Influence of Cavity above Tunnel on Stratum Deformation and Failure in Urban Tunnelling

In order to study the influence of cavity above the tunnel on stratum deformation and failure in urban tunnelling, the model test method was adopted based on the parameters of the stratum and tunnel section size in Beijing subway. The stratum responses were obtained under the conditions without ground cavity and with ground cavity above the tunnel. The responses include the stratum stress distribution, stratum settlement law and stratum failure process. It was concluded that the existence of ground cavity above the tunnel worsened the stratum condition and accelerated the progress of stratum deformation and failure. Furthermore, the failure began from the cavity and the damage scope was bigger than that under the condition without cavity according to the test results. The research results can be referenced for the similar tunnel engineering.

The Deep-Basined Metate of the Southern California Coast

Deep-basined metates are frequently found in early sites on the southern California coast, but the faces of the accompanying manos usually are only moderately convex. Mano faces examined by the writer never have been sufficiently excurvate to make contact with the grinding surfaces of the deeply ground metates. This presents an interesting problem: how were the manos manipulated on the metates?An examination of specimens from Oak Grove sites 7, 21, and 79 (Rogers, 1929) and the Smithsonian Institution River Basin Surveys’ sites 4SBa477 and 4SBa485 in Santa Barbara County, California, reveals the following associations and characteristics. Slab, shallow-basined, and deep-basined metates are found in association. The first two types exhibit an unbroken grinding area, but specimens of the latter almost invariably have a slight shoulder running at least a part of the way around the basin, the transition between a slightly concave ground area and the deeply ground cavity.