Research On Reinforcement Mechanism Of Pile Shaft Grouting And Test Study

Pile shaft grouting, emerging as a form of technology in recent years, of which the mechanism of improving shaft friction still remains unidentified. Therefore, indoor multi-scale testing, on-site real-time monitoring as well as practical engineering research in such areas as comparative examples.The stress level of pile foundation subjected to lateral soil extrusion has significant influence on piles ultimate settlement especially for those constructed in over-consolidated soils. Through analysis of the role of lateral stress played in re-settlement of piles in over-consolidated soils, the settlement formula is obtained and the corresponding analytical solution is given.Indoor testing of remolded soil samples with different cement mixing ratio is conducted. Through comparison of soil samples with a certain cement mixing ratio and none, samples with different cement mixing ratio as well as cemented soil samples and grouted soil samples in practical engineering in use of SEM, great difference is found in meso-structure of soil samples after the mixing of cement in that the cementation level of soil particles improves with cement mixing dosage and that the cementation degree of practical grouted samples goes higher than those remolded samples hence meso-evidence of soil parameters change by pile shaft grouting is presented.Direct shear test of different types of soil, soil with different cement dosage and interface shear test of soil and cemented soil indicate that soil-cement interface shear strength of the shear and the incorporation of indicators as the volume of cement obviously change, but the growth rate of interfacial shear indicators is smaller than the corresponding indicators of soil-cement; With the increase of dosage of cement, cement forms of soil shear failure damage transits from plastic to brittle.Through real-time grouting pressure monitoring of 361 grouted piles in a certain project in Wenzhou, five types of pressure to time curves are generalized. In the same time, pertinence cause of each type and the corresponding problems that need attention during the grouting process are brought forward. Besides, analysis of affecting factors of opening pressure and end grouting pressure is conducted, and derived the conclusion that pile age has a great influence on the opening pressure, while almost no on the end grouting pressure.By case study of a major anti-floating engineering project in Shanghai, comparison of uplifting performance between belled uplift piles and shaft grouting piles indicates that the performance of pile grouting pile is better than belled anti-pull piles considering the indicators of pile end displacement and pile top displacement under the design uplift capacity and the dispersion degree of bearing capacity.