Experimental study on seismic reinforcement of bridge foundation on silty clay landslide with inclined interlayer

A shaking table test for a bridge foundation reinforced by anti-slide piles on a silty clay landslide model with an inclined interlayer was performed.The deformation characteristics of the bridge foundation piles and anti-slide piles were analyzed in different loading conditions.The dynamic response law of a silty clay landslide with an inclined interlayer was summarized.The spacing between the rear anti-slide piles and bridge foundation should be reasonably controlled according to the seismic fortification requirements,to avoid the two peaks in the forced deformation of the bridge foundation piles.The“blocking effect”of the bridge foundation piles reduced the deformation of the forward anti-slide piles.The stress-strain response of silty clay was intensified as the vibration wave field appeared on the slope.Since the vibration intensified,the thrust distribution of the landslide underwent a process of shifting from triangle to inverted trapezoid,the difference in the acceleration response between the bearing platform and silty clay landslide tended to decrease,and the spectrum amplitude near the natural vibration frequency increased.The rear anti-slide piles were able to slow down the shear deformation of the soil in front of the piles and avoid excessive acceleration response of the bridge foundation piles.

Discussion on Construction Technology of Subway Tunnel Expansion under Bridge Foundation

As the urban populations grow,the number and size of subway construction projects are increasing while also meeting higher construction standards.So,subway construction projects must have a better understanding of construction technology.This article focuses on the construction technology of the subway tunnel expansion under the bridge foundation.By analyzing the engineering characteristics of the bridge foundation and using a project as an example,this article provides a detailed discussion of the construction process of tunnel expansion under a bridge foundation.This article aims to serve as a reference for subway tunnel construction in China to ensure the key points of construction technology are understood,thus improving construction quality and laying a solid technical foundation for the sustainable development of urban rail engineering.

Construction Technology of Pile Foundation for Subway Tunnel Crossing Bridge

Urban infrastructure has become more complex with the rapid development of urban transportation networks.In urban environments with limited space,construction of facilities like subways and bridges may mutually influence each other,especially when subway construction requires passing under bridges.In such cases,pile foundation replacement technology is often necessary.However,this technology is highly specialized,with a lengthy and risky construction period,and high costs.Personnel must be proficient in key technical aspects to ensure construction quality.This article discusses the technical principle,construction process,and core technology of pile foundation replacement,along with the application of this technology in subway tunnel crossing bridge projects,supported by engineering examples for reference.

The behavior of a rectangular closed diaphragm wall when used as a bridge foundation

The rectangular closed diaphragm(RCD)wall is a new type of bridge foundation.Compared to barrette foundation,measuring the performance of RCD walls is relatively complicated because of their incorporation of a soil core.Using the FLAC3D software,this paper investigates the deformation properties,soil resistance and skin friction of a laterally loaded RCD wall as well as the settlement,axial force and load-sharing ratio of a vertically loaded RCD wall.Special attention is given to the analysis of factors that influence the performance of the soil core.It was found that under lateral loading,the RCD wall behaves as an end-bearing friction wall during the entire loading process.The relative displacement between the wall body and the soil core primarily occurs below the rotation point,and the horizontal displacement of the soil core is greater than that of the wall body.Under vertical loading,the degree of inner skin friction around the bottom of the soil core and the proportion of the loading supported by the soil core increase with increased cross-section size.The wall depth is directly proportional to the loading supported by the outer skin friction and the tip resistance of the wall body and is inversely proportional to the loading borne by the soil core.

Influencing factors and control measures of excavation on adjacent bridge foundation based on analytic hierarchy process and finite element method

Many uncertain factors in the excavation process may lead to excessive lateral displacement or overlimited internal force of the piles,as well as inordinate settlement of soil surrounding the existing bridge foundation.Safety control is pivotal to ensuring the safety of adjacent structures.In this paper,an innovative method is proposed that combines an analytic hierarchy process(AHP)with a finite element method(FEM)to reveal the potential impact risk of uncertain factors on the surrounding environment.The AHP was adopted to determine key influencing factors based on the weight of each influencing factor.The FEM was used to quantify the impact of the key influencing factors on the surrounding environment.In terms of the AHP,the index system of uncertain factors was established based on an engineering investigation.A matrix comparing the lower index layer to the upper index layer,and the weight of each influencing factor,were calculated.It was found that the excavation depth and the distance between the foundation pit and the bridge foundation were fundamental factors.For the FEM,the FE baseline model was calibrated based on the case of no bridge surrounding the foundation pit.The consistency between the monitoring data and the numerical simulation data for a ground settlement was analyzed.FE simulations were then conducted to quantitatively analyze the degree of influence of the key influencing factors on the bridge foundation.Furthermore,the lateral displacement of the bridge pile foundation,the internal force of the piles,and the settlement of the soil surrounding the pile foundation were emphatically analyzed.The most hazardous construction condition was also determined.Finally,two safety control measures for increasing the numbers of support levels and the rooted depths of the enclosure structure were suggested.A novel method for combining AHP with FEM can be used to determine the key influencing aspects among many uncertain factors during a construction,which can provide some beneficial references for engineering design and construction.

Diaphragm wall-soil-cap interaction in rectangular-closed-diaphragm-wall bridge foundations

Rectangular-closed-diaphragm-wall foundation is a new type of bridge foundation.Diaphragm wallsoil-cap interaction was studied using a model test.It was observed that the distribution of soil resistance under the cap is not homogeneous.The soil resistance in the corner under the cap is larger than that in the border;and that in the center is the smallest.The distribution of soil resistance under the cap will be more uniform,if the sectional area of soil core is enlarged within a certain range.Due to the existence of cap,there is a“weakening effect”in inner shaft resistance of the upper wall segments,and there is“enhancement effect”in the lower wall segments and in toe resistance.The load shearing percentage of soil resistance under the cap is 10%–20%.It is unreasonable to ignore the effects of the cap and the soil resistance under the cap in bearing capacity calculations.

Study on the Safety of the Foundation Rock Masses in the Tangkou Bank of the Taipinghu Bridge

The Taipinghu Bridge is an important project, and the safety of rock masses of its foundation is very crucial. This article analyzes the potential causes of the deformation of the rock masses of the bridge foundation, and uses the Fast Lagrangian Analysis of Continua to analyze the geologic model. The simulating process shows that no mater in the excavating process or in the loading process the rock masses are suit for the engineering. The modeling and analyzing process can be used for reference.

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.

Time-dependent deviation of bridge pile foundations caused by adjacent large-area surcharge loads in soft soils and its preventive measures

Time-dependent characteristics(TDCs)have been neglected in most previous studies investigating the deviation mechanisms of bridge pile foundations and evaluating the effectiveness of preventive measures.In this study,the stress-strain-time characteristics of soft soils were illustrated by consolidation-creep tests based on a typical engineering case.An extended Koppejan model was developed and then embedded in a finite element(FE)model via a user-material subroutine(UMAT).Based on the validated FE model,the time-dependent deformation mechanism of the pile foundation was revealed,and the preventive effect of applying micropiles and stress-release holes to control the deviation was investigated.The results show that the calculated maximum lateral displacement of the cap differs from the measured one by 6.5%,indicating that the derived extended Koppejan model reproduced the deviation process of the bridge cap-pile foundation with time.The additional load acting on the pile side caused by soil lateral deformation was mainly concentrated within the soft soil layer and increased with the increase in load duration.Compared with t=3 d(where t is surcharge time),the maximum lateral additional pressure acting on Pile 2#increased by approximately 47.0%at t=224 d.For bridge pile foundation deviation in deep soft soils,stress-release holes can provide better prevention compared to micropiles and are therefore recommended.

Three-dimensional elasto-plastic finite element analysis of a soil-pilebridge interaction

The soil-pile-bridge interaction of super-large pile groups is a very complex issue for the design of deep pile group foundations. In this paper, the load distribution on the pile top of a super large bridge foundation and its influential factors are analyzed comprehensively using a three-dimensional elasto-plastic finite element method. The adopted model and its input parameters are firstly verified by comparing the numerical results with the measured data of static loading tests of a single pile. Numerical analysis is then performed to investigate the load distribution and the load-settlement characteristics of super-large pile groups, and the models are verified using centrifuge laboratory model testing data. The mechanism of the interaction between pile groups and soil under different conditions is explored.

A Research on the Behavior of a Polyurethane Polymer Waterproof Material Used in Bridge Geotechnical Applications

Polyurethane is enjoying a widespread use as a polymer-based waterproof material in civil engineering In the present study we consider a temperature-sensitive waterproof and moisture-permeable polyurethane material(PTPE-PU)characterized by one or more phase transition temperatures(critical temperatures).Near the critical temperature,the waterproof and moisture permeability of polyurethane undergo abrupt changes.The related stability,thermal performance,water resistance,hydrostatic pressure,and moisture permeability are investigated here considering a PTPE-PU traditionally used in bridge geotechnical engineering.The results show that the moisture permeability of the coated bridge rock and soil undergo sudden variations near the crystallization and melting temperature of the soft segment.The moisture permeability is 3000 g/(m^(2)d).The hydrostatic pressure of the coated bridge rock and soil is 3.5 kPa.

Study on the Safety of the Rock Mass in the Tongling Bank of Taipinghu Bridge

The Taipinghu Bridge is an important engineering construction, and the safety of rock mass of its foundation is very crucial. This article adopts FLAC 3D to analysis the geologic model. The simulating process shows that no mater the excavating process or the loading process the rock mass are safe. The modeling and analyzing process can be used for reference.

Numerical modeling of current-induced scour around multi-wall foundation using large-eddy simulation

Scouring is one of the primary triggers of failure for bridges across rivers or seas.However,research concerning the scour mechanism of multi-wall foundations(MWFs)remains scarce,hindering the further application of MWFs.In this study,for the first time,the scouring effect caused by unidirectional flow around MWFs was examined numerically using FLOW-3D involving a large-eddy simulation.Initially,the applicability of the scouring model and input parameters was validated using a case study based on published measured data.Subsequently,the scouring effects of four MWFs with different wall arrangements and inflow angles,including the flow field analysis and scour pit and depth,were investigated thoroughly.It was found that the maximum scour depth of MWFs with an inflow angle of 0°was smaller than that of those with an inflow angle of 45°,regardless of the wall arrangement.Meanwhile,changing the inflow angle significantly affects the scour characteristics of MWFs arranged in parallel.In practical engineering,MWFs arranged in parallel are preferred considering the need for scouring resistance.However,a comparative analysis should be performed to consider comprehensively whether to adopt the form of a round wall arrangement when the inflow angle is not 0°or the inflow direction is changeable.

Numerical simulation and analysis of the pile underpinning technology used in shield tunnel crossings on bridge pile foundations

Currently,the pile foundation underpinning technology is widely used when underground transportation infrastructure passes through existing buildings or structures in urban areas.This study aims to investigate stress transfer mechanisms in pile foundations during an underpinning process as well as the influence of shield tunnel construction on pile stability.To this end,the pile foundation underpinning technology used in China’s Shenzhen Metro Line 10 crossing through the bridge pile foundation group of the Guangzhou-Shenzhen highway was analyzed in detailed.The refined numerical simulation of the pile foundation underpinning and shield tunnel construction processes were conducted using the fast Lagrangian analysis of continua in 3 dimensions(FLAC3D)software.The results demonstrate that after the pile foundation underpinned,the previous bridge load system of bridge panel→pile foundation→bearing soil would transform into a bridge panel→existing pile foundation→new underpinning pile→deep bearing soil stratum structure.The overlying load on the underpinned pile could be effectively transferred to a new underpinning pile.In the process of underpinning and tunnel excavation,the settlement and deformation of the foundation can improve the tip resistance and shaft friction of piles,which in turn,can reduce the maximum principal stress in the pile foundation group.The deformation of the bridge pile foundation is mainly caused by ground loss and excavation disturbance generated during shield tunneling as the settlement induced by pile foundation underpinning accounts for approximately 20%-30% of the total settlement.The reduction effects of settlement deformation,lateral displacement,and principal stress are mainly manifested in underpinning piles,while the non-underpinning pile exhibits minimal variation.Meanwhile,the deformation of the segment lining structure of the shield tunnel primarily occurs near the underpinning area of the pile foundation,and it is mainly settlement deformation with a small horizontal displacement.