Bridge Foundations Research Articles

Detection of karst voids at pile foundation by full-waveform inversion of single borehole sonic data

Drilled boreholes are commonly used to detect rock voids and fractures in underground construction projects such as pile foundations, tunnel borings, and other near surface human activities. However, voids can be missed by direct drilling due to their limited size. Borehole sonic sounding can be used to image voids in the vicinity of the borehole. We developed a new time domain full-waveform inversion method for borehole sounding data. The FWI method employ an amplitude envelope-based objective function which captures low-frequency components to provide the initial velocity model for further inversion. Then a global correlation-based objective function is applied for FWI based on the updated initial velocity model. Numerical studies show that modeled anomalies of a single void, multiple voids and fractures are successfully delineated by the inverted Vs velocity profile. The FWI method was applied to field data from a bridge foundation project in a karst area and compared to complementary cross-hole acoustic tomography borehole profiles and drilled corehole data. The single borehole FWI inverted velocity profiles identify voids in agreement with the cross hole tomography and corehole observations. The results demonstrate that FWI is capable of imaging karst voids near drilling boreholes using borehole sonic data.

Experimental Characterization of the Flow Field around Oblong Bridge Piers

The prediction of scour evolution at bridge foundations is of utmost importance for engineering design and infrastructures’ safety. The complexity of the scouring inherent flow field is the result of separation and generation of multiple vortices and further magnified due to the dynamic interaction between the flow and the movable bed throughout the development of a scour hole. In experimental environments, the current approaches for scour characterization rely mainly on measurements of the evolution of movable beds rather than on flow field characterization. This paper investigates the turbulent flow field around oblong bridge pier models in a well-controlled laboratory environment, for understanding the mechanisms of flow responsible for current-induced scour. This study was based on an experimental campaign planned for velocity measurements of the flow around oblong bridge pier models, of different widths, carried out in a large-scale tilting flume. Measurements of stream-wise, cross-wise and vertical velocity distributions, as well as of the Reynolds shear stresses, were performed at both the flat and eroded bed stages of scouring development with a high-resolution acoustic velocimeter. The time-averaged values of velocity and shear stress are larger in the presence of a developed scour hole than in the corresponding flat bed configuration.

Methods to detect and measure scour around bridge foundations

Bridges are indispensable structures vital to the operation of road and rail transportation networks. Crossing rivers and artificial waterways, however, presents a risk to their foundations due to scour actions. Scour is the number one cause for bridge failures and may occur beneath any bridge, large or small, with supports located within the waterway. This paper provides a summary of present scour detection and measurement equipment and associated assessment methodologies. In this regard, particular emphasis is placed on structural health monitoring better to evaluate the presence and influence of potential scour. A Sensitivity Analysis on a newly introduced monitoring system is also assumed. Furthermore, much research has been undertaken to create a technology that can instantly identify and detect bridge scour, improving survey reliability through prior inspection and prompt intervention. This research will explore and evaluate bridge scour detection methods employed and suggest a possible path for developing the detection system to identify scour depth effectively and efficiently. Finally, our key aim is to minimize human effort in identifying and bridge scour by using a quick, easy-to-use, cost-effective process, resulting in fewer injuries and economic savings.

Study on Construction Treatment of Bridge and Culvert Soft Soil Foundation in Highway Bridge Engineering

Study on Construction Treatment of Bridge and Culvert Soft Soil Foundation in Highway Bridge Engineering

Slope stability analysis and protection of deep accumulation excavation foundation pit in the Sichuan Bank of the Kahalo Jinsha River Bridge

The Kahalo Jinsha River Super Large Bridge of the Sichuan Riverside Expressway spans the deep canyon of the Jinsha River and is situated in a high-intensity, complex, and dangerous mountainous area. Long-term deformation and stability of the gravity anchor slope are the main controlling factors affecting bridge safety. The maximum slope height formed by the excavation of the gravity anchor foundation pit on the Sichuan Bank of the Kahalo Jinsha River Bridge is 110m, and the anchorage area is located on the Q3h thick accumulation with a thickness of more than 170 m. First, the important soil mechanical parameters, such as shear strength, deformation modulus and bearing capacity eigenvalues of rock and soil were obtained by conducting field shear tests, deformation tests, and load tests. On this basis, the pseudo-static method was used to simulate the seismic conditions, and a three-dimensional numerical analysis and calculations of the potential instability range of the high slope of the gravity anchor foundation pit excavation were conducted. The results reveal that the slope of the super-deep foundation pit with a huge thick mixed accumulation layer will deform and become unstable under the influence of an earthquake, with a maximum deformation of about 20 m in the slope body. A two-level earthquake prevention and disaster-reduction target for the bridge foundation pit and slope engineering protection is proposed based on the two-level seismic fortification requirements of super-long-span suspension bridges. An active reinforcement scheme of excavation pre-reinforcement, step-by-step excavation, and zoning protection is designed and proposed based on this target and the deformation and stability analysis results of the field test and three-dimensional numerical calculation.

Gravel Mining Activity Impact on Riverbed Erosion and Bridge Foundation Stability

Geomorphological processes pose a risk that deserves attention and planning to avoid that, especially in the section near to east of Tuz bridge. This section of the valley facing a dramatic increase in gravel excavation and sorting of aggregates, consequence led to a change in the pattern of river branches flow from an anabranching river to a single-channel river, which led to a concentration of river discharge during floods. On 9th December 2018, Tuz Bridge was failed due to a heavy rainstorm three days preceding the failure event. The current study aims to conduct a field survey of all the human activities in the study area to assess river changes from remote sensing data the amount of runoff and river peak discharge based on rainfall data using SCS-CN method. In this study, ArcGIS, ArcGIS Earth, Google Earth, and WMS software are incorporated in the data analysis. The revealed results indicate the severe modification of valley morphology and converting the river pattern to flow during flood within a single channel with flow speed exceeded the critical velocity to induce vertical erosion of gravel and sands under the foundations of the bridge and causing the displacement and settlement of the bridge. The study recommends the local administration prevent gravel mining from the river valley at the upstream area of the bridge

Probabilistic Analysis as a Method for Ground Freezing Depth Estimation

Accurate frost depth prediction is an important aspect in different engineering designs such as for pavements, buildings, bridge foundations, and utility lines. This paper presents a probabilistic method of assessment of the depth of soil freezing. Annual (winter) maxima of the position of the zero centigrade temperature measured in the soil were approximated by Gumbel probability distribution. Its parameters were estimated using maximum likelihood method. The results received on the basis of data from 36 meteorological stations in Poland and 50 years of observations, as characteristic values with 50-year return period, reflect the influence of the climatic conditions on the freezing depth. On the other hand, the soil structure and its conditions also play an important role in freezing. Nowadays they may be taken into account using correction coefficients. It is concluded that this method is more precise than a method using the air freezing index because through the use of direct measurements it takes into account additional factors affecting the actual depth of freezing. The obtained results are not the same as those given in the older Polish Standard which was based on the simplified and limited data. The results confirm the impact of climate change on ground freezing depth.

Characterization of bridge substructures explored by leveraging structural identification of a scaled bridge model

Characterization and evaluation of bridge substructures, especially when as-built information is missing, are needed to assess the vulnerability of bridges to natural hazards, other possible causes of bridge failure, and as prerequisites for bridge substructure and foundation reuse. Structural identification has been investigated as a tool for characterizing and evaluating bridge substructures. Structural identification offers advantages over conventional methods especially by integrating information from structural testing and local NDE approaches.During field investigations the authors observed significant challenges to assessing substructure characteristics such as embedded depth, even for simple piers on spread footing foundations. It is found that impact excitation on bridge superstructure or even directly on substructure aiming for conventional flexural modes in the lower frequency band is not sufficient for a reliable identification of the substructure and its surrounding soil.To understand better the challenges limiting reliable structural identification of bridge substructures, a phenomenological scaled bridge model with strip footing, mimicking an actual bridge on shallow foundations, was designed, fabricated and utilized for controlled laboratory testing. The scaled bridge model could be modified to comprehend the sensitivity of bridge substructure modal properties to: i) stiffness of bridge bearings (causing coupling between superstructure and substructure) and ii) foundation substrate compliance. A finite element representation of the physical model, with a Multiphysics Simulation Finite Element Software, was calibrated and was then exploited to perform further sensitivity studies which confirmed the potential of high frequency axial and flexural modes of the substructures to: iii) identify shallow foundation embedded depth, and iv) characterize the soil substructure interaction.Throughout the paper, different challenges affecting structural identification for characterization and evaluation of bridge substructures and possible countermeasures are discussed. Findings of the study indicate that a high frequency bandwidth covering the axial vibrational modes of the substructure is necessary if structural identification is used for estimating shallow foundation embedded depth. Such a bandwidth is not possible in conjunction with ambient monitoring, pointing to the necessity of a controlled multi-inputmultioutput (MIMO) dynamic testing.

Analytical investigation of a new direct Column-to-Cased shaft connection

In regions of high seismicity, the large seismic design forces sustained by the superstructure must be transferred to the bridge foundations. In these situations, in particular in situations with weak soils, cased shafts, which are concrete filled steel tube (CSFT) components, are used for piles and drilled shafts. Prior research shows that these components have large flexural, axial and shear strengths. Typically, the forces are transferred from the column to the pile through a pile cap. However, direct connections are becoming more common, in particular because they have efficiency in terms of placement and can facilitate accelerated bridge construction. This research studies two different connections: (1) direct embedment of the column reinforcement into the pile and (2) an enhanced connection using a ring at the top of the tube in the pile to enhance mechancial bond and reduce embedment depth. The study was conducted using a high-resolution finite element analysis modeling approach validated using large-scale test results of reinforced concrete (RC) and CFST components and connections. The model included advanced constitutive modeling of the concrete as well as modeling of the bond between the steel tube and concrete fill and the reinforcing steel and the concrete fill. The transfer of forces from the yielding reinforcing bars in the RC pier to the concrete fill and tube of the pile is critical for this connection. Different approaches were investigated to achieve transfer without loss of strength or ductility. A supplemental rib inside the tube ultimately was used to enhance the load transfer with the minimum embedment length. The model was used to conduct a parametric study with the following study parameters: the rib location (lR), tube diameter (D), reinforcing bar diameter, and embedment depth (ld). The results were used to propose initial design recommendations.

Fast simulation of railway bridge dynamics accounting for soil–structure interaction

A novel numerical methodology is presented to solve the dynamic response of railway bridges under the passage of running trains, considering soil–structure interaction. It is advantageous compared to alternative approaches because it permits, (i) consideration of complex geometries for the bridge and foundations, (ii) simulation of stratified soils, and, (iii) solving the train-bridge dynamic problem at minimal computational cost. The approach uses sub-structuring to split the problem into two coupled interaction problems: the soil–foundation, and the soil–foundation–bridge systems. In the former, the foundation and surrounding soil are discretized with Finite Elements (FE), and padded with Perfectly Match Layers to avoid boundary reflections. Considering this domain, the equivalent frequency dependent dynamic stiffness and damping characteristics of the soil–foundation system are computed. For the second sub-system, the dynamic response of the structure under railway traffic is computed using a FE model with spring and dashpot elements at the support locations, which have the equivalent properties determined using the first sub-system. This soil–foundation–bridge model is solved using complex modal superposition, considering the equivalent dynamic stiffness and damping of the soil–foundation corresponding to each natural frequency. The proposed approach is then validated using both experimental measurements and an alternative Finite Element–Boundary Element (FE–BE) methodology. A strong match is found and the results discussed.

Evaluation of Weathered Rock Mass Strength and Deformation Using Weathering Indices

Rock weathering and the resulting effects on geotechnical properties of weathered rock mass has long been a concern for geotechnical engineering practicing since the strength and deformational properties of weathered rock masses is needed for analysis and design of underground openings, opens pits and excavations for foundations of dams, bridges and high-rise buildings in and on weathered rock mass. It is a very challenging task to obtain required core samples to determine the strength and deformation behavior for the assessment of weathered rock mass performance. This is because of weathering which causes change in fabric of rock by creating voids and micro cracks after dissolving grain boundaries particularly, at higher stage of weathering. This paper attempt to present a method of sampling and testing of weathered rocks and proposed a weathered rock mass indices chart for estimating rock mass strength and deformation properties. To investigate the applicability of the proposed weathered rock mass indices chart for other regions, available data from literature for same rock has been used along with the extensive testing data generated in the present investigation Deccan plateau basaltic rocks.

ANALYSIS OF METHODS OF RECONSTRUCTION AND RENEWAL OF THE FOUNDATIONS OF HIGHWAY BRIDGES TAKING INTO ACCOUNT THE EXPERIENCE OF MILITARY CONFLICTS

The purpose of the work is to analyze the modern domestic and foreign practice of extending the life of railway and road bridges as part of the problematic state of the transport and road complex, taking into account the impact on the quality condition of these objects of various factors and operating conditions due to their renewal and reconstruction. Methodology. The problematic issues of maintenance and operation of railway and road bridges in modern conditions are highlighted. Comprehensive measures aimed at extending the lifetime of these transport infrastructure objects through major repairs and reconstructions have been identified. On the basis of the analysis, conclusions were drawn about the need to improve the methods of strengthening the foundations of bridges during the renewal and reconstruction. Findings. Generalization of the modern foreign and domestic methods of strengthening the foundations of bridges provided the possibility of researching the most effective, cost-effective and easy-to-perform structures. Four directions of development of foundation strengthening are proposed: 1) increasing the area of support for shallow foundations on natural foundations; 2) arrangement of additional pile foundations with combining them into a common structural system with existing foundations and the construction of additional supports; 3) strengthening the existing pile foundations by changing the bearing capacity of the bases; 4) arrangement of other structural elements to ensure the reinforcement of the existing foundations of bridges. Originality. It consists in setting the task of strengthening the foundations of highway bridges during the renewal or reconstruction. Practical value. Based on the results of the analysis, we can recommend the most economically justified and quickly implemented methods of strengthening the foundations of bridges for design decisions in the implementation of state programs for the construction and development of the transport and road complex of Ukraine and in modern world practice.

Time domain nonlinear kinematic seismic response of composite caisson-piles foundation for bridge in deep water

As a new type of bridge foundation in deep water, the composite caisson-piles foundation (CCPF) is inevitability suffered from multiple hazards such as earthquake, scouring and erosion, especially for sea-crossing bridges in ocean environment. In this study, a simplified method in time domain is proposed for predicting the nonlinear kinematic seismic response of CCPF and the effect of scouring on the seismic response is investigated. The proposed method is verified by the results of centrifuge shaking-table tests. It is found that compared with frequency domain method, the proposed time domain method can give good estimations of the acceleration and the displacement of the CCPF, especially at high frequencies. Moreover, the kinematic seismic response of CCPF designed for the Qiongzhou Strait Bridge is analyzed. The results indicate that the proposed model can effectively simulate the soil nonlinearity, and the soil nonlinearity significantly affects the kinematic seismic response of CCPF, especially the acceleration and displacement time histories. Finally, the scouring effect is considered by an analytical model and the performance of the CCPF under combined earthquake and scouring is investigated.

Low Strain Detection and Numerical Simulation of Pile Integrity

The low strain reflected wave method is used to detect the integrity of pile foundation of a domestic bridge, and various types of defective pile models are constructed. A large number of tests are carried out to analyze the complete pile installation and different defects. At the same time, considering the influence of pile material properties, soil parameters around the pile, boundary conditions and damping coefficient on the reflected wave, the test results are compared with the numerical simulation results. The results show that: low strain detection technology is convenient and easy to operate, but due to its own limitations, it should be combined with numerical simulation and other methods to learn from each other, comprehensive analysis, in order to better judge the integrity of the pile.

A test method for analyzing the deformation of landslide model

In order to study the overall deformation of geotechnical model conveniently, the worksite of landslide bridge foundation reinforced by the front and rear row anti-slide piles in Chenglan railway was taken as an example. On the basis of shaking tabe test of a 1/40 reduced scale model, the landslide deformation caused by vibration waves was monitored through burying self-made phosphor bronze strips in soil. Combined with the horizontal and vertical coordinates of the bending strain points on the phosphor bronze strips, the digital matrix was converted by applying Renka Cline random matrix generation method, and the two-dimensional contour plots were drawn based on it. The results showed that the two-dimensional contour plots reflected the basic law of landslide deformation reasonably, and it revealed the evolution process of landslide deformation and failure. The research conclusions were consistent with the test phenomenon, which met the basic requirements of overall deformation analysis of landslide model. This proposed method can monitor multiple cross sections and was practical for model test.

Effects of Landslides on the Displacement of a Bridge Pile Group Located on a High and Steep Slope

Engineering practice shows that the deformation of the slide-resistant pile may be transferred to the adjacent bridge foundation on an inclined slope, which can compromise the safety of the entire bridge. However, this phenomenon has rarely been considered in the past. To reveal the deformation transfer mechanism between the slide-resistant pile and the adjacent structures, a full-scale field test was performed on a high and steep slope located in a section of a certain railway. A numerical analysis model was constructed to simulate the field test and validate its parameters. Moreover, parametric analysis was also conducted to examine the influence of the pile length, pile diameter, and arrangement of the pile foundation. The results show that the bridge pile foundation is simultaneously affected by the “load transfer effect” caused by the slide-resistant pile and “traction effect” of the sliding slope. With the distance between the pile foundation and the slide-resistant pile increasing, the dominant factor affecting the deformation mode of the pile body is switched from the “load transfer effect” to the “traction effect.” Furthermore, a critical embedment depth exists for the bridge pile foundation built on a high and steep slope, which varies at different locations along the inclined stratum. In addition, using a pile arrangement with a larger pile diameter and lower number of piles is more beneficial for controlling the horizontal displacement of the bridge foundation. The results of the research provide a reference for the safety control of the engineering on the high and steep slope.

Bridge assessment: A case study of Ajaokuta-Itobe Bridge, Kogi State

This report summarizes the assessment carried out as a result of the public uproar on the degree of safety of the Ajaokuta/Itobe Bridge in Kogi state. The public outcry was as a result of a severe damaged expansion joints of the bridge. Visual inspection and concrete strength test were carried out to ascertain the safety condition of Itobe Bridge. Seven out of the total number of eight expansion joint covers were damaged and out of place while all the elastomeric bearings were in good working condition. The scouring of the river bed was not visually pronounced except little at the abutment side of the Abuja-Ayingba approach which is attributed to change of water course. Farming activities within the vicinity of the bridge embankment has no effects on the bridge foundation. The compressive strength test result of some bridge elements selected shows that the values are within the satisfactory range. The assessment recommended the lengthening and desilting of the drainage pipes to prevent further corrosion of the concrete and steel members. The use of sand blasting and repainting of the steel beams was also recommended to protect them from further corrosion. Maintenance of cracks on the reinforced concrete abutment and piers should be carried out. The use of sheet piles filled with compacted sand or gabions around the exposed piles caps to protect the foundation was recommended. Shoreline protection measures should be used in protecting the bridge eroded embankment. Seven out of eight expansion joint devices were damaged therefore exposing the elements of the structure that are otherwise protected by the joint devices. The openings about 47cm-53cm becomes a conduit by which moisture, abrasives, chemicals, and other debris are deposited on the superstructure and substructure below the opening, thereby causing extensive damage. The expansion joints devices should be fixed with proper elastomeric strip seal to protect the bridge from further deterioration.

Characteristics of wave forces on pile group foundations for sea-crossing bridges

The pile group foundation of sea-crossing bridges has various structural forms, and its wave force characteristics are complex. In this study, the Morrison equation and the boundary element method were utilized to establish a calculation model for predicting the maximum wave forces on the pile group foundation with a square pile cap. Moreover, hydrodynamic models of pile group foundations were designed according to the gravity similarity criterion. On this basis, the model test and analytical calculation were carried out to investigate the effect of pile spacings, pile slopes, conical slopes (on the top of the pile cap), and wave parameters on wave forces of pile group foundations. In addition, impact characteristics of waves on the foundation were also analyzed. The results shown that larger pile spacings and pile slopes reduced the wave forces on the foundation, but this relationship weakened with the rise of the water level. The inclined pile could be regarded as a vertical pile for calculating wave forces at high water level. The conical slope increased the water-blocking area on the pile cap, which led to the increase of wave forces on the foundation. When the wave only acted on the pile group, the wave forces on the single pile firstly decreased then increased with the increase of frequencies, and lower wave frequencies (larger periods) induced stronger nonlinear factors of the waves. When the water level was near the bottom of the pile cap, larger wave periods increased the vertical wave forces on the pile cap. The wave impact mainly occurred in the time range from the pile cap first contacting with the wave to the wave crest reaching the middle of the pile group foundation.

Experimental study on local scour at complex bridge piers under steady currents with bed-form migration

Local scour at pile-supported bridge foundations in coastal and offshore areas are an essential factor to engineering design and evaluation. This study experimentally investigates live-bed local scour at complex bridge piers under the influence of bed-form migration. The results show that the variation of the mean scour depth as a function of flow intensity ratio U/Uc (Uc= threshold velocity for incipient motion) depends on the pile-cap elevation and is significantly different to single piers. Instantaneous bed level, cross-correlation analysis, and power spectra show that bed-forms approaching an exposed pile group may be damped, leading to mean bed level fluctuation that are slightly smaller than the bed-form heights. In contrast, when the pile-cap is completely buried by the original bed but can be exposed during scour, approaching bed-forms tend to keep their individual features and cause larger scour fluctuation at pile-cap's leading edge. The enlargement is due to the concurrence between the enhanced (or weakened) scouring capacity and the decreased (or increased) upstream sediment supply. The scour predictor proposed by previous studies is extended to live-bed range and performs better than existing predictors.

Study on the position of load box for pile foundation of Qilu Yellow River Approach Bridge

In theory, the balance point position of O-cell pile test is determined and unique, and the load box should be located at this point. But in practical projects, it is difficult to determine the balance point position accurately. The pile foundation of Qilu Yellow River Approach Bridge bears a large load. In order to reduce the risk caused by the position of load box in O-cell pile test, the double load box technology is adopted in this pile test project. According to the pile design, the soil properties and the loading sequence, the bearing capacity of the pile foundation before and after grouting is estimated. The pile test results show that the project is a successful example for the double load box technology.