Study On Design And Bearing Capacity Dection Of Large Pile Foundation Under Bridge

The pile foundation have already used in our country for large-scale bridge engineering adopted leading foundation forms. It belongs to concealed engineering scope. The pile foundation have many advantages, in possession of high bearing capacity, capable stability, little and homogeneous sedimentation capacity, facility for mechanician construction and intensive applicablity. In order to guarantee pile foundation's engineering quality, verify designed production. It requires carring through necessary detection in front of design and after construction. Therefore, it brings forward higher request to detection technique. In company with load-carrying properties, method of designing, detection technique, we probe into in-depth ceaseless investigation. Pile foundation's design theory and detection method for bearing capacity are incessantly renovated and advanced.At present, pile foundation design theory is much more apt to probability limit state design method, it gives out scientific measurement to dependability of pile foundation. Design forumla is unambiguous, transfer modus operandi relied on experience which adopted fixed-value security modulus. Simultaneously, with traditional fixed-value design method are complementary.Detective methods to pile foundation bearing capacity mostly include static loading test, stir measure test(low strain dynamic test, high strain dynamic test), self-balanced loading test, statnamic test, etc. Thereinto, self-balanced loading test and statnamic test are new technique developing newly arisen, possess many dominance, furthermore we have been taken definite efforts in practical engineering. Application for further gain is extremely wide. Conventional static loading test considers most credible method for pile foundation, but it is restricted for condations, such as lasting test work hour, large quantity, high testing expense. Furthermore it requests rigorous testing ground, bridge pile foundation's individual pile ultimate bearing capacity is more and more large, which bring out hardness augmentation, wherefore people usualy fench with doing static loading test. Stir measure test usually regards as pile foundation acceptable instrument, quality effect detection credibility, dynamic loading process differs discrepancy with actual loading, lower dependability, for the moment it can't substitute static loading test. Statnamic test have been accompanied with merits including static test and stir test, test result is consistent with static test. Yet the method bringing to bearing counterforce dissatisfy major diameter long pile, many factors influence it, for man-made, software, circustance, etc. Persons often oppugn its reliability, it has been used in abroad widely, but in our country still run short of systematic study and engineering practice. As for new technique self-balanced test takes definite efforts for application and research in our country, device simplicity, unoccupany floor, save testing expence, become a new detective method gradually. The paper mostly proceed several aspects under research:1. From probability theoretic angle, we analyse pile founation design, still maintain prodigious uncertainty, it might exerts highly limits potential with clustered piles, soil, superstructure and economy. We introduce probability limit state design method in theory, toward some calculated mode and parameter still lack definite and systemic finding, it has a long space with2. Handling linear elastic theory analyses load transferred mechanism under pile and soil. From four sapects, test principle, formula theory, test process and analysis of results introduce statnamic test detecting pile foundation bearing capacity, as a new technology and method, in our country need more develop aim at its research. So that we can apply it in engineering practice preferably in future. 3.The paper investigate self-balanced test's test principle, test system, test method,introduce confirmation of individual vertical bearing capacity with the method, induce the sorts of positionfor load case in point,offer theorical gist for practical engineering.4.Research bearer takes Jilin Lanqi Songhua Jiang large-scale bridge of national major project, detect its filling pile's bearing capacity with self-balanced test. We get across geological survey, from landform physiogomy, stratum lithology, geological structure, hydrological geology and regional earthquake environmental aspects, investigate geologic setting of the region to test piles. Contrast with Longhua Songhua Jiang large-scale bridge, offer detailed geology gist for uniform engineering conceptual design.5.As we analyze test data for Lanqi large-scale briedg project, according to the curve for connection of load and subsidence gotten from spot test detection. Then we go through with theoretical derivation and analysis to the sorts of trial curves, the results analyze large pile foundation load bearing characteristic in self-balanced test state. Detrude pile body axes force, side friction force, pile tip resistance force's calculative expression, arriving at individual pile bearing capacity, side friction force and tip resistance limit eigenvalue.6.Analyze the curves has gotten regularities of distribution of pile, there are closely related to each other for pile-soil relative displacement and exertion of pile friction, tip resistance of piles. Also, with construction technology of pile foundation. It is related just with stratum lithology and degree to efflorescence.7.In the end, the paper sum up and induce transferred method, load-subsidence curve which gotten from self-balanced test converts to pile top-displacement curve which equivalent to traditional static test. We proceed superposition load of airward and oversee form be measured in self-balanced test and corresponding displacement, then fitting, coming by these course, we convert to Q-S curve. Judging by the transformation curve we verdict individual pile ultimate bearing capacity, contrast the test results to converted test results,they are comparatively accord. The paper analyze the practical engineering, similar bridge pile foundation bearing capacity detection with engineering geological conditions, it takes on preferable promise for further gain.