论文部分内容阅读
小应变下的土体模量的变化对基坑周围既有建筑物的变形和路基沉降分析具有重要意义。土体模量会随土体的应变呈非线性变化,特别是应变范围为10~(-5)~10~(-3),土体模量随应变的增加显著降低。由于土体应变的变化范围广,传统的单一测量仪器无法连续量测土体从微小应变到小应变的模量变化情况。通常测量土体小应变模量的方法有弯曲元和局部位移计方法。弯曲元方法能有效测量土体微小应变的模量,但不能得到土体模量在小应变情况下变化规律,因为弯曲元方法无法得到和控制土体的应变。设计了基于布拉格光纤光栅传感技术的局部位移计。通过设计和标定试验,成功将布拉格光纤光栅局部位移计应用于改装的三轴试验仪器中。为进一步的对比分析,在改进的三轴试验装置中安装了弯曲元试验系统。基于改装的三轴试验仪器,进行了不同围压下的固结不排水试验,得到了土体从微小应变到小应变下模量的变化曲线。试验结果验证了光纤光栅局部位移计能有效的测量土体在小应变情况下的模量非线性变化特征。
The change of soil modulus under small strain is of great significance to the deformation of existing buildings around the foundation pit and the settlement analysis of roadbed. The soil modulus will change nonlinearly with the soil strain, especially the strain range is 10 ~ (-5) ~ 10 ~ (-3). The soil modulus decreases with the increase of strain. Due to the wide range of soil strain changes, the traditional single measuring instrument can not continuously measure the change of soil from small strain to small strain. The commonly used method to measure the small strain modulus of soil is bending element and local displacement meter. The bending element method can effectively measure the modulus of soil microstrain, but can not get the variation law of soil modulus under the condition of small strain, because the bending element method can not get and control the soil strain. A local displacement meter based on Bragg grating sensing technology was designed. Through the design and calibration test, the successful application of the Bragg fiber grating partial displacement meter to the modified three-axis test instrument. For further comparative analysis, a bender element test system was installed in an improved triaxial test rig. Based on the modified triaxial test equipment, the consolidated undrained test under different confining pressure was carried out, and the curve of soil modulus from small strain to small strain was obtained. The experimental results verify that the FBG local displacement meter can effectively measure the nonlinear change of modulus under the condition of small strain.