| Pile foundation is a common and reliable form of foundation and is widely used in civil engineering.It has the advantages of high strength,high bearing capacity and good durability,and can effectively support buildings and other structural systems.When a pile foundation is buried in the soil,the pile will form an interaction system with the soil,resulting in a bonding effect,which has a significant impact on the mechanical properties,stability and load-bearing capacity of the pile.However,as the mechanism of pile-soil bonding is relatively complex and involves a variety of factors,such as soil type,pile shape and load action,there is no unified theoretical model to completely describe the behaviour of pile-soil bonding.Traditional pile-soil bond monitoring methods mainly rely on qualitative or quantitative analysis based on experience,such as pile lateral resistance calculation methods,pile displacement methods,etc.These methods have major limitations in terms of accuracy and sensitivity,and are difficult to meet the monitoring requirements in complex engineering environments.In recent years,piezoelectric ceramic sensors have been widely used in the field of structural health monitoring due to their advantages of simple fabrication process,good durability,anti-interference,high sensitivity and low cost.In this research context,this paper further investigates the method of pile-soil bond condition monitoring based on the fluctuation analysis method.The method provides a potential approach to directly assess the safety of piles.Details of the research are as follows:(1)Introduction of the monitoring principle of the test as well as the method and process of fabricating embedded piezoelectric smart aggregate and reinforced concrete test piles.Multiple piezoelectric smart aggregates were embedded in the column as sensors to receive signals,and transient horizontal load excitation was applied by a hammer.The pile-soil bond state monitoring was carried out by fluctuation analysis based on piezoelectric ceramics to investigate the effects of pile-soil stripping,differences in soil state and freeze-thaw cycles on the pile-soil bond state.The test results show that pile-soil stripping damage leads to a weakening of the bonding effect and the time domain amplitude of the received signal becomes smaller and more pronounced as the depth and extent of the crack increases.Soil confinement has a significant effect on the attenuation of the fluctuating signal.An increase in soil density increases the pile-soil bonding action and reduces the fluctuating response of the pile foundation.In the case of soil stratification based on different densities,decreasing the density of the upper soil layer will reduce the pile-soil bonding action,which will lead to an increase in the fluctuating response of the pile.Secondly,the mechanical properties of the soil under freeze-thaw cycling not only change with temperature but also with water content,both of which lead to changes in the binding force of the soil on the pile and thus affect the pile-soil bond.(2)The experimental models of pile-soil stripping and different soil states were established by ABAQUS finite element software to simulate the bond state between pile foundation and soil under horizontal transient excitation,and to obtain the law of pile-soil contact stress distribution,thus verifying that the law is consistent with the experimental results,and further proving the feasibility of the study of pile-soil bond state monitoring based on piezoelectric ceramic sensors. |
