Design And In-situ Tests Of Ground Treatment For A Large Thermal Power Plant

The Zouxian Power Plant is a national demonstration power plant in China, which is located at Tangcun town, Zoucheng City of Shandong Province. Four 300MW coal-fired units are performed called phase I and phase II, natural foundations are employed. As for phase III, two 600MW coal-fired units are conducted, natural foundations as well as plain concrete cushion were used. After operation, these three phases were running with well conditions.For phase IV, two large coal fired units of 1000MW are adopted, in this case the load of upper part is increased obviously. The investigation report for phase IV shows that the embedded depth of layer (1)—3—2 has the tendency to gradually lowering its top depth from the east (extension side) to the west, and at the main building area of phase IV, the embedded depth of layer (1)—3—2 is about 10m. It is known that the proposed embedded depth of foundation at the main building is 6m, with this depth the subsoil from 6m to 10m should be reinforced, or pile foundation are recommended to be performed.In conformity to our design practices of 600MW unit construction, gravelly course is greatly recommended for ground treatment of phase IV, with this cushion high bearing capacity and less settlement are obtained, and at the mean time,by this treatment, the characteristics of subsoil can be improved fundamentally, and the construction period can be controlled easily, and therefore the project can be completed earlier, with the result that remission the tension in supply of east China power network.If pile foundation is recommended to be into use, among all kinds of piles, only two piles called bored cast-in-place pile and tube pile used in this project, after comparison the gravelly course is recommended the optimum way for ground treatment.In order to prove the feasibility of the ground treatment for gravelly course, at the beginning two groups of mixure ratio based on engineering practice should be chosen, and the mixed samples should be sent to laboratory to obtain the relativedensity. Then, execute roller compaction test in-situ under different lift thickness marked with A and B for different area. During compaction density, moisture content as well as grain size analysis should be measured, and after compaction, static plate loading test, cyclic loading test, wave velocity mwasurment, subgrade hardness test, foundation slide test as well as dynamic sounding test have been performed. All the testing results indicate that Zone B with the thickness of 400mm is much better than that of Zone A with the thickness of 600mm.The ground treatment scheme used in this project has two points to be broken through the current building technical specification for ground treatment. Firstly, the eigenvalue of gravelly course adopted in this project (700kPa) is higher than that of the given value of 200-3 OOkPa, this value has been improved in other 600MW units project. Secondly, the thickness of 4m for gravelly course is larger than that of the thickness specified in the above current specification, in the specification the thickness of roller course is required not exceed 3m. The detection of construction poves that in practice, the exceed of thickness for gravelly course is feasible providing that in construction the thickness of compaction course and the requirements of compaction are strictly performed in accordance with the concerned construction specifications.