土体干湿过程引发的岩土工程问题已逐渐受到重视。通常采用张力计量测80 kPa以内的土体吸力,并将其应用于边坡失稳等岩土工程问题的分析中。然而,传统张力计由于内部腔体体积过大且结构复杂,造成张力计难以饱和,吸力量测时反应时间长,并易发生汽化,严重影响其可靠性和灵敏性。为弥补传统张力计的设计缺陷,提出了一种装配式新型张力计。该张力计内腔结构简单且体积小。饱和前先拆分张力计再分别饱和其主要部件,最后重新装配。此设计简化了饱和程序并提高了效率。通过对比传统张力计和新型张力计的性能,证实了新型张力计具有更强的汽化持久性,其吸力量测的灵敏性和可靠性得到了显著的提高。标定试验表明,相比于传统张力计,新型张力计的灵敏性提高了90%。测量-80 kPa的孔隙水压力时,新型张力计的平衡时间为1.5 min,仅占传统张力计反应时间的10%。相同的测量条件下,传统张力计的测量误差为30%,而新型张力计的测量误差仅为0.7%。
Ever more attention has been paid to geotechnical problems induced by wetting and drying of soils recently. Suction up to 80 kPa, measured by tensometers, has been used for analyzing geotechnical problems such as slope instability during wetting and drying. However, existing tensometer generally has a long response time and is easy to cavitate since it has a large volume of water reservoir and complicated internal structure. These drawbacks affect the sensitivity and reliability of a conventional tensometer seriously. In order to overcome these shortcomings, a newly developed fabricated tensometer is introduced. This type of new tensometer with fabricated structure has a simple internal structure and a small volume of water reservoir. At the same time, a drainage hole is introduced to prevent large excess pore water pressure during the process of reassembling. More importantly, its saturation procedure is simple and efficient since the high air-entry ceramic disc and pore pressure transducer of this new tensometer can be disassembled for saturation separately and effectively. After the saturation of the high air-entry ceramic disc and pore pressure transducer, these key components are reassembled together as a tensometer ready for use. As compared with a conventional tensometer, the sensitivity and reliability of this new tensometer are justified. The results of calibration test show that the sensitivity of the new tensometer increases by 90% by comparing with the conventional tensometer. In the case of measuring the pore water pressure of -80 kPa, the equilibrium time required for this new tensometer is only 1.5 minite, about 10% of that for the conventional tensiometer. Moreover, the reliability of the new tensometer is better than that of the conventional tensometer. The measurement error of the conventional tensiometer is about 30%, when measuring the pore water pressure of -80 kPa. Subjected to the same conditions, the new tensometer shows a measurement error of only 0.7%.