Soil Plug Effect Prediction and Pile Driveability Analysis for Large-Diameter Steel Piles in Ocean Engineering

Long steel piles with large diameters have been more widely used in the field of ocean engineering. Owing to the pile with a large diameter, soil plug development during pile driving has great influences on pile driveability and bearing capacity. The response of soil plug developed inside the open-ended pipe pile during the dynamic condition of pile-driving is different from the response under the static condition of loading during service. This paper addresses the former aspect. A numerical procedure for soil plug effect prediction and pile driveabihty analysis is proposed and described. By taking into consideration of the pile dimension effect on side and tip resistance, this approach introduces a dimensional coefficient to the conventional static eqnihbrium equations for the plug differential unit and proposes an improved static equity method for the plug effect prediction. At the same time, this approach introduces a simplified model by use of one-dimensional stress wave equation to simulate the interaction between soil plug and pile inner wall. The proposed approach has been applied in practical engineering analyses. Results show that the calculated plug effect and pile driveabihty based on the proposed approach agree well with the observed data.

Pit Bearing Capacity Effect on Status of Soil Plug During Pile Driving in Ocean Engineering

Foundation piles of the offshore oil platforms in the Bohai Bay are usually longer than 100 m with a diameter larger than 2 m. Driving such long and large-sized piles into the ground is a difficult task. It needs a comprehensive consider ation of the pile dimensions, soil properties and the hammer energy. Thoughtful drivability analysis has to be performed in the design stage. It has been shown that judging whether the soil column inside the pile is fully plugged, which makes the pile behave as close-ended, strongly influences the accuracy of drivability analysis. Engineering practice repeatedly indicates that the current methods widely used for soil plug judgment often give incorrect results, leading the designers to make a wrong decision. It has been found that this problem is caused by the ignorance of the bearing capacity provided by the soil surrounding the pile. Based on the Terzaghi＇s bearing capacity calculation method for deep foundation, a new approach for judging soil plug status is put forward, in which the surcharge effect has been considered and the dynamic effect coefficient is included. This approach has been applied to some practical engineering projects successfully, which may give more reasonable results than the currently used method does.

Objective Rating of the Launch Behavior of Conventional,Hybrid and Electric Vehicles

The calibration of conventional,hybrid and electric drivetrains is an important process during the development phase of any vehicle.Therefore,to optimize the comfort and dynamic behavior(known as driveability),many test drives are performed by experienced drivers during different driving maneuvers,e.g.,launch,re-launch or gear shift.However,the process can be kept more consistent and independent of human-based deviations by using objective ratings.This study first introduces an objective rating system developed for the launch behavior of conventional vehicles with automatic transmission,dual-clutch transmission,and alternative drivetrains.Then,the launch behavior,namely comfort and dynamic quality,is compared between two conventional vehicles,a plug-in hybrid electric vehicle and a battery electric vehicle.Results show the benefits of pure electric drivetrains due to the lack of launch and shifting elements,as well as the usage of a highly dynamic electric motor.While the plug-in hybrid achieves a 10%higher overall rating compared to the baseline conventional vehicle,the pure electric vehicle even achieves a 21%higher overall rating.The results also highlight the optimization potential of battery electric vehicles regarding their comfort and dynamic characteristics.The transitions and the gradient of the acceleration build-up have a major influence on the launch quality.