A Study On Practical Applications Of Composite Ground Theory Of Granular Material Pile In Power Engineering

Concept of composite ground was initiated in 1962 from application and study on granular material piles such as sand pile. With development of engineering practice and theoretic study on ground treatment of various kinds of new forms, the content included in the concept of composite ground has been vigorously enlarged and developed from the composite ground made of non-binding granular material pile to those made of soft materials such as various kinds of concrete pile with certain adhesive strength and those of high strength rigid pile. The conceptual development of composite ground fits for massive engineering practice of ground treatment. Power construction projects, especially technical features of power generation projects themselves, set forth higher requirements for subgrade of building structures. The unit installation capacity of thermal power plant has been increased from the 200MW in 1980s to the present 600MW. So far the project adopting generator unit of 800MW installation capacity of 800MW (Shuizhong Power Plant) has been completed and put into operation, and the project adopting generator unit of 1000MW installation capacity has been already in progress of construction (Shanghai Waigaoqiao Power Plant, and Zhejiang Huaneng Yuhuan Power Plant). Moreover, since China has a vast territory, various kinds of disastrous geological issues have to be frequently encountered and special rock and soil are widely distributed, which, as unfavorable conditions, cannot be avoided during the construction of power projects. Due to importance of power projects, when coming across with weak subgrade, main building structures for many projects may adopt pile foundation ofdifferent types (rebar concrete square pile, driven concrete cast-in-place pile of large diameter, pre-stressed concrete pipe pile of high strength, steel pipe pile, and H-steel pile), and resultantly, the cost of works has been increased, which produces very practical significance for study and application of more economical ground treatment methods. Many projects have launched beneficial practice in this field, and achieved good result. The composite ground of granular material pile in power projects has been widely used in construction of power projects for twenty years or so, during which a lot of engineering experience have been accumulated. However, there are many issues to be studied for engineering application because of imperfect theoretic system of composite ground of granular material pile, which remains under development. Therefore, it is necessary to study and summarize the application of composite ground of granular material pile in construction of power projects, and the result will provide useful information and guidance to construction of future projects. This thesis carries out systematic analysis on theoretic issues of composite ground of granular material pile in the aspects of reinforcement mechanism, bearing capacity, settlement calculation, and earthquake liquefaction elimination, etc. It also makes detail study on existing calculating and analyzing methods. On such a basis, in consideration of technical features of power construction projects and experience in application of composite ground of granular material pile, it forwards the guiding principle on designing composite ground of granular material pile for power construction projects; and combining theoretic calculation of practical cases and on-the-spot test and study, it achieves ideal consistency between result of calculation and analysis and test on site, while the project application result also achieves good economical benefits.Main achievements and conclusions of this thesis are as follow: Firstly, this thesis reviews the course of theoretical development for the composite ground of granular material pile, and on such a basis, it carries out systematic analysis and discussion on load transfer features destroymodes of the composite ground of granular material pile, and expounds the main possible destroy mode of the composite ground of granular material pile.The load b...