Wireless remote spatiotemporal monitoring of high-fill foundation deformation

The spatial and temporal deformation patterns and deformation control indicators of highfill foundations directly affect the design,construction and operational safety of high-fill projects.In situ monitoring can comprehensively reflect the deformation of high-fill during and after construction.In this paper,we have first designed and installed an integrated wireless remote monitoring system for high-fill to achieve real-time dynamic monitoring of settlement,pore water pressure and soil pressure of the fill foundation.Based on the monitoring results of nearly one year of the construction period and two years after construction,it was found that the deformation amount and deformation rate of the high-fill foundation showed a non-linear growth relationship with the filling rate and filling height.The settlement deformation of the high-fill foundation during the loading period was mainly dominated by the original foundation soil,accounting for 54.4%of the total settlement on average;the settlement deformation during the post-construction period was mainly dominated by the filling body,accounting for 77.04%of the total settlement on average,and the settlement deformation during the post-construction period mainly occurred in the first year after construction.The analysis of the deformation mechanism suggests that the deformation of the filling body is dominated by exhaust consolidation during the loading period and drainage consolidation during the post-construction period;the deformation of the original foundation soil is dominated by drainage consolidation during the loading period and drainage consolidation develops slowly during the post-construction period.It is recommended that the original foundation should be reinforced before the large area filling construction,and that the filling rate should be strictly controlled during construction.The research results can provide a scientific basis for deformation calculation and stability assessment of high-fill foundations.

Effects of liquefaction-induced large lateral ground deformation on pile foundations

The pile-soil system interaction computational model in liquefaction-induced lateral spreading ground was established by the finite difference numerical method.Considering an elastic-plastic subgrade reaction method,numerical methods involving finite difference approach of pile in liquefaction-induced lateral spreading ground were derived and implemented into a finite difference program.Based on the monotonic loading tests on saturated sand after liquefaction,the liquefaction lateral deformation of the site where group piles are located was predicted.The effects of lateral ground deformation after liquefaction on a group of pile foundations were studied using the fmite difference program mentioned above,and the failure mechanism of group piles in liquefaction-induced lateral spreading ground was obtained.The applicability of the program was preliminarily verified.The results show that the bending moments at the interfaces between liquefied and non-liquefied soil layers are larger than those at the pile＇s top when the pile＇s top is embedded.The value of the additional static bending moment is larger than the peak dynamic bending moment during the earthquake,so in the pile foundation design,more than the superstructure＇s dynamics should be considered and the effect of lateral ground deformation on pile foundations cannot be neglected.

Research of deformation prediction method of soft soil deep foundation pit

In view of the characteristics of soft soil deep foundation pit for the construction and geotechnical characteristics of the special medium,it is difficult to calculate theoreti- cally accurately structural deformation of the foundation pit,so in the course of excavation on the construction of the information is particularly important.The analysis and compari- son of several popular non-linear forecasting methods,combined with the actual projects, set up a grey theoretical prediction model,time series forecasting model,improved neural network model to predict deformation of the foundation pit.The results show that the use of neural network to predict with high accuracy solution,it is the foundation deformation prediction effective way in underground works with good prospects.

Study on Deformation Law of Circular Foundation Under Combined Loading

The foundations of some ocean engineering structures are built to withstand not only the vertical gravity load V, but also the horizontal load H induced by sea waves and current. The horizontal load includes the concentrated force load, the moment load M, and the torque load T termed also as combined loading. It is of academic and engineering significance to study the deformation law of submarine seabed due to combined loading. On the basis of the three-dimensional elastic mechanics solution of circular foundation, numerical methods are used to analyze the deformation law of submarine soil under circular foundation with six degrees of freedom. The finite element analysis results give the elastic deformation law of soil in three dimensional spaces, modify the theoretical elasticity solution, and presents nonlinear soil deformation mechanism under the circular foundation with six degrees of freedom.

Deformation and failure modes of composite foundation with sub-embankment plain concrete piles

With the development of high-speed railway in China, composite foundation with rigid piles has become a stamdard solution of meeting the high requirements of stability and post-construction settlement of embankment on soft subgrade. Among several im- provement pattems, plain concrete piles have been extensively used to treat soft ground supported embankment. To investigate the deformation and failure modes of unimproved soft ground and soft ground reinforced by sub-embankment plain concrete piles, and to learn the influences of track and vehicle load, the effect of pile spacing, as well as the compression moduli of soil layers and upper load condition on the failure modes, a series of centrifuge model tests were performed. Test results indicate that the dis- placement of unimproved soft ground under the embankment increases continuously as embankment, track and train loading, and slip circle failure takes place. The deformation law of soft ground reinforced by sub-embankment plain concrete piles depends on pile spacing, compression modulus of the soft ground, and loading conditions. It was also found that plain concrete piles show displacement and failure patterns depending on its location, compression modulus of soft soil around the pile, and loading condi- tions. Furthermore, the evaluation of improved ground stability as well as the model test procedure is also presented.

Research on Deformation and Force of Bridge Pile Foundation on High and Steep Slope in Mountainous Area

With the rapid development of my country’s economy, the demand for infrastructure construction is also increasing. However, in most areas of China, the terrains are mountainous and hilly. Some projects have to be built on steep slopes. Choosing viaducts or half-bridges on high-steep slopes is not only conducive to the protection of the surrounding environment, but also conducive to the stability of the slope. Bridges usually choose the form of pile foundation-high pier bridge. This paper uses numerical simulation to study and analyze the bridge pile foundation of the slope section. Relying on actual engineering, use the finite element software ABAQUS6.14 to establish a three-dimensional finite element model to study the bearing mechanism and mechanical characteristics of the pile foundation under vertical load, horizontal load and inclined load, discuss the influence of the nature of the soil around the pile and the stiffness of the pile body on the deformation and internal force of the bridge pile foundation in the slope section. The analysis results show that the horizontal load has a great influence on the horizontal displacement of the pile, but has a small influence on the vertical displacement, and the vertical load is just the opposite. Inclined load has obvious “p-Δ” effect. The increase in soil elastic modulus and pile stiffness will reduce the displacement of the pile foundation, but after reaching a certain range, the displacement of the pile foundation will tend to be stable. Therefore, in actual engineering, if the displacement of the pile foundation fails to meet the requirements, the hardness of the soil and the stiffness of the pile can be appropriately increased, but not blindly.

Prediction Method of Seismic Residual Deformation of Caisson Quay Wall in Liquefied Foundation

The multi-spring shear mechanism plastic model in this paper is defined in strain space to simulate pore pressure generation and development in sands under cyclic loading and undrained conditions, and the rotation of principal stresses can also be simulated by the model with cyclic behavior of anisotropic consolidated sands. Seismic residual deformations of typical caisson quay walls under different engineering situations are analyzed in detail by the plastic model, and then an index of liquefaction extent is applied to describe the regularity of seismic residual deformation of caisson quay wall top under different engineering situations. Some correlated prediction formulas are derived from the results of regression analysis between seismic residual deformation of quay wall top and extent of liquefaction in the relative safety backfill sand site. Finally, the rationality and the reliability of the prediction methods are validated by test results of a 120 g-centrifuge shaking table, and the comparisons show that some reliable seismic residual deformation of caisson quay can be predicted by appropriate prediction formulas and appropriate index of liquefaction extent.

Estimation of Heights of Soil Plug Inside Bucket Foundations During Suction Penetration by Deformable Discrete Element Modeling

The soil plug phenomenon involving the rising of the surface soil inside the bucket chamber under the suction pressure and seepage forces was simulated and calculated by deformable discrete element method (DDEM) models. The seepage forces, the effective gravity of soil, the friction on the chamber wall and the suction inside the chamber are considered as the main external forces of DDEM specimen. Three typical types of soil (silty clay, silt and sand) in the Bohai Sea are set as the main environmental conditions in the formation process of soil plug. It is found that the heights of soil plug simulated by DDEM models are 161.85 mm in silty clay, 125.22 mm in silt and 167.56 mm in sand, which are close to model test results and higher than those estimated by discrete element method (DEM). DDEM is an effective method to estimate and predict the heights of soil plug before suction penetration of bucket foundations on site.

Buckling analysis of shear deformable composite conical shells reinforced by CNTs subjected to combined loading on the two-parameter elastic foundation

The main objective of this study is to investigate the buckling analysis of CCSs reinforced by CNTs subjected to combined loading of hydrostatic pressure and axial compression resting on the twoparameter elastic foundation(T-P-EF).It is one of the first attempts to derive the governing equations of the CCSs reinforced with CNTs,based on a generalized first-order shear deformation shell theory(FSDST)which includes shell-foundation interaction.By adopting the extended mixing rule,the effective material properties of CCSs reinforced by CNTs with linear distributions are approximated by introducing some efficiency parameters.Three carbon nanotube distribution in the matrix,i.e.uniform distribution(U)and V and X-types linear distribution are taken into account.The stability equations are solved by using the Galerkin procedure to determine the combined buckling loads(CBLs)of the structure selected here.The numerical illustrations cover CBLs characteristics of CCSs reinforced by CNTs in the presence of the T-P-EF.Finally,a parametric study is carried out to study the influences of the foundation parameters,the volume fraction of carbon nanotubes and the types of reinforcement on the CBLs.

Feasibility of columnar jointed basalt used for high-arch dam foundation

Columnar jointed basalt, with a lot of small-spacing structural planes and poor integrity, is a kind of fractured rock mass. Through comprehensive study of columnar joints shape, roughness of fracture surface and chemical composition of basalt, it is known that columnar joints of Baihetan dam area were formed as a result of cooling and shrinkage effects of magma. The columnar jointed basalt is mainly formed through chemical reaction of chlorite, kaolinite, epidote and tremolite, and the columnar joints mainly consist of chlorite according to slice identification and chemical analysis. Test results show that the columnar jointed basalt has high uniaxial compressive strength, low friction coefficient, and high cohesion, shear strength and deformation index. Meanwhile, the columnar jointed basalt is closely locked, and joint surfaces are well closed. The permeability of the rock is quite weak, and the P-wave velocity in the rock could get up to 5 000 m/s. All these show good rock properties. The columnar joints develop regularly, different from the general fractured rock masses. In summary, the columnar jointed basalt can be used directly as a foundation of dam.

Methods of configuration test and deformation analysis for large airship

In recent years, high-altitude aerostats have been increasingly developed in the direction of multi-functionality and large size. Due to the large size and the high flexibility, new challenges for large aerostats have appeared in the configuration test and the deformation analysis. The methods of the configuration test and the deformation analysis for large airship have been researched and discussed. A tested method of the configuration,named internal scanning, is established to quickly obtain the spatial information of all surfaces for the large airship by the three-dimensional(3D) laser scanning technology. By using the surface wrap method, the configuration parameters of the large airship are calculated. According to the test data of the configuration, the structural dimensions such as the distances between the characteristic sections are measured. The method of the deformation analysis for the airship contains the algorithm of nonuniform rational B-splines(NURBS) and the finite element(FE)method. The algorithm of NURBS is used to obtain the reconfiguration model of the large airship. The seams are considered and the seam areas are divided. The FE model of the middle part of the large airship is established. The distributions of the stress and the strain for the large airship are obtained by the FE method. The position of the larger deformation for the airship is found.

Settlement of composite foundation with discrete material pile considering modulus change

Based on deeply discussing the deformation mechanism of composite foundation with discrete material pile, firstly, the settlement of composite foundation in rigid foundation conditions was assumed to consist of two parts, an expanding part and an un-expanding part. Then, in view of the differences of deformation properties between the expanding part and the un-expanding part, the relationships between the pile modulus and the applied load in these two parts were respectively developed. Thirdly, by introducing the above relationships into settlement analysis, a new method to calculate displacement of composite foundation with discrete material pile was proposed by using the multi-stage loading theory and the layer-wise summation approach. This method is effective not only for accounting for the effect of variations of pores on deformation modulus of the pile body in different depths, but also for describing the characteristics of different deformation mechanisms of the pile body with varying depth. Finally, the proposed method was used to a practical composite foundation problem, whose theoretical results were presented and compared to those of other methods. The rationality and feasibility of this method are identified through comparative analysis.

GENERAL SOLUTION FOR LARGE DEFLECTION PROBLEMS OF NONHOMOGENEOUS CIRCULAR PLATES ON ELASTIC FOUNDATION

A new method was presented here based on authors' previous work. This new method can be used to solve the arbitrary nonlinear system of differential equations with variable coefficients. By this method, the general solution for large deformation of nonhomogeneous circular plates resting on a elastic foundation was derived, and its convergence was proved. Finally, the only thing necessary to solve is a set of nonlinear algebraic equations with three unknowns. The solution obtained by the present method has large convergence range and the computation is simpler and more rapid than other numerical methods. The numerical examples indicate that satisfactory results of stress resultants and displacements can be obtained by the present method. The correctness of the theory in this paper has been confirmed.

An Improved Model for Bending of Thin Viscoelastic Plate on Elastic Foundation

An improved model for bending of thin viscoe-lastic plate resting on Winkler foundation is presented. The thin plate is linear viscoelastic and subjected to normal distributed loading, the effect of normal stress along the plate thickness on the deflection and internal forces is taken into account. The basic equations for internal forces and stress distribution are derived based on the general viscoelastic theory under small deformation condition. The reduced equations for elastic case are given as well. It is shown that the proposed model reveals a larger flex-ural rigidity compared to that in classic models, in which the normal stress along the plate thickness is neglected.

Bending and stress analysis of polymeric composite plates reinforced with functionally graded graphene platelets based on sinusoidal shear-deformation plate theory

The bending and stress analysis of a functionally graded polymer composite plate reinforced with graphene platelets are studied in this paper.The governing equations are derived by using principle of virtual work for a plate which is rested on Pasternak’s foundation.Sinusoidal shear deformation theory is used to describe displacement field.Four different distribution patterns are employed in our analysis.The analytical solution is presented for a functionally graded plate to investigate the influence of important parameters.The numerical results are presented to show the deflection and stress results of the problem for four employed patterns in terms of geometric parameters such as number of layers,weight fraction and two parameters of Pasternak’s foundation.

Soil bentonite wall protects foundation from thrust faulting: analyses and experiment

When seismic thrust faults emerge on the ground surface, they are particularly damaging to buildings, bridges and lifelines that lie on the rupture path. To protect a structure founded on a rigid raft, a thick diaphragm-type soil bentonite wall （SBW） is installed in front of and near the foundation, at sufficient depth to intercept the propagating fault rupture. Extensive numerical analyses, verified against reduced-scale （1 g） split box physical model tests, reveal that such a wall, thanks to its high deformability and low shear resistance, ＂absorbs＂ the compressive thrust of the fault and forces the rupture to deviate upwards along its length. As a consequence, the foundation is left essentially intact. The effectiveness of SBW is demonstrated to depend on the exact location of the emerging fault and the magnitude of the fault offset. When the latter is large, the unprotected foundation experiences intolerable rigid-body rotation even if the foundation structural distress is not substantial.

Free Vibration Analysis of FG-CNTRC Cylindrical Pressure Vessels Resting on Pasternak Foundation with Various Boundary Conditions

This study focuses on vibration analysis of cylindrical pressure vessels constructed by functionally graded carbon nanotube reinforced composites(FG-CNTRC).The vessel is under internal pressure and surrounded by a Pasternak foundation.This investigation was founded based on two-dimensional elastic analysis and used Hamilton’s principle to drive the governing equations.The deformations and effective-mechanical properties of the reinforced structure were elicited from the first-order shear theory(FSDT)and rule of mixture,respectively.The main goal of this study is to show the effects of various design parameters such as boundary conditions,reinforcement distribution,foundation parameters,and aspect ratio on the free vibration characteristics of the structure.

Numerical Study of the Mechanical Behavior of a Foundation Raft under the Hydrodynamic Influence of the Mechanical Characteristics of Clay Soils

The clay soils of the city of Douala are constantly saturated with water, which permanently favors the hydrodynamic behavior of the soils (swelling or consolidation). This phenomenon can cause serious disturbances in the structure of buildings resulting in the appearance of cracks in structures (buildings, road bridge, viaduct, etc.). The foundation raft is a very important structure in the dimensioning of structures. Given the soil-structure interactions, its mechanical characteristics must be the subject of a special study linked to the building environment. In this article, we present a study of the mechanical behavior of a foundation raft anchored in a laminate floor. The aim is to highlight the influence of the mechanical properties of the foundation soil on the evolution of the mechanical behavior of the raft. The method used is a numerical simulation. A physical model taking into account a 5-storey building based in Douala in the Denver district is studied. The foundation on the raft foundation of this building follows an elastic constitutive law with Mazars damage, and rests on a laminated soil of plastic elastic model with Camclay plasticity criterion. The ground-raft and ground-ground interfaces are carried out with the finite elements joined to three nodes (JOI3), and obey the Coulomb model;it is an expansion joint model with Mohr-Coulomb type criterion and associated flow. The numerical resolution is carried out by the finite element method, and the numerical simulations via the Cast3M calculation code. The results from the simulations show that the mechanical characteristics of foundation soils, in this case the water content, the compactness, the state of consolidation, greatly influence the mechanical behavior of the foundation slab. There is indeed a significant settlement and a great deformation of the raft foundation when the water content of the soil layers increases, and when the states of consolidation and compactness are low. This article allows us to predict and control the evolution of the behavior of the ground-structure interface of a raft foundation and to adopt a new model appropriate for the sizing of civil engineering structures.

Free-Form Laminated Doubly-Curved Shells and Panels of Revolution Resting on Winkler-Pasternak Elastic Foundations: A 2-D GDQ Solution for Static and Free Vibration Analysis

This work presents the static and dynamic analyses of laminated doubly-curved shells and panels of revolution resting on Winkler-Pasternak elastic foundations using the Generalized Differential Quadrature (GDQ) method. The analyses are worked out considering the First-order Shear Deformation Theory (FSDT) for the above mentioned moderately thick structural elements. The effect of the shell curvatures is included from the beginning of the theory formulation in the kinematic model. The solutions are given in terms of generalized displacement components of points lying on the middle surface of the shell. Simple Rational Bézier curves are used to define the meridian curve of the revolution structures. The discretization of the system by means of the GDQ technique leads to a standard linear problem for the static analysis and to a standard linear eigenvalue problem for the dynamic analysis. Comparisons between the present formulation and the Reissner-Mindlin theory are presented. Furthermore, GDQ results are compared with those obtained by using commercial programs. Very good agreement is observed. Finally, new results are presented in order to investtigate the effects of the Winkler modulus, the Pasternak modulus and the inertia of the elastic foundation on the behavior of laminated shells of revolution.

盾构隧道近接斜交侧穿桥梁桩基变形计算方法

以圆形截面桩为例,基于修正后的Loganathan公式,利用文克尔弹性地基梁模型、m法计算理论和荷载传递法,建立盾构隧道近接斜交侧穿既有桥梁桩基的变形计算方法.通过现场监测结果验证计算方法的工程适用性,并利用该方法分析侧穿桥梁桩基施工引起桩身水平挠曲变形的主要影响因素.结果表明:桩身水平位移和桩顶竖向位移的理论计算结果与监测结果之间的最大误差分别不超过14.6%和2.7%.与现有方法相比,所提方法的计算结果更接近实测值.入土段桩身水平挠曲程度与隧道轴心和桩基中心轴线之间的水平距离、隧道侧穿斜交角呈负相关;最大水平挠曲位移与隧道侧穿斜交角呈负相关.当水平侧穿距离为6.0 m时,最大水平挠曲变形为7.4 mm;当隧道盾构侧穿斜交角为70.0°时,入土段桩身最大水平挠曲位移为15.4 mm.