Analysis of Vertical Earth Pressure Acting on Box Culverts through Centrifuge Model Test

Due to the lack of surface space, most structures are heading underground. The box culvert is underground infrastructure and serves to protect the buried structure from the underground environments, but it has a different characteristic from other structures in that the inner space is empty. Therefore, in this study, the vertical earth pressure which is the most significant effective stress acting on a box culvert was measured by conducting a geotechnical centrifuge model test. A box culvert was installed following the embankment installation method, and the vertical earth pressure acting on it was measured considering the cover depth, gravitational acceleration, and loading and unloading conditions. The soil pressure measured was greater than the existing theoretical value under high cover depth and the unloading condition, which is considered as the variability of many soils or the residual stress acting under the loading condition. Finally, a goodness-of-fit test was conducted as a part of variability analysis. The measured earth pressure was found to be considerably larger than the existing theoretical value, and the variability was large as well. This means the existing theoretical equation is under-designed, which should be reflected in future designs.

Dynamic behavior of pile-supported wharves by slope failure during earthquake via centrifuge tests

The effects of earthquakes on pile-supported wharves include damage to piles by inertial forces acting on the superstructure, and damage caused by horizontal displacement of retaining walls. Piles can also be damaged through kinematic forces generated by slope failure. Such forces are significant but it is difficult to clearly explain pile damage during slope failure since the inertial force of superstructure and the kinematic force by slope failure can occur simultaneously during an earthquake. In this study, dynamic centrifuge model tests were performed to evaluate the effect of the kinematic force of the ground due to slope failure during earthquake on the behavior of a pile-supported wharf structure. Experimental results indicate that the slope failure in the inclined-ground model caused the deck plate acceleration and pile moment to be up to 24% and 31% respectively greater than those in the horizontal-ground model due to the kinematic force of the ground.

Prefailure Deformation of Nailed Deep Excavations under Surcharge by Centrifuge Model Test

To study prefailure deformations in nailed deep vertical excavations under various surcharges, four centrifuge tests were used to explain the lateral deformation of facing, the fracture mechanism of cement facing, and the settlement profile of the ground surface. The soil used in this research was Firoozkooh sand No. 161. Both surcharge applying and excavation were performed at 40 g acceleration. The depth of the excavation was 30 cm, the length of the nail varied from H/3 to 2H/3 (H: excavation depth), and the nails were installed horizontally. The nails were made of brass pipes and then sand coated. The results showed that the effect of surcharge on the lateral deformation of the facing as well as the fracture mechanism of facing is obvious. Also, it was seen that the ground settlement profile is two-line or three-line at the moment of facing fracture and is affected by surcharge.

Investigation on the Settlement of High Rockfill Embankment Using Centrifuge Tests

To study the deformation behavior of the high rockfill (HRF) embankment during construction and operation, based on more than a 50-m high rockfill embankment of the second-class road reconstruction project from Xunyang to Ankang of the national road 316 in Shaanxi, China, the centrifuge model test was performed to study the deformation laws of HRF embankment. The test results showed the following: (i) the HRF embankment was stable during construction and operation; (ii) during construction, the settlement occurred at the embankment top, and uplift occurred at the slope foot. Moreover, the deformation at the top was greater than that at the slope foot, and the deformations at both the top and the slope toe reached the maximum value at the end of construction; (iii) during operation, the settlement at the embankment top continued, and it changed rapidly at the start of operation. And then, the rate of the settlement slowed down and reached a steady state finally. The deformation of the slope foot was very small. This study can provide basis and reference for the design and construction of a similar project in mountain areas.