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摘要:
强夯夯沉量的准确预测对其设计施工至关重要。我国规范中地基土静荷载沉降计算多采用分层总和法，该方法简便实用，且工程经验丰富。强夯冲击荷载下的竖向动应力分布与静荷载下按弹性理论计算的土中附加应力分布类似。在此基础上，借鉴分层总和法思路，提出一种计算强夯夯沉量的拟静力实用计算方法。通过便携式落锤弯沉仪试验和贯入仪试验，对计算方法中涉及的动荷载特性参数及动回弹模量与压缩模量的关系进行了初步探讨，建议了平均夯锤接触动应力的计算方法。为验证所提夯沉量实用计算方法的有效性，将3个工程实例的实测夯沉量与计算夯沉量进行对比分析，结果表明：所提方法能较好地反映地基土体在不同能级下夯击的沉降特性，对于低、中、高3种不同能级的强夯工程，计算夯沉量与实测夯沉量的相对误差分别为2.28%、2.27%和9.89%。所提强夯夯沉量实用计算方法公式简单，使用方便，可为冲击荷载作用下地基土的沉降计算提供新思路。
Abstract:Accurately predicting the compaction settlement under the impact load of dynamic compaction has an important impact on the design and construction of dynamic compaction. The calculation of subgrade soil settlement under static load generally adopts the layered summation method in China. The layered summation method is simple and practical with rich engineering experience. According to the analysis of the dynamic stress in the soil-hammer contact, the additional stress distribution in the soil determined by the elastic theory under static load is comparable to the vertical dynamic stress distribution under the impact load of dynamic compaction. Based on the layered summation method, a practical calculation method for the compaction settlement of dynamic compaction is proposed. By using a portable drop hammer deflection test and a penetrometer test, a preliminary discussion was conducted on the dynamic load parameters involved in the calculation method, as well as the relationship between the dynamic rebound modulus and compression modulus. Meanwhile, a calculation method for the average contact dynamic stress of the hammer was provided. Lastly, a comparison between the measured and estimated settlement of three engineering examples was carried out in order to confirm the efficacy of the suggested practical calculation approach for compaction settlement. The results show that this method can effectively capture the settlement characteristics of subgrade soil under different energy levels of compaction. For dynamic compaction projects with low, medium, and high energy levels, the errors between calculated settlement and measured settlement are 2.28%, 2.27%, and 9.89%, respectively. This practical calculation method is simple and convenient to use, which provides a new approach for calculating the settlement of subgrade soil under impact loads.
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图 4 动回弹模量$ {E}_{\text{vd}} $与压缩模量$ {E}_{\text{s}} $的关系曲线
Figure 4. Relationship curves between dynamic rebound modulus $ {E}_{\text{vd}} $ and compression modulus $ {E}_{\text{s}} $
图 6 等效半正弦形式夯锤接触动应力时程关系曲线
Figure 6. Equivalent half-sine hammer contact dynamic stress-time relationship curves
图 7 西藏某机场强夯工程计算结果比较
Figure 7. Comparison of engineering calculation results for an airport dynamic compaction project in Tibet
图 8
6000 kN·m工况计算结果对比Figure 8. Comparison of calculation results under the
6000 kN·m operating condition
图 9
10000 kN·m工况计算结果对比Figure 9. Comparison of calculation results under the
10000 kN·m operating condition表 1 便携式落锤弯沉仪试验数据
Table 1. Test data of PFWD
实验
编号夯沉量$ {s}_{1} $/mm 夯沉量$ {s}_{2} $/mm 夯沉量$ {s}_{3} $/mm 平均夯沉量s/mm 动回弹模量Evd/MPa 1 1.027 1.006 0.996 1.010 22.2 2 0.892 0.866 0.861 0.873 25.7 3 1.010 0.989 1.006 1.002 22.4 4 1.002 1.003 0.975 0.993 22.6 5 1.019 0.990 0.964 0.991 22.7 6 0.941 0.911 0.893 0.915 24.5 
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表 2 贯入仪试验数据
Table 2. Test data of penetration
实验
编号贯入阻力
P1/N贯入阻力
P2/N贯入阻力
P3/N平均贯入
阻力P/N承载力
特征值fak/kPa压缩模量
Es/MPa1 33.1 29.8 32.0 31.63 289.1 5.74 2 29.2 25.9 28.1 27.73 256.6 5.19 3 25.3 25.8 31.2 27.43 253.9 5.17 4 28.6 25.4 25.4 26.47 245.7 5.02 5 33.1 31.8 34.8 33.20 301.9 5.83 6 30.8 32.1 30.0 30.97 283.7 5.65
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