Research on the critical strength of the initial structure of the uncemented coarse-grained soil
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摘要:
无论是原状土还是重塑土均存在初始结构性，土体初始结构所抵抗的剪应力为土体结构强度。为了研究无胶结粗粒土初始结构强度，定义了粗粒土剪切过程中初始结构变化点特征，并根据大于20 mm粗颗粒含量将粗粒土划分为4种结构类型，采用可视化直剪仪对不同结构特征的粗粒土进行直剪试验，通过剪切过程中粗粒土平面孔隙比、配位数、概率熵等3种初始结构指标的数值大小及变化趋势，来确定不同初始结构的粗粒土结构临界强度。结果表明：不同初始结构类型粗粒土在相同正应力、相同颗粒种类的情况下，其抗剪强度大小与结构强度占比大小的排序一致，表明了颗粒结构强度在抵抗剪应力的整个过程中起到了重要作用。4种初始结构类型粗粒土平均结构强度占比为36.27%，即结构强度占峰值抗剪强度的36.27%，其中排列接触结构的结构强度占比最高，为36.62%，其次为镶嵌结构36.61%，悬浮密实结构35.99%，叠置结构的结构强度占比最低，为35.87%。
Abstract:Both the undisturbed soil and remolded soil have initial structural properties, and the shear stress resisted by the initial structure of the soil is the structural strength of the soil. In order to study the initial structural strength of the uncemented coarse-grained soil, this paper defines the characteristics of the initial structural change points of the coarse-grained soil during the shearing process, and divides the coarse-grained soil into four structural types according to the content of the coarse-grained soils greater than 20 mm. Visual direct shear instrument direct shear tests are carried out on the coarse-grained soils with different structural characteristics, and the critical strength of the coarse-grained soils with different initial structures is determined through the numerical value and the change trend of the initial structure indexes of the coarse-grained soils during the shearing process. The results show that the shear strength of the coarse-grained soils with different initial structure types under the same normal stress and the same particle type are in the same order as the proportion of the structural strength, indicating that the particle structure strength plays a role in the whole process of the resisting shear stress. The average structural strength of the four initial structure types of the coarse-grained soils accountes for 36.27%, that is, the structural strength accountes for 36.27% of the peak shear strength. The arranged contact structure has the highest structural strength at 36.62%, followed by the mosaic structure 36.61%. The suspended dense structure is 35.99%, and the superimposed structure has the lowest proportion of the structural strength, which is 35.87%.
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Key words:
- coarse-grained soil /
- shear strength /
- initial structure /
- structural strength /
- structure type
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表 1 试样配比信息
Table 1. Sample ratio information
法向荷载
/kPaP20/% 叠置结构 镶嵌结构 排列接触结构 悬浮密实结构 50 80 60 40 15 100 80 60 40 15 150 80 60 40 15 200 80 60 40 15 
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表 2 初始结构信息提取结果
Table 2. Initial structure information extraction results
正应力/ kPa P20/% 平面孔隙率/% 概率熵 配位数 50 15 20.16 0.975 4.67 50 40 17.72 0.958 4.12 50 60 18.36 0.953 4.26 50 80 16.92 0.941 4.06 100 15 19.52 0.969 4.71 100 40 17.58 0.951 4.29 100 60 15.96 0.952 4.19 100 80 17.93 0.943 4.03 150 15 18.39 0.972 4.82 150 40 16.56 0.961 4.32 150 60 15.77 0.958 4.31 150 80 15.60 0.946 4.05 200 15 16.72 0.970 4.72 200 40 14.60 0.953 4.34 200 60 14.97 0.959 4.29 200 80 15.52 0.947 4.07
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表 3 区间细化的各类型初始结构指标信息
Table 3. Initial structure index information for each type of interval refinement
剪切位移/mm 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 悬浮密实结构 配位数 4.731 4.731 4.735 4.736 4.736 4.736 4.737 4.737 4.737 4.738 孔隙比 18.673 18.674 18.686 18.689 18.689 18.690 18.690 18.691 18.691 18.692 概率熵 0.9713 0.9714 0.9715 0.9717 0.9717 0.9716 0.9718 0.9718 0.9719 0.9719 排列接触结构 配位数 4.268 4.268 4.268 4.268 4.269 4.269 4.271 4.270 4.271 4.272 孔隙比 16.611 16.612 16.612 16.613 16.613 16.614 16.618 16.622 16.623 16.624 概率熵 0.9557 0.9557 0.9557 0.9557 0.9558 0.9559 0.9560 0.9560 0.9560 0.9560 镶嵌结构 配位数 4.263 4.263 4.263 4.264 4.264 4.264 4.265 4.266 4.266 4.267 孔隙比 16.255 16.256 16.258 16.258 16.260 16.260 16.269 16.271 16.272 16.273 概率熵 0.9556 0.9556 0.9557 0.9557 0.9559 0.9560 0.9564 0.9567 0.9568 0.9570 叠置结构 配位数 4.052 4.053 4.053 4.053 4.054 4.055 4.055 4.056 4.056 4.056 孔隙比 16.482 16.483 16.484 16.485 16.489 16.490 16.492 16.493 16.495 16.498 概率熵 0.9443 0.9443 0.9444 0.9444 0.9446 0.9448 0.9448 0.9448 0.9449 0.9450
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表 4 各类型初始结构强度及结构强度占比
Table 4. Initial structural strength of each type and the proportion of structural strength
初始结构
类型法向应力
/kPa结构强度
/kPa峰值抗剪
强度/kPa结构强度
占比/%结构强度占比
平均值/%悬浮密实结构 50 124.73 342.95 36.37 35.99 100 192.97 531.75 36.29 150 273.46 759.39 36.01 200 308.10 873.55 35.27 排列接触结构 50 135.96 367.86 36.96 36.62 100 231.33 623.20 37.12 150 326.55 899.83 36.29 200 383.91 1063.16 36.11 镶嵌
结构50 130.22 347.91 37.43 36.61 100 225.58 606.23 37.21 150 297.11 823.94 36.06 200 348.41 974.03 35.77 叠置
结构50 122.46 338.57 36.17 35.87 100 196.80 548.95 35.85 150 255.85 730.36 35.03 200 280.93 771.14 36.43
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