Reliability evaluation of flexibly soft contact earth pressure cell testing based on centrifugal tests on tunnels
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摘要: 开展一系列离心模型试验，选取线性误差、平均幅值误差、响应速率作为指标，基于隧道模型对柔性软接触新型土压计ESP-Ⅱ和两种国际代表性传统土压传感器（PDA、EPL-D1）进行对比评价，验证新研发土压力计测量的可靠性。主要结论如下：①静力状态下，ESP-Ⅱ、PDA、EPL-D1线性误差分别为19.36%，12.7%，21.0%，平均幅值误差为5.79%，48.2%，22.6%，证明ESP-Ⅱ土压力计相比国际两种土压计具有较好静力测试性能。②动力荷载下，ESP-Ⅱ、PDA、EPL-D1土压力计的平均响应速率分别为67.1，51.5，65.8 Hz，ESP-Ⅱ的响应速率略高于其他两种土压力计，具有良好的响应频率；序列地震动荷载下ESP-Ⅱ、PDA测得土压力与EPL-D1不同，呈现一致增量规律，而数值存在一定差异，反映土体具有较强结构性。③卸载过程中，3种土压力计测得数据均呈现不同程度的非线性变化特征，PDA和EPL-D1土压力时程曲线产生了偏折、跳变现象，而ESP-Ⅱ土压力时程曲线保持了较好数据连续性，一定程度说明软接触式设计能实现土压力计与土体的良好接触。Abstract: A series of centrifugal model tests are conducted by selecting the linear error, average amplitude error and response rate as the indice. Based on the tunnel model, a new flexibly soft contact earth pressure cell ESP-Ⅱ and two internationally representative traditional earth pressure sensors (PDA and EPL-D1) are compared and evaluated to verify the reliability of the newly developed earth pressure cell measurement. The main conclusions are as follows: (1) Under the static state, the linear errors of ESP-Ⅱ, PDA and EPL-D1 are 19.36%, 12.7% and 21.0%, respectively, and the average amplitude errors are 5.79%, 48.2% and 22.6%, indicating that the ESP-Ⅱ earth pressure cell has better static testing performance compared to the two international earth pressure cells. (2) Under the dynamic loads, the average response rates of ESP-Ⅱ, PDA and EPL-D1 earth pressure cells are 67.1, 51.5, and 65.8 Hz, respectively. The response rate of ESP-Ⅱ is slightly higher than that of the other two types of earth pressure cells, indicating a good response frequency. The earth pressures measured by ESP-Ⅱ and PDA under sequential seismic loads are different from those of EPL-D1, showing a consistent incremental pattern. However, there are certain differences in the numerical values, indicating that the soils have strong structural characteristics. (3) During the unloading process, the data measured by the three types of earth pressure cell show varying degrees of nonlinear changes. The time-history curves of earth pressures of PDA and EPL-D1 exhibit bending and jumping phenomena, while those of ESP-Ⅱ maintain good data continuity, indicating to some extent that the soft contact design can achieve good contact between the earth pressure cells and the soils.
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Keywords:
- tunnel /
- centrifugal model test /
- soft contact type /
- earth pressure cell /
- test reliability
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图 1 DCIEM-40-300型离心机振动台系统
Figure 1. Shaking table test system of DCIEM-40-300 centrifuge
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图 3 离心模型试验设计方案及实物图
Figure 3. Design scheme and physical image of centrifugal model tests
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图 6 连续振动荷载下土压力测量结果
Figure 6. Time histories of earth pressure under continuous vibration loads
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图 7 卸载过程3种土压力计测量结果
Figure 7. Measured results of three types of earth pressure cells during unloading process
表 1 原型/模型隧道参数
Table 1 Parameters of prototype/model tunnel
材料参数 原型材料 模型材料 弹性模量/GPa 35.5 71 隧道外径/mm 10000 200 隧道内径/mm 9000 190 衬砌厚度/mm 500 5 隧道长度/mm 20000 400 
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表 2 3种土压力计静力测量值及计算值
Table 2 Static measurements and calculated values of three types of soil pressure cells
离心加速度/g 土层深度/m 测量值/kPa 计算值/kPa ESP-Ⅱ PDA EPL-D1 5 1.25 9.26 — 37.83 18.13 1.75 4.33 5.82 9.34 11.15 2.25 — 53.01 61.40 34.43 10 2.5 15.66 — 59.52 36.27 3.5 14.10 18.21 25.33 22.30 4.5 — 76.09 83.67 52.57 15 3.75 21.24 — 76.17 54.40 5.25 22.98 33.64 45.13 33.44 6.75 — 94.24 106.14 70.70 20 5 26.14 — 90.65 72.53 7 30.98 51.34 67.03 44.59 9 — 111.45 126.32 88.83 35 8.75 38.52 — 130.59 126.94 12.25 55.01 114.05 142.16 78.04 15.75 — 152.51 178.98 143.24 50 12.5 51.36 — 174.97 181.34 17.5 78.37 174.82 216.41 111.48 22.5 — 191.26 227.81 197.64
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