Effect factors analysis and characteristic of freeze-thaw deformation of fracture rock
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摘要: 高寒、高海拔地区由于反复冻融导致的岩体变形破坏，对区内工程建设有重大影响。为研究不同裂隙条件下岩体循环冻融特性，在汶马高速沿线选择具有代表性的千枚岩和砂岩，制备了不同裂隙条件（长度、张开度、裂隙组数）试样，在干燥和饱水两种状态下分别进行大温差（-20℃到20℃）循环冻融（50次）试验。试验揭示了饱水裂隙岩样冻融变形过程：冻缩→冻胀→冻缩（冻结阶段）→融胀→融缩→融胀（融化阶段），干燥裂隙岩样冻融变形过程：冻缩（冻结阶段）→融胀（融化阶段）。进一步，选择冻胀量εd为指标，分析了两类岩样冻融循环次数与εd的关系，揭示了裂隙长度、宽度和组数对εr的影响规律；选择残余变形量εr为指标，揭示了千枚岩和砂岩试样在饱水条件下εr随εd的增加规律，获得了εd与εr间的定量关系；分析了干燥和饱水试样单轴抗压强度随冻融循环次数增加而减小规律，确定了冻融次数与试样劣化间的线性关系。最后，初步讨论了饱水条件、岩性和裂隙条件对岩体冻融循环变形的影响机制。Abstract: In the cold and high-altitude regions of Sichuan Provence, the rock failure caused by freeze-thaw deformation has a significant impact on projects. In order to study the cyclic freeze-thaw characteristics of rock mass under different fracture conditions, the phyllite and sandstone were taken from this area. The rock samples with different joint lengths, opening, number of joints were conducted with 50 cycles of freeze-thaw tests under ±20℃. The test results showed that the saturated rock had process of freeze contract→freeze expand→freeze contract→thaw expand→thaw contract→thaw expand. The dry rock had process of freeze contract→melt expansion. The relationship between freeze-thaw cycle times and εd was studied. The length of joint, opening and number of joints had an influence on freeze-thaw deformation of dry sample. Select the residual deformation εr as an index to study the increasing of εr with increasing of εd for phyllite and sandstone samples under the water saturation conditions. The relationship between εr and εd had been obtained. The decreasing of uniaxial compressive strength of dry and saturated samples with increasing of the number of freeze-thaw cycles was analyzed. The linear relationship between freeze-thaw times and sample deterioration was determined. Finally, the influence mechanisms of water saturation condition, lithology and fracture condition on freeze-thaw cyclic deformation of rock mass were discussed.
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Key words:
- fractured rock mass /
- freezing-thaw cycle /
- freeze expanding value /
- residual deformation
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图 5 饱水裂隙试样冻融循环次数-εd关系曲线
Figure 5. Relationship of freezing-thawing cycle with εd of the saturated fracture samples
图 6 饱水裂隙试样冻融循环次数-εr关系曲线
Figure 6. Relationship of freezing-thawing cycle with εr of the saturated fracture samples
图 7 干裂隙试样冻融循环次数-εr关系曲线(正值为千枚岩、负值为砂岩)
Figure 7. Relationship of freezing-thawing cycle with εr of dry frcture samples
图 8 饱水裂隙试样εd-εr关系曲线
Figure 8. Relationship of εd with εr of the saturated fracture samples
图 9 干裂隙试样εr-饱水裂隙试样εr关系曲线
Figure 9. εr relationship of situated fracture samples with dry fracture samples
图 10 干燥裂隙试样冻融变形影响因素
黑底标记为砂岩, 白底标记为千枚岩, 下图同
Figure 10. Effect factors on freezing-thawing deformation of dry fracture samples
图 11 饱水裂隙试样冻融变形影响因素
Figure 11. Effect factors on freezing-thawing deformation of the saturated fracture samples
图 12 水对裂隙试样冻融变形影响
Figure 12. Effect of water on freezing-thawing deformation of fracture samples
图 13 冻融条件下干燥岩体矿物差异性变形损伤
a.含不同矿物(矿物冻融变形大小不同，深色矿物变形大，浅色矿物变形小)岩体; b.“冻缩”过程(虚线)，矿物非协调变形产生拉应力，产生损伤(红色短线); c.“热胀”过程(虚线)，矿物非协调变形产生挤压应力，产生近一步损伤(红色短线)
Figure 13. Deformation damage of mineral difference of dry rock in freezing-thawing condition
图 14 饱水岩体孔隙水冻胀损伤
a.含孔隙岩体; b.孔隙饱水，冻结过程孔隙水结成冰，产生冰胀力，造成残余拉张变形和损伤(红色短线)
Figure 14. Freezing-thawing damage of pore water of the staturated rocks
图 15 饱水裂隙岩体冻胀冰劈损伤
a.裂隙饱水; b.冻结冰劈过程，裂隙水冻结为冰，冰劈力使裂隙尖端扩展; c.试验结束后，尖端处形成闭合损伤裂隙
Figure 15. Freezing-thawing damage of the saturated rock mass
图 16 单轴抗压强度与冻融次数关系曲线
Figure 16. Relation curve between uniaxial compressive strength and freezing-thawing cycle
表 1 岩体物理参数
Table 1. Physical parameters of rock mass
试样类别 密度ρB/(g·cm-3) 孔隙率n/% 吸水率ωa/% 单轴抗压强度/MPa 超声波波速/(m·s-1) 干燥 饱和 干燥 饱和 千枚岩 2.77 0.50 0.18 35.2 18.8 5 608 5 902 砂岩 2.70 1.22 0.45 88.2 76.9 4 581 5 131 
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表 2 试验方案
Table 2. Test program
类别 裂隙试样 裂隙 干燥 饱水 长度/cm 宽度/mm 数量/条 千枚岩 S1-1 S1-2 1/4h 3 1 S1-3 S1-4 1/2h 3 1 S1-5 S1-6 3/4h 3 1 S1-7 S1-8 1/2h 3 2 S1-9 S1-10 1/2h 6 1 砂岩 S2-1 S2-2 1/4h 3 1 S2-3 S2-4 1/2h 3 1 S2-5 S2-6 3/4h 3 1 S2-7 S2-8 1/2h 3 2 S2-9 S2-10 1/2h 6 1 注：h为试样高度
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表 3 饱水裂隙试样εr
Table 3. Results of εr of situated sample
试样 冻融循环次数/次 残余微应变εr/με S-2(1/4 h) S-4(1/2 h) S-6(3/4 h) S-8(双裂隙) S-10(6 mm) S1/千枚岩 1 20 28 40 80 46 10 22 37 56 106 69 20 31 49 81 139 92 30 43 61 98 175 118 40 59 82 119 202 141 50 71 102 145 228 169 S2/砂岩 1 30 62 66 118 98 10 37 71 94 149 129 20 60 90 125 196 156 30 72 110 167 235 200 40 91 123 210 276 244 50 105 139 253 308 303
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表 4 干燥裂隙试样εr
Table 4. Results of εr of situated sample
试样 冻融循环次数/次 残余微应变εr/με S-1(1/ 4h) S-3(1/2 h) S-5(3/4 h) S-7(双裂隙) S-9(6 mm) S1/千枚岩 1 12 14 17 37 22 10 16 20 26 58 38 20 21 29 34 80 55 30 29 38 41 98 75 40 39 61 64 125 98 50 51 60 68 161 125 S2/砂岩 1 -96 -99 -102 -120 -119 10 -118 -125 -130 -152 -138 20 -146 -160 -162 -187 -167 30 -169 -182 -191 -209 -198 40 -188 -196 -202 -211 -206 50 -191 -200 -205 -213 -209
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