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VERTICAL ZONING CRITERIA AND ENGINEERING GEOLOGICAL CHARACTERISTICS OF SUPER-THICK LAYER GRANITE WEATHERING CRUST IN WUZHOU CITY
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摘要: 本文选择华南地区巨厚层花岗岩风化壳分布区的梧州市为研究区，旨在建立系统的、科学的、可操作性强的花岗岩风化壳垂直分带划分标准。在野外区域调查、钻探、原位试验、室内试验、综合研究的基础之上，建立了定性与定量复合判定的指标体系，对梧州市花岗岩风化壳进行了垂直分带以及工程地质特征研究。研究结果表明：(1)粒度分析法可以作为花岗岩风化壳垂直分带划分的方法之一，划分结果与原位试验划分结果具有很好的一致性；(2)残积土带、全风化带、强风化带中含量占比最大的土体分别是黏粒土、粉粒土、砂粒土。随着钻孔深度的增加，粒径相对较大的砾粒和砂粒含量占比逐渐增大，粒径相对较小的粉粒和黏粒含量占比逐渐减小。粒径0.05 mm为残积土带、全风化带、强风化带曲线交叉的分界处，该处土体含量百分比近似相等，揭示粒径0.05 mm值是花岗岩风化壳垂直分带划分的重要指标之一；(3)随着钻进深度的增加，圆锥动力触探试验击数与标准贯入试验击数同时增加，修正后的标准贯入击数N和圆锥动力触探击数N63.5呈多项式相关性。本文建立了花岗岩风化壳垂直分带划分标准，给出了花岗岩风化壳土体地基承载力建议值，对花岗岩分布区的重大工程建设与工程地质特征参数的选取具有一定的指导与参照意义。Abstract: Wuzhou City is the distribution area of the granite weathering crust with huge thickness in South China. It is selected as the study area. The study aims to establish a systematic,scientific,and operable standard for the vertical division of granite weathering crust. On the basis of field investigation,drilling,in-situ test,laboratory test,and comprehensive research,an index system of qualitative and quantitative composite judgment is established. The vertical zoning and engineering geological characteristics of granite weathering crust in Wuzhou City are studied. The studies show that: (1) Granularity analysis can be used as one of the methods of vertical zoning of granite weathering crust. The division results are in good agreement with the results of the in-situ test division. (2) Clay,silt and sand soil account for the largest proportion in residual soil zone,completely weathered zone and strongly weathered zone,respectively. The size of soil particles increases with increasing depth. The proportion of gravel and sand particles with relatively large particle sizes gradually increases. The proportion of powder and clay particles with relatively small particle sizes gradually decreases. Particle size 0.05mm is the boundary of curve intersection of residual soil,fully weathering zone and strongly weathering zone. The percentage of soil content at this place is approximately equal,revealing that the value of 0.05mm particle size is one of the important indicators for the vertical division of granite weathering crust. (3) With the increase of the drilling depth,the number of cone dynamic penetration test hits and the number of standard penetration tests increase simultaneously. The corrected standard penetration number N and cone dynamic penetration penetration number N63.5 show a polynomial correlation. In this paper,the standard of vertical zoning of granite weathering crust was established,and the recommended value of the bearing capacity of the granite weathering crust soil is given,which had certain guiding and reference significance for major project construction and selection of engineering geological characteristic parameters in granite distribution area.
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图 2 花岗岩风化壳垂直分带标准体系
Figure 2. Standard system of vertical zoning of granite weathering crust
图 3 部分钻孔粒度分布图(T1~Tn深度递增)
Figure 3. Granularity distribution map of granite weathering crust(T1~Tn depth increasing)
图 4 花岗岩风化壳垂直分带粒度分布图
Figure 4. Vertical zoning granularity distribution of granite weathering crust
图 5 标贯击数N与动探击数N63.5相关性分析图
Figure 5. Correlation analysis chart between standard penetration hits N and dynamic penetration hits N63.5
表 1 典型钻孔粒度分析数据
Table 1. Typical drilling granularity analysis data
钻孔编号 样品编号 砾粒/%
(>2 mm)砂粒/%
(2~0.075 mm)粉粒/%
(0.075~0.005mm)黏粒/%
(<0.005mm)GCK01 T1 4.7 37.6 33.5 24.2 T2 5.7 37.8 32.1 24.4 T3 7.0 32.7 24.7 35.6 T4 8.5 46.6 25.3 19.6 T5 11.9 45.9 26.0 16.2 T6 12.8 55.2 26.9 15.1 GCK13 T1 1.6 14.8 60.8 22.8 T2 3.5 16.6 60.1 19.8 T3 5.7 25.5 52.8 16.0 T4 9.9 40.9 34.5 14.7 T5 12.8 43.2 30.7 13.3 T6 23.6 43.1 22.7 10.6 GCK15 T1 5.6 15.1 44.5 34.8 T2 7.1 22.4 37.9 32.6 T3 9.7 28.7 35.0 26.6 T4 14.7 35.4 26.1 23.8 T5 15.4 39.3 23.8 18.5 T6 17.6 44.0 21.8 16.6 T7 23.7 45.4 18.4 12.5 GCK19 T1 0.1 21.7 52.5 25.7 T2 0.7 22.7 51.4 25.2 T3 1.8 23.1 49.5 25.6 T4 1.1 24.8 48.6 25.5 T5 1.3 28.1 45.7 24.9 T6 3.1 31.0 47.5 18.4 T7 4.0 33.3 45.5 17.2 T8 4.4 35.2 43.9 16.5 T9 8.2 39.9 37.5 14.4 
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表 2 花岗岩风化壳分带粒度分析表
Table 2. The granularity analysis table of granite weathering crust
分类 砾粒 砂粒 粉粒 黏粒 粒度/mm 10~5 5~2 2~0.5 0.5~0.25 0.25~0.075 0.075~0.05 0.05~0.01 0.01~0.005 <0.005 残积层/% 1.80 3.05 9.31 4.28 7.68 6.00 23.63 15.44 28.83 全风化层/% 2.38 4.90 12.63 8.06 13.62 6.57 21.48 10.97 19.39 强风化层/% 3.52 6.27 18.49 9.16 14.40 6.92 17.79 8.50 14.65
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表 3 梧州市花岗岩风化壳垂直分带标准
Table 3. Vertical zoning criteria of granite weathering crust in Wuzhou city
一级指标 定性指标 定量指标 二级指标 野外特征 挖掘、钻进及岩芯特征 原位试验 土工试验 岩体强度试验 三级指标 颜色 结构特征 矿物特征 可挖掘特征 可钻进情况 锤击情况 岩芯完整程度 修正标贯或动探击数/击 粒度分析 内摩擦角/(°) 黏聚力/kPa 单轴抗压强度/MPa 残积土带 褐黄色、黄褐色，无光泽 呈土状，含大量石英颗粒，可取原状土样，具有可塑性 矿物已全部风化成土状，肉眼难见矿物颗粒 镐、锹挖容易 钻进容易 不回弹 土体柱状岩芯，较完整 标贯范围5.43~16.58，平均值12.64。 黏粒≥25%、粒径>0.05 mm含量≥60% ≤18 ≥45 — 全风化带 黄褐色、灰褐色，光泽暗 呈砂砾状，原岩结构破坏，难取原状土样，稍具塑性 长石风化成土状，黑云母、角闪石晶形已消失 镐、锹可挖 钻进较容易 不回弹，手捏易碎 取不出完整岩芯，呈松散砂砾状 标贯范围10.36~24.20，平均值18.40 黏粒15%~25%、粒径>0.05 mm含量45%~60% 18~25 30~45 — 强风化带 黄褐色、灰黑色，擦面有光泽 原岩结构基本破坏，风化不均匀，具有球状风化特征，岩芯呈土夹碎块状，不能取土样 长石、云母风化成次生矿物，局部残留未全风化长石晶体 镐、锹挖较难 上部钻进易，下部钻进难 锤击声哑，局部块状岩芯有较大回弹 难取出完整岩芯，较不完整，局部呈块状 标贯范围30.30~75.46，平均值50.20；动探范围8.04~30.51，平均值16.75 黏粒≤15%、粒径>0.05 mm含量≤45% ≥25 ≤30 天然抗压强度0.061~0.271 MPa，平均值0.191 MPa 中风化带 岩石稍暗，裂面呈黄褐色 裂隙发育，沿裂隙风化强烈，有蚀变特征，石英脉发育，可取岩体块状样 除部分黑云母见黄色浸染，其他矿物基本无变异，用指甲刮不易留下痕迹 — 岩芯钻具，可干钻 锤击声脆，有强回弹 岩芯较完整，呈块状-短柱状 — — — — 干燥抗压强度40.1~90.0 MPa，平均值68.8 MPa；饱和抗压强度36.7~79.1 MPa，平均值62.3 MPa 微风化带 颜色较新鲜 断面新鲜，沿裂隙有风化蚀变现象，可取柱状岩体样 与新鲜岩石差别不大，矿物未风化 — 岩芯钻具，不易干钻 声音清脆，锤击时震手 岩芯完整，呈长柱状 — — — — 干燥抗压强度69.4~141.0 MPa，平均值90.8MP；饱和抗压强度45.3~98.9 MPa，平均75.6 MPa 新鲜岩带 此次钻探未揭露，新鲜花岗岩带，完整，未风化
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表 4 标贯击数N和动探击数N63.5实测表
Table 4. The table of standard penetration hits N and dynamic penetration hits N63.5
钻孔编号 深度/m 动探N63.5/击 标贯N/击 GCK19 9.80 11.44 26.60 12.70 14.10 27.64 20.30 22.34 33.36 26.70 24.63 36.25 35.50 30.22 42.28 GCK8 12.45 10.86 18.48 20.30 11.00 23.81 23.70 21.23 38.53 25.00 25.65 41.14 GCK10 4.80 8.86 15.34 14.30 10.35 19.40 15.80 11.02 28.58 19.00 12.88 29.33 27.00 14.45 29.65 35.50 18.64 30.13 40.00 19.43 37.39 55.00 22.23 34.13
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表 5 标准贯入试验确定的地基承载力经验公式
Table 5. Empirical formula of foundation bearing capacities determined by standard penetration
序号 公式 适应范围 出处 1 fk=80+20.2·N(N=3~18) 黏性土、粉土 武汉市规划设计院 2 fk=152.6+17.48·N(N=18~22) 黏性土、粉土 武汉市规划设计院 3 fk=72+9.4·N1.2 黏土质砂、粉细砂 铁道部第三勘察设计院 4 fk=-212+222·N0.8 粉土、粉细砂 铁道部第三勘察设计院 5 fk=-803+850·N0.1 中、粗砂 铁道部第三勘察设计院 6 $f_{k}=\frac{N}{0.003\;08 \cdot N+0.015\;04}$ 粉土 纺织工业部设计院 7 fk=105+10·N 细、中砂 纺织工业部设计院 8 fk=387+5.3·N(N=8~37) 老堆积土 冶金部长沙勘察公司 9 fk=12·N(条形基础FS=3) 黏性土、粉土 Terzaghi 10 fk=15·N(独立基础FS=3) Terzaghi 11 fk=8.0·N 日本住宅工团 fk为地基承载力，N为修正后标贯击数
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表 6 花岗岩风化壳分带地基承载力建议值
Table 6. Bearing capacity suggested value of granite weathering crust
分带 残积土带 全风化带 强风化带 计算公式 fk=80+20.2·N fk=72+9.4·N1.2 fk=-803+850·N0.1 适应范围 花岗岩残坡积粉土、粉质黏土 花岗岩全风化粉细砂土、砂质黏土、黏土质砂 花岗岩强风化中、粗砂层 标贯N/击 5.43~16.58 10.36~23.40 22.90~50.46 承载力建议
/kPa197~422 227~502 392~507
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