 5mm are remolded specimens for large direct shear tests and three kinds of conventional direct shear tests under different water content. The fitting formula of the shear strength under the corresponding shear strength under the corresponding conditions is established. (3) Study on the correlation between the shear strength parameters and the variation of the rock content. According to three groups of different coarse particles The effect of shear strength, strength parameter, stress strain curve with the change of coarse grain content is analyzed. It is found that the content of coarse grain affects the shear strength of the gravel soil to a great extent. With the increase of coarse grain content, the shear strength increases, and the internal friction angle increases with the content of coarse grain. When the coarse grain content is 30%-50%, the increase of the coarse grain content is more than 50%, the increase of the coarse grain content is slower and the trend is steady. The cohesive force increases slightly with the increase of the coarse grain content, and then rises sharply at 50% when the coarse grain content is reached, then the stress strain of the crushed stone soil under different coarse grain content is remolded. There is no obvious peak intensity in the curve, which shows three stages of elastic deformation, yield stage and strain hardening stage. With the increase of coarse grain content, the more obvious the yield stage is. Under the same normal stress, the strain hardening range of the rock specimen with high coarse grain content is obviously higher than that of the gravel soil with low content of coarse grain. The deformation and failure mechanism of rock and soil is greatly influenced by its internal coarse grain content. (4) study on the correlation between the shear strength parameters and the change of water content. According to the large direct shear test results of the remolded specimens of three groups of different water content, the effect of the shear strength, strength parameters and stress strain curves with the change of water content is analyzed. It is found that the shear strength decreases with the increase of water content, and the internal friction angle decreases with the increase of water content, and the sensitivity of cohesion to the change of water content is higher than that of the internal friction angle. With the increase of water content, the cohesion is slightly increased after a slight increase. When the water content rises from 9.05% to 12.50%, the cohesive force increases slightly, and then the cohesion is followed with the cohesive force. There is no obvious peak intensity in the stress strain curve of the remolded samples of the crushed rock and soil under the different water content, which shows the three stages of the elastic deformation stage, the yield stage and the strain hardening stage. With the increase of water content, the less obvious the yield stage is. Under the same normal stress, the low water content test The strain hardening degree of sample is higher than that of the sample with high water content. (5) a comparative study of the large direct shear test and the conventional direct shear test. The comparison and analysis of the experimental results of the three groups of large direct shear and indoor conventional direct shear reshaping found that the cohesive force and the internal friction angle are basically the same under the two different test modes. The cohesive force and internal friction angle obtained by the type shear test are higher than that in the conventional small shear test. The results of the shear strength parameters obtained by the large direct shear test are more close to the actual mechanical properties of the crushed rock soil. (6) the fractal characteristics of the gravel soil particle size are studied. The fractal theory is introduced and the particle mass particle size distribution fractal model is applied to the rock content of 50. The fractal dimension calculation shows that the fractal dimension increases with the relative increase of the size of the crushed stone in the case of the same coarse grain content; the larger the fractal dimension, the more uneven the particle size distribution is, the smaller the fractal dimension is, the more uniform the particle size distribution is. (7) research on the correlation between the shear strength parameters and the size of the crushed stone. It is shown that the shear strength increases with the relative increase of the size of the gravel, and the increase of the shear strength increases with the relative increase of the size of the crushed stone, and the internal friction angle increases with the increase of the relative size of the crushed stone in the gravel soil. The stress strain curves of lithotripsy soils under different macadam sizes have no obvious peak intensity, showing three stages of elastic deformation, yield stage and strain hardening stage. In the large particle size interval group and the medium size interval group, the stress-strain curve presents strain hardening type, while the small size interval group is in the area. With the higher normal stress, the weak strain softening type is gradually presented. With the increase of the relative size of the crushed stone, the longer the yield stage before the shear stress reaches the peak strength. (8) the correlation between the shear strength parameters and the fractal dimension of the particle size. The fractal dimension increases and the internal friction angle presents the opposite trend, which increases with the increase of the fractal dimension. The cohesive force and the internal friction angle are approximately parabolic function relation with the particle size fractal dimension.

【学位授予单位】：中国地质大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U456

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