Study On Stress And Deformation Of The Rubble-bedding Foundation In Deep Trench For Gravity Quays

The construction of deep-water berth wharf has become an inevitable choice for the future development of port.However,there are still some problems in the design and construction of the ultra-deep foundation trench gravity quays.For example,optimizing the foundation size and solving the over cost problems by analyzing the stress conditions of the base and the foundation bed,and calculating the settlement and deformation in the later period of wharf.In this paper,mechanism experiment,numerical simulation analysis and design calculation methods are used to study the stress and deformation of riprap bed of deep foundation gravity wharf.First of all,the cracking and deformation of edges of rock are studied by using mechanism test.It was found that the composite of stone particles of different weight changed in different degrees after the compression test.Specifically the ratio of large particles decreased while the ratio of small particles increased significantly.It fully proves that the rock sample was broken by the load.Then,the compression characteristics and deformation parameters of the rubble-bedding of gravity quays are investigated by prototype compression test.The stress-strain curves and deformation parameters are finally obtained from combined experimental and finite element analysis.The Poisson’s ratio of the block stones can be assumed as a constant between 0.2 and 0.3.The compressive deformation modulus depend on the numbers of loading and unloading.Denoted as three compression modulus parameters of initial loading,secondary loading and multiple loading according to the value range.The stress-strain curve of the block stones in the rubble-bedding of gravity quays can be described piecewise by the corresponding modulus of compression according to the loading times of segmented load stress.Furthermore,according to the results of the experiment,a finite element model of background engineering is established.And the numerical result is verified by the measured data.According to the results of numerical simulation,the stress distribution laws of the rubble-bedding in ultra-deep foundation trench gravity quays is summarized.Stresses are mainly propagated downward in the rubble-bedding.The maximum stress of the rubble-bedding is not within the slope line of 1:1～1:1.5 on the front side of the front toe,but directly below the caisson.And the maximum moves from the front toe to the back toe with the increase of depth.Then the effects of various factors on the vertical stress and displacement of the rubble-bedding are studied by numerical simulation.The width of the foundation trench has a relatively large impact on the vertical stress,the smaller the width the greater the stress below the front toe.But the maximum value of stress is basically the same,when the the rubble-bedding has different widthes.Furthermore,the elastic modulus of rock and the elastic modulus of soil below the foundation trench have a great effect on the vertical displacement of the rubble-bedding.The maximum displacement decreases with the increase of elastic modulus.Finally,based on the study of the stress distribution of the rubble-bedding,an improved algorithm of stress is proposed.The stress at the top of the rubble-bedding is divided into three parts and is diffused respectively.The total additional stress can be obtained by superimposing the additional stress at each feature point,and then add it to the self-weight stress to get the vertical stress of the rubble-bedding.Based on the calculation of engineering cases,it is found that the improved calculation method can reflect the actual distribution of the stress of the rubble-bedding more accurately.According to the study of the stress distribution of the rubble-bedding,the size of the rubble-bedding is optimized.Adopting the rubble-bedding after optimization can greatly reduce the work of excavation and the amount of rock.