A study of shear strength characteristics and estimation model of limestone under different weathering degrees
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摘要:
工程上常见的灰岩在不同风化程度下的抗剪强度特性鲜有研究，也没有快速评估灰岩抗剪强度的数学模型，不能满足大量灰岩工程灾害防治的需要。为探究风化程度对灰岩抗剪强度特性的影响规律，试验选取现场新鲜灰岩试样，通过开展室内风化模拟试验制备不同风化程度的岩样，进行室内岩石强度剪切试验，探究灰岩剪切应力-剪切位移关系曲线的变化规律和抗剪强度的劣化规律。通过建立风化程度下灰岩抗剪强度估算模型，揭示风化程度与抗剪强度的定量化关系。试验结果表明：随着风化程度的增加，灰岩抗剪强度和残余抗剪强度均呈现减小的趋势，但残余抗剪强度比抗剪强度劣化更严重，且劣化速度更快；灰岩随着风化程度的增加，其黏聚力c及内摩擦角φ均越来越小，两者劣化趋势相似；利用波速比量化风化程度，建立起风化作用下灰岩抗剪强度估算模型，通过简单测量计算岩石的波速比，即可快速评估岩石的抗剪强度特性。研究结果可为灰岩工程抗剪强度特性的评估提供更加简便易行的方法。
Abstract:The shear strength characteristics of common limestone in engineering under different weathering degrees were seldom examined, and there is no mathematical model for rapid evaluation of the shear strength of limestone, which cannot meet the needs of prevention and control of a large number of limestone engineering disasters. In order to explore the influence of weathering degree on the shear strength characteristics of limestone, the fresh limestone samples are selected in the test. The rock samples with different weathering degrees are prepared by indoor weathering simulation test. The indoor rock strength shear test is carried out to explore the variation law of the shear stress-shear displacement curve of limestone and the deterioration law of shear strength and its parameters. The quantitative relationship between the weathering degree and shear strength is revealed by establishing the shear strength estimation model of limestone under weathering degree. The test results show that with the increasing weathering degree, the shear strength and residual shear strength of limestone show a decreasing trend, but the residual shear strength is worse than the shear strength, and the deterioration rate is faster. With the increasing weathering degree, the cohesion c and internal friction angle φ of limestone are getting smaller and smaller, and the deterioration trend is similar. Using the wave velocity ratio to quantify the weathering degree, the shear strength estimation model of limestone under weathering is established. The shear strength characteristics of rock can be quickly evaluated by simply measuring and calculating the wave velocity ratio of rock. The research results can provide a more simple and feasible method for evaluating the shear strength characteristics of limestone engineering.
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Key words:
- limestone /
- weathering degree /
- shear strength /
- estimation model
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表 1 灰岩风化试验方案
Table 1. Limestone weathering test plan
序号 组号 试样编号 干湿循环
试验次数1 第1组 1—4 0 2 第2组 5—8 10 3 第3组 9—12 20 4 第4组 13—16 30 5 第5组 17—20 40 
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表 2 风化作用下灰岩波速测试及风化程度判定
Table 2. Limestone wave speed test and weathering degree judgment under weathering
试样
编号岩石波速
值Vud/（m·s−1）岩石波
速比kv风化
程度试样
编号岩石波速值
Vud/（m·s−1）岩石波
速比kv风化
程度1 6572.43 1 未风化 11 5419.06 0.84 微风化 2 6376.11 1 未风化 12 5611.26 0.86 微风化 3 6453.32 1 未风化 13 4901.42 0.75 弱风化 4 6534.22 1 未风化 14 4947.34 0.77 弱风化 5 6243.81 0.95 未风化 15 5289.72 0.8 微风化 6 5613.35 0.87 微风化 16 4949.24 0.76 弱风化 7 5878.76 0.93 未风化 17 4586.44 0.71 弱风化 8 5833.17 0.91 未风化 18 4600.51 0.72 弱风化 9 5470.51 0.82 微风化 19 4779.38 0.74 弱风化 10 5485.59 0.86 微风化 20 4843.51 0.74 弱风化 注：现有《公路工程地质勘查规范JTGC 20—2011》规范给出了岩石风化程度与波速比之间的关系：新鲜岩石：0.9~1.0；微风化：0.8~0.9；弱风化：0.6~0.8；强风化：0.4~0.6；全风化：<0.4。
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表 3 不同风化程度灰岩的宏细观特征
Table 3. Macro and mesoscopic characteristics of limestone with different weathering degrees
试样编号 风化程度 宏观特征 细观特征 1 未
风
化表面未见风化痕迹，岩石表面颜色较浅，岩石表面颜色呈现出原岩本身颜色且表面光滑 岩石表面未见风化裂隙，原生构造结构清晰，色调明亮 6 微
风
化表面偶见风化痕迹，岩石表面颜色略变深呈褐色，未见明显风化裂隙 岩石表面未见裂隙，原生构造结构清晰，色调明亮，表面可见部分明亮颗粒 10 微
风
化表面少量风化痕迹，岩石表面可见风化晕，部分表面颜色略有变深，表面可见部分微小裂隙 岩石表面裂隙偶见，构造清晰，色调较为明亮，表面明亮颗粒减少 16 弱
风
化表面可见风化痕迹，部分表面颜色略有变深，表面可见部分裂隙 岩石表面可见明显裂纹，构造较清晰，色调较暗淡 20 弱
风
化表面有风化痕迹，大部分变色，颜色变化较为明显，岩石表面出现部分锈蚀现象，表面可见部分贯穿裂隙，裂隙分布范围较广 岩石表面裂隙较为发育，岩石表面出现较大裂隙，裂隙宽度约为0.1 mm，色调较为暗淡
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表 4 抗剪强度与残余抗剪强度数据表
Table 4. Data of shear strength and residual shear strength
风化
程度试样
编号法向应
力/MPa抗剪强
度/MPa残余抗
剪强度/
MPa抗剪强
度减量
百分比/%残余抗剪
强度减量
百分比/%未
风
化1 1 2.81 2.01 / / 2 2 3.51 2.55 / / 3 3 3.92 2.48 / / 4 4 5.25 3.53 / / 微
风
化6 1 2.56 1.86 8.90 7.46 9 2 3.26 2.06 7.12 19.22 10 3 3.56 2.20 9.18 11.29 11 4 4.82 3.01 8.19 14.73 弱
风
化17 1 2.35 1.31 16.37 34.83 18 2 3.02 1.62 13.96 36.47 19 3 3.25 1.61 17.09 35.08 20 4 4.35 2.48 17.14 29.75
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表 5 不同风化程度下灰岩力学参数建议值
Table 5. Recommended values of the mechanical parameters of limestone under different weathering degrees
序号 风化
程度内摩擦角
φ/（°）黏聚力
c/MPaφ减量
百分比/%c减量
百分比/%1 未风化 37.57 1.95 / / 2 微风化 35.33 1.77 5.96 9.23 3 弱风化 31.47 1.67 16.24 14.36
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