Loading Behavior of Shallow Foundation in an Artificial Poorly Cemented Sandstone

• Main Authors: Chih-Wei Liao, 廖智偉
• Other Authors: Jyh-Jong Liao
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/19063269650758585551

碩士 === 國立交通大學 === 土木工程系 === 91 === This study aims to investigate the loading behavior of shallow foundation in poorly cemented sandstone. In this thesis, an artificial weak rock was developed as the foundation material. The mechanical behavior of the artificial rock is analogous to the natural sandstone. A set of laboratory loading equipments for foundation model was assembled. The loading capacity of the loading facility is up to 400 tons. The samples were prepared and loaded in a steel box with the dimension of 60 cm x 30 cm x 65 cm. To observe the fracturing of the specimen during test, a observed window was made on the upper and central part of one of the wall of the box using high strength glass. The deformation sensors made by FBG and TDR were adopted for measuring the deformation in the specimens during the test. Then, six sets of model loading tests were performed in the laboratory. Based on the observation of fracturing of the models from the window and the failure foundation models after the tests, the failure foundation models can be divided into four particular zones, i.e., the active stress zone, the passive stress zone, the shear-crack zone, and undisturbed zone. The fracturing was developed radially from the passive zone. The active zone located beneath the footing. It was induced by the stress concentration at the corner of the footing. The passive zone was formed by the lateral expansion of the active zone. The shear fractures increase with the increase of the loads. Then, a macro shear slip surface forms and extends to the surface. Since both the shear and tensile cracks were observed in the models, the loading behavior of model foundation of poorly cemented failure mode is little difference with those for hard rocks or soils. The measured deformation from FBG shows that the closer of the sensors with the footing is the larger of the deformation of the footing foundation. The fact reflects the FBG sensor is suitable for measuring the deformation in the test specimens. The calculated results from TDR sensor indicate the location of the change of the waveform is the same as the cracking location in the footing models. Hence, the TDR sensor can be used for monitoring the fracturing during loading test.