دانلود رایگان ترجمه مقاله عدم قبول پیش رس شمعهای قطر بزرگ در یک پلت فرم دریایی – الزویر 2013

مقاله انگلیسی رایگان

ترجمه فارسی رایگان 

بخشی از مقاله انگلیسی:

Abstract

Open-ended pipe piles are commonly driven into the seabed to support offshore platforms. This paper presents a case of practical offshore driven pile installation experiences associating with premature refusal. Pile drivability and capacity are analyzed using sufficient driving records. Dynamic loading tests were performed three months after the driving in order to determine the pile capacity after refusal. The test results are detailed in this paper compared with back analysis of measured pile driving records. Empirical equations are provided to predict soil resistance during driving and after setup according to the driving records and dynamic loading tests. Analyzing this practical engineering case is hoped to lead to a better understanding of pile driving, especially when premature refusal occurs. The sufficient details of the engineering data in this paper are also expected to enrich the engineering experience and literature of offshore piles in offshore engineering.

1. Introduction

Steel jacket structures are still the most common form of fixed offshore platforms, which are fixed to the seabed by piles inserted through sleeves attached to the jacket and the piles are eventually grouted to the sleeves after installation. One of the most common construction problems for driven piles is associated with the incorrect choice of design penetration, resulting in either insufficient bearing capacity or premature refusal [1]. Examples of premature refusal and associating collapse of pile tip were reported in the literature [2–4]. Removal ofthe soil plug inside the pile by drilling or jetting is normally required in this scenario in order to further drive the pile to reach the targeted depth, which will inevitably increase the cost significantly and delay the project completion [5]. Up to now, considerable amount of studies have been conducted from different perspectives to understand pile drivability and associated issues. Brunning and Ishak [6] tried to improve reliability of the pile driving predictions in carbonate soils and rock based on installation data in Timor Sea. Mohamad et al. [7] studied the effects of high-rebound of soil on pile drivability using static and dynamic tests. In addition, cone penetration tests (CPT) were highly recommended to make prediction of pile drivability in recent years [8,9]. All these available studies have shown that there are many factors affecting pile drivability, such as the hammer driving system characteristics, pile type, size and length and soil resistance behavior. According to  Stevens [10], premature refusal is likely due to significant end bearing in granular soils or soil setup, i.e. the time-dependent change in pile capacity. Although the state-of-the-art approaches have allowed significant advances in the analysis ofthe problem,the understanding of pile–soil interactions during pile installation is still quite limited. The majority of the current design approaches are still empirical based [11]. Highquality information, especially associating with practical engineering projects, on large-diameter, deep-penetration piles is difficult to find in the literature. This paper presents sufficient details of a real engineering project with premature refusal occurring, including pile driving records, retrospective analysis and dynamic testing 3 months after the refusal. These practical data and recorded information were analyzed toward a better understanding of the pile–soil behavior.