Design And Research Of The Pile Foundation Of Main Building Of Jiaxing Power Plant Third Phrase

The2nd stage of Jiaxing Coal-fired Power Plant builds4×600MW power-generating units. Pile type for the main power building is ΦD609x12mm steel pipe pile, about63m long. The plant is put into service on October18th,2005. Up to now, on the basis of the settlement observation result, the maximum settlement of the main power building foundation has already been close to the limit value mentioned in the specification. The3rd stage of Jiaxing Coal-fired Power Plant is scheduled to construct2×1,000MW ultra super-critical power generation units. Compared with the data from the2nd stage, the main power building bears a greater upper load and its requirements on foundation settlement are stricter. There are so many essential issues that must be handled, such as whether it can still adopt piling model used to the previous stage; whether it is able to use the same pile bearing stratum; how to choose more economic pile type and more reliable pile bearing stratum on the basis of the prior construction experience and how to guarantee the safety and reliability of the construction and shorten the construction period at the same time.This article takes into consideration more complicated geological conditions of the3rd stage of Jiaxing Coal-fired Power Plant. Firstly, by means of analyzing the settlement observation data of the main power building and relevant sites on the in-service2nd stage project, and checking ground settlement rate of Jiaxing City, a comparison between the measured value and the calculating value of main power building settlement is conducted, which provides relative settlement and settlement coefficient of the2nd stage main power building for pile foundation calculation of the3rd stage project later. Secondly, the comparison is conducted on the three aspects of all pile types, which are respectively to the ratio of single pile bearing capacity basing on soil’s side resistance and tip resistance and pile reinforcement strength, the bearing capacity out of every hundred RMB investment, and the settlement of main power building pile with different pile bearing stratum. Through multi-aspect and multi-angle analysis of technology, economics and construction, more economic rationality pile types and pile bearing stratum are proposed. Thirdly, in order to meet the requirements on the pile depth into the bearing stratum and the thickness of pile bearing stratum, when thickness of some pile bearing stratum is thin, the influence of different pile tip depth into the bearing stratum on single pile bearing capacity and settlement is analyzed to optimize pile depth into the bearing capacity. Finally, an advanced piling design scheme of the main power building on the3rd stage project is put forward. By the trial driving project, some design and construction parameters are presented:(1) standard value of the single pile vertical compressive bearing capacity limit for chosing pile types;(2) pile deformation and single pile horizontal bearing capacity under horizontal loads without top constraint;(3) pile-driving equipments, hammer type and hammer-stopping standard during construction;(4) construction procedures and technical parameters of super-long drilled cast-in-place pile;(5) variable value of piling design parameters corresponding to the geological conditions changing, which enlarges the possibility to choose relatively-cheap pile type under better technical and economic conditions. All of these contribute to achieve the objective of saving project investment, controlling project process and advancing project quality.Currently, the3rd stage of Jiaxing Coal-fired Power Plant has been put into service in October,2011. According to the observation settlement data of the main power building foundation, the maximum settlement of the main power building foundation is about40mm until April,2012, which is far less than the settlement value of the2nd stage in the same period. That proves the reasonability and reliability of the foundation treatment scheme for the3rd stage of Jiaxing Coal-fired Power Plant evidently.