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Application of Catastrophe Progression Method in the Stability Evaluation of Subgrade in Permafrost Area—A Case Study of G213 National Highway in Qilian, Qinghai Province
DOI: 10.12677/HJCE.2022.116090, PDF, HTML, XML, 下载: 94  浏览: 125  科研立项经费支持

Abstract: The stability of highway subgrade in permafrost areas has always been a hot topic of theoretical and practical research. In this paper, the catastrophe progression method is proposed to evaluate the subgrade stability of the G213 National Highway in Qilian, Qinghai Province. Based on 39 sets of geotechnical test data, starting from 7 bottom control indexes such as cohesion, internal friction angle, compressibility, natural density, void ratio, water content, and permeability coefficient, we comprehensively consider the impact of each control index on the geotechnical properties of geotechnical engineering. The results show that the catastrophe progression method can represent the engineering property level. The mechanical properties, physical properties, and permeability coefficient of soil mass are sensitive to different grades of engineering properties of soil mass. The mechanical properties and physical properties of soil have a great influence on its engineering property grade, while the permeability coefficient has little influence.

1. 引言

2. 突变级数评价法的基本原理

2.1. 评价指标的无量纲化

${{x}^{\prime }}_{i}=\frac{{x}_{i}-{x}_{\mathrm{min}}}{{x}_{\mathrm{max}}-{x}_{\mathrm{min}}}$ (1)

${{x}^{″}}_{i}=\frac{{x}_{\mathrm{max}}-{x}_{i}}{{x}_{\mathrm{max}}-{x}_{\mathrm{min}}}$ (2)

2.2. 归一公式即突变级数的推导

2.3. 突变级数的计算

3. 研究区概况及突变级数的应用

G213国道是在中国西北、西南地区的一条国道，经过内蒙古、甘肃、青海、四川、云南5个省份，其中青海省祁连段长度为333.4公里。行政区划位于青海省海西蒙古族藏族自治州及海北藏族自治州管辖，其中北部为祁连县、南部为天峻县及刚察县，位于青海湖西北部、柴达木盆地东缘。最高海拨5076 m，最低海拨2356 m，相对高差近2700 m，平均海拨4000 m以上。

3.1. 评价指标的选定

Table 1. Summary of geotechnical test data and results

Figure 1. Distribution of sampling points

Figure 2. Index system of frozen soil geological evaluation model

Table 2. Dimensionless treatment results of bottom index

3.2. 突变级数的计算

${x}_{c1}={\left(0.279\right)}^{1/2}=0.528$${x}_{c2}={\left(0.607\right)}^{1/3}=0.846$${x}_{c3}={\left(0.535\right)}^{1/4}=0.855$，含水率、密度和孔隙比三组数据直接可以通过相关公式计算得到，按照“互补”原则计算上层数据，得到 ${B}_{1}=\left(0.528+0.846+0.855\right)/3=0.743$

${x}_{c4}={\left(0.106\right)}^{1/2}=0.325$${x}_{c5}={\left(0.114\right)}^{1/3}=0.485$${x}_{c6}={\left(0.295\right)}^{1/4}=0.737$，压缩模量、黏聚力和内摩擦角三组数据，按照“互补”原则计算上层数据，得到： ${B}_{2}=\left(0.325+0.485+0.737\right)/3=0.516$

Table 3. Total catastrophe level of frozen soil engineering geological model

3.3. 结果分析

Figure 3. Interval statistics of total catastrophe series of frozen soil sampling points

Figure 4. Relationship between catastrophe progression and control index of frozen soil

4. 结论

1) 本文引入了一种多年冻土区公路路基稳定性评判方法——突变级数法，该方法由模糊数学引出，避开了对指标采用“权重”的主观性，又权衡了各评判指标的相对重要性，从岩土体力学性质、物理性质和渗透性三个方面出发，以黏聚力、内摩擦角、压缩系数、密度、含水率、孔隙比、渗透系数6个控制性定量指标为出发点，由归一化公式对目标进行无量纲化处理，较为综合地反映了各类因素对岩土体工程地质的特性评价，减少了人为赋值的干扰。

2) 突变级数的大小可以表示岩土体的工程性质等级，岩土体各控制变量对岩土体工程性质敏感程度不同，岩土体的力学性质和物理性质对岩土体的工程性质影响较大，对其渗透系数影响较小，突变级数法的岩土体工程地质评价方法结果准确，具有广泛的使用前景和良好的实用价值。

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