Gravity Type Quay Walls Research Articles

THE RESULTS OF THEORETICAL STUDIES FOR DETERMINING OPERATIONAL LOADS ON GRAVITY-TYPE BERTHING STRUCTURES

The current waterfront of Ukrainian ports includes structures that have been developed in the past and have over 50 years of experience. Open-piled quay walls and sheet-pile quay walls are the most common types of quay walls used for berths in Ukrainian ports. However, there are gravity-type quay walls. The share in the total the waterfront is not large. They were built in the past and require modernization and reconstruction. Most of these berthing structures have defects in concrete and reinforcement, which reduce the durability and bearing capacity. Furthermore, the development of freight and passenger maritime traffic and the construction of modern ships led to the need to increase the depths at existing berths and define the operational loads meeting modern requirements. Thus, the issue of reconstruction of gravity-type quay walls is relevant for many ports of Ukraine. The choice of the reconstruction method depends on the correct estimation of the actual technical condition of an existing structure. Gravity-type structures are those that rely primarily on their weight and grip on the foundations to resist any possible adverse load combinations. The requirements for such structures lead to the solution of one of the main tasks ‒ the determination of the reactive capacity of the soil base. The reactive capacity calculation of the soil bases for considered structures is essential. The purpose of the calculation is to provide both strength and stability of soil bases. An improved method for determining the reactive capacity of the soil base of gravity-type quay walls has been developed. This method allows determining the reactive capacity of the soil base in conditions of the mixed stress state (limit and sublimit stress state zones in the soil base are considered). This paper reviews some results of applying the proposed method for the reactive capacity estimation of the soil base of gravity-type quay walls. The obtained results have been used to analyze the preliminary reconstruction options for the mentioned structures and determine operational loads.

On the seismic performance of block type quay walls: Numerical analyses against 1g shaking tank tests

Up to date national and international codes and standards recommends the performance-based design to better estimate the seismic response of the gravity type quay walls. Advances in computer-based solutions paved the way for numerical studies and important developments have been achieved in several commercial computer programs some of which are used for the seismic analysis of gravity type quay walls. Experimental and/or numerical research have been conducted to provide an understanding of the vulnerability of these structures, however, only a few are devoted to the seismic performance of block type quay walls. In this study, a two-dimensional (2D) finite element analysis was performed to simulate the seismic response of three different block type quay walls. A vertical wall and two recently invented hunchbacked walls, namely: first type hunchbacked wall (FHW) with a larger hunch and second type hunchbacked wall (SHW) with a smaller hunch were used in analyses. The calibrated numerical models were used to predict the seismic behaviour of the walls, and the computed horizontal displacements were compared against measured data. In general, the computed response was found to be in satisfactory agreement with the experimental produced one. It was found that the first type hunchbacked wall exhibited the most satisfactory performance compared to the performance of the other studied wall types. The main reason for this is the lower centre of gravity (compared to that of the other walls), resulting in smaller inertia-driven overturning moments at the wall base and therefore smaller rotation-induced horizontal displacements. The worst performance was observed in the vertical wall due to the mobilization of smaller shaft and base shear resistances. The observations were supported by both the numerical and the experimental results.

Experimental study on seismic response of gravity-type quay wall considering input earthquake frequency and excess pore pressure buildup in backfill

In performance-based seismic design of port structures, it is crucial to accurately verify the seismic performance of structures. Therefore, there is an increasing demand for investigation of the seismic behavior of quay walls, considering the comprehensive interaction between the backfill, quay wall, and water. In this study, to evaluate the influence of the earthquake frequency and excess pore pressure buildup in the soil on the seismic responses of a gravity-type quay wall, a dynamic centrifuge test was performed. Four earthquake motions were applied to a quay wall model under saturated soil conditions. The measured records of acceleration responses and pore pressure in the soil and wall displacement showed that the earthquake frequency is strongly associated with permanent displacement of the wall and liquefaction in the soil. Based on time–frequency analysis, the frequency band of the input motion, which mainly contributed to the generation of permanent displacement of the wall, was found. Contrary to the hypotheses of conventional simplified analysis methods, the phase relationship between measured dynamic displacements of the wall and soil, excess pore pressures, and dynamic thrust showed that excess pore pressure buildup in backfill is a crucial factor in determining the dynamic thrust acting on the quay wall.

Inertial behavior of gravity-type quay wall: A case study using dynamic centrifuge test

Quay walls have been extensively investigated since the 1995 Kobe earthquake, with most studies focusing on the revision of design codes and evaluation of seismic active earth pressure. To ensure the quay wall's safety during a strong earthquake, many studies evaluated the interaction between the wall and the backfill soil. Although several studies have reported that the inertial behavior of the quay wall can cause the failure due to its inertia force, the test case describing the dynamic inertial behavior of the quay wall and its failure development has not been introduced enough. In this study, a centrifuge test was introduced to describe failure mechanism of a gravity-type quay wall manifested by its large inertia. The frequency characteristics of the quay wall was discussed using analytical calculations and the transfer functions from the test results. It showed that the analytical calculations well predicted the natural frequencies of the wall under a weak dynamic loading. Under a strong shaking, the natural frequencies of the wall were significantly different from that of the backfill and it implied that the phase difference occurrence between the wall and the backfill due to the wall's inertial behavior. The test results showed that soil liquefaction was induced during the strong dynamic loading only at the backfill soil, followed by vertical settlement of ground due to void redistribution. Consequently, horizontal sliding failure due to the inertial motion of the quay wall was also noted.

Embedded deformation of the rubble-mound foundation of gravity-type quay walls and influence factors

Abstract In this study, the embedded depths of the rocks of the single-layer placement group and the multilayer riprap group were compared through a self-made test device. Besides, a finite element model of a single layer of regular rocks was developed to probe into the factors that impact the embedded deformation of the rubble-mound foundation of a gravity-type quay wall, including the cohesion and angle of internal friction of foundation soil, as well as the particle size of and the interval between rocks. Research results indicated that it was feasible to replace multilayer randomly dumped rocks with single-layer regularly placed rocks. The embedded depth decreased as the cohesion and angle of internal friction of soil increased. The influence of load on the embedded depth was small when the cohesion was less than 10 kPa or the angle of internal friction was smaller than 40°. When the load was lower than 80 kPa, the impact of the particle size of rocks on the embedded depth would be negligible, and such impact grew along with the load. When the load was below 100 kPa, the interval between rocks exerted relatively minor influence on the embedded depth: under a constant porosity, the embedded depth would decrease as the interval increased, and this correlation became more significant when the load exceeded 800 kPa; under varied porosities, a larger interval would lead to an increased embedded depth but the increase would be limited within a range of 10% of the original depth.

Improved performance-based seismic coefficient for gravity-type quay walls based on centrifuge test results

Verifying the seismic performance of port structures when the force balance limit is exceeded is important for the performance-based seismic design of gravity-type quay walls. Over the last three decades, performance verification methods have been developed that consider the effects of the design earthquake motion, geotechnical conditions, and structural details on the deformation of a quay wall to accurately predict earthquake-induced damage. In this study, representative performance verification methods (i.e., simplified dynamic analysis methods extending from the Newmark sliding block method and performance-based seismic coefficients developed in Japan) were quantitatively assessed with actual cases of earthquake-damaged quay walls and the results of dynamic centrifuge tests previously conducted under various conditions (i.e., different wall heights, earthquake motions and the thickness of subsoil). The dynamic centrifuge test results suggested directions for improving the performance-based seismic coefficients of the representative methods, while their field applicability and reliability were confirmed according to the actual earthquake records.

Lateral spreading of ports in the 2014 Cephalonia, Greece, earthquakes

A case history is presented of lateral spreading in two reclaimed port areas of the Cephalonia island, Greece, in the 2014 earthquake doublet (Mw 6.1 & 6). Lateral ground displacements along 24 transects perpendicular to the quay walls in the two port areas were directly measured by ground surveys. Liquefaction of gravel-size fills was observed throughout the ports and was more pronounced in Lixouri port where ground motions were higher. The maximum cumulative horizontal ground displacements ranged from 3 cm to 152 cm, depending on the transect location and height of free face, whereas the inland extent of lateral ground movement ranged from 10 m to 90 m. Lateral movement of the quay walls in Argostoli Port was lower compared to Lixouri Port. Strong motion recordings in the two port areas as well as pertinent seismotectonic data are also presented along with the available geotechnical data compiled by integrating information from exploratory borings, trial pits, site geology and eye-witness accounts of the reclamation history of the areas. Average cumulative lateral displacements for groups of transects, characterized by similar height of quay wall and field conditions were derived and compared to lateral spreading predictions using an empirical relationship for free field conditions. It was found that the magnitude of lateral spreading behind the gravity-type quay walls was significantly lower compared to empirical predictions based on the assumption of free field conditions. The reduction of lateral ground movement depends on the height of quay wall and may even be an order of magnitude lower for wall heights of 6 m or greater. The findings of this study contribute in assessing quay wall movement in port areas especially when liquefaction has occurred behind the wall.

A basic study on the application of LRFD in “the technical standard for port and harbour facilities in Japan”: a case of gravity type quay wall in a persistent design situation

ABSTRACTThe Partial Factor Method (PFM) based on the Level 1 reliability design method was introduced in 2007 to the Technical Standards for Port and Harbour Facilities (TSPHF-2007) in Japan. After nearly 10 years of practical use of TSPHF-2007, the design standard has been revised based on requests from the practitioners who recommend the transition from the PFM to the Load Resistance Factor Design (LRFD). In this paper, we discuss the setting method of the target failure probability to determine the partial factors based on code calibration. Furthermore, we examine the impacts of implementing the LRFD concept to the TSPHF by taking the sliding and overturning of a gravity type quay wall as an example to represent port and harbour facilities. We found no practical difference in caisson width derived using the LRFD and the PFM, whereas the degree of matching of the target failure probability was somewhat more precise for the PFM. This finding indicates that the LRFD is a more reasonable design method than the PFM in terms of the simplicity of the performance function itself and the ease of engineering interpretation during the design procedure.

Evaluation of performance-based seismic coefficient for gravity-type quay wall via centrifuge tests

Conventional simplified analysis methods for seismic design of gravity-type quay wall are based on providing capacity to resist a design seismic force, but they do not provide information on the performance of a structure when the limit of the force-balance is exceeded. In order to overcome the limitation of conventional seismic design methods, a performance-based seismic coefficient (khk) concept which can verify the performance of port structures exceeding the limit of force-balance was proposed in the technical standards and commentaries for port and harbour facilities in Japan, published in 2007. The khk concept considers the deformation of the quay wall, the wall height, the effect of frequency characteristics and duration of the ground motions, and the natural period of the ground. This paper proposes a performance verification method for the gravity-type quay wall during earthquakes through dynamic centrifuge model tests. The centrifuge tests were used in the present study to validate the proposed khk concept for evaluating the seismic performance of the quay wall under various conditions. The reliability of the khk concept was evaluated for different wall heights, earthquake motions and the thickness of subsoil, which are the primary variables in the khk equation. In addition, some improvements that should be considered in the future revision of the khk equation are discussed in this research.

A Discussion on the Seismic Coefficient for Gravity Quay Wall Considering Frequency Characteristics of Input Earthquake

Pseudo-static approach has been conventionally applied for the design of gravity type quay walls. In this method, seismic coefficient (kh), expressed in terms of acceleration due to gravity, is used to convert the real dynamic behavior to an equivalent pseudo-static inertial force for seismic analysis and design. Therefore, the calculation of an appropriate kh considering frequency characteristics of input earthquake is critical for representing the real dynamic behavior. However, the definitions of kh, which is used for simplified analysis in Korea, focuses only on convenience that is easy to use, and the frequency characteristics of input earthquake are not reflected in the kh definitions. This paper evaluates the influences of the frequency characteristics of input earthquake on kh by initially reviewing the kh definitions in the existing codes of Japan for port structures and then by performing a series of dynamic centrifuge tests on caisson gravity quay walls of different earthquake input motions (Ofunato, Hachinohe). A review of the existing codes and guidelines has shown that the kh values are differently estimated according to the frequency characteristics of input earthquake. On the other hand, based on the centrifuge tests, it was found that the permanent displacements of wall are more induced when long-period-dominant earthquake is applied.

Seismic Displacement Evaluation Chart Method for Caisson Quay Walls Improved by the Vibro-Compaction Method

Gravity type caisson walls are a type of popular but easily damaged waterfront construction structure, especially in seismic regions. Various forms of mitigation measures have been successfully and economically applied to improve their performances under the influence of soil liquefaction. Establishment of an effective, reliable, and easily-implemented liquefaction remedial design process based on a commonly used ground improvement technology is important for routine practice. To solve this problem, the vibro-compaction method, as one the most widely used accepted liquefaction remediation method, is applied as the countermeasure to improve a gravity type quay wall damaged by seismic-liquefaction in this study. More than three hundred cases of numerical analyses with variations of the improved zone configurations, improved soil properties and levels of seismic excitation loading were conducted. Based on the results of the parametric study, numerous correlations among various improved zone configurations, improved relative densities of the soils, excitation level, and improved performances of the caisson-wall structure are established. Therefore, a simple chart design procedure based on the established correlations is proposed to estimate the improved residual displacement of gravity caisson quay walls remediated by the vibro-compaction method. The results can be used as a convenient reference for liquefaction mitigation of gravity caisson wall using vibro-compaction method in routine practice.

Seismic response of hunchbacked block type gravity quay walls

Earthquakes near major cities may cause big social and economic impacts. Damages to port facilities may cripple the economy. The past twenty years’ experience has proven the high vulnerability of the port facilities. This fact, along with the economic importance of port structures, indicates the need for better seismic design approaches for berth structures and cargo handling facilities. In the recent decades, there have been many incidences of failure of gravity type quay walls. These failures have stimulated research interest in the development of performance-based design methods. In this paper, two different hunchbacked block type quay walls with different back face shape were studied. A series of 1-g shaking tank tests was performed using a 1/10 scaled block type quay wall with gravel backfill materials on firm non-liquefiable sea bed conditions subjected to different harmonic loads. The shaking tank tests provided insight into the wall displacements and the total dynamic pressures by analyzing pressure components at the contact surface between the saturated gravel backfill soil and the wall. It is concluded that the back-face shape of the walls is an important factor and the larger positive slope of the wall improves the overall seismic stability.

Probabilistic Assessment of Pseudo-Static Design of Gravity-Type Quay Walls

Failure of the quay walls due to earthquakes results in severe economic loss. Because of hazards threatening such inexpensive nodes of national and international transportation networks, seismic design of quay walls is still an evolving topic in marine structural engineering. This study investigates the sensitivity of the gravity-type quay wall stability respect to uncertain soil and seismic properties using ultimate limit-sate pseudo-static design process. Stability is defined in terms of safety factor against sliding (sfs), overturning (sfo) and exceeding bearing capacity (sfb). In order to assess the forces exerting on quay walls, to be more accurate, pore water pressure ratio, horizontal and vertical inertia forces, fluctuating and non-fluctuating components of hydraulic and soil pressure were considered. It was found that the increase of water depth in front of the quay, vertical and horizontal seismic coefficients, and pore water pressure ratio play important roles in reduction of all mentioned safety factors. Increase of specific weight of the rubble mound, backfill and foundation soil, friction angle of wall-foundation/seabed interface and wall back-face/backfill interface and friction angle of backfill soil, lead safety factors to magnify. A comprehensive sensitivity analysis was also performed using the tornado diagrams. Results of this study could give designers insights into the importance of uncertain soil and seismic factors, in order to choose geometry of the design in a way that its analysis and assessment is less relied on severely uncertain parameters and to introduce more reliable and economic quay walls.

A coupled soil-fluid-structure simulation of the near-field earthquake effects on gravity type quay-walls

This study focuses on non-linear seismic response of concrete gravity quay-wall structures subjected to near-fault ground motions, a subject which seems not to have received much attention in the literature. A two-dimensional coupled fluid-structure-soil finite element modelling is employed to obtain the quay-wall response. The seawater medium is represented by acoustic type, potential based fluid elements. The elasto-plastic behavior of the soil medium is idealized using Drucker-Prager yield criterion based on associated flow rule assumption. Four nodded plane strain elements are used to model the concrete wall, foundation, subsoil, backfill and seabed zones. Fluid Structure Interface (FSI) elements are considered between the seawater interfaces with the quay-wall and the seabed. Frictional contact elements are employed between the wall and soil interfaces. The numerical model is validated using field measurements available for permanent drifts in a quay-wall damaged during Kobe earthquake. Reasonable agreements are obtained between the model predictions and the field measurements. Non-linear seismic analyses of the selected quay-wall subjected to both near-fault and far-fault ground motions are performed. An incremental dynamic analysis approach (IDA) is used. In general, at least for models examined in the current study, the gravity quay-walls are found to be more vulnerable to near-field, in comparison with the corresponding far-field, earthquakes.

Pile group response to liquefaction-induced lateral spreading: E-Defense large shake table test

This paper presents the results of a large-scale shake table test at E-Defense facility on a pile group located adjacent to a gravity-type quay wall and were subjected to liquefaction-induced large ground displacements. Extensive liquefaction-induced large ground lateral spreading displaced the quay wall about 2.2m and damaged the pile foundation. The pile foundation consisted of a six-pile group which supported a footing and a superstructure model. Large lateral soil displacements were measured by several sensors such as inclinometers and the results favorably agreed with the directly observed deformations. Soil lateral displacement decreased as the distance from the quay wall increased landward. The piles were densely instrumented and the measured bending strain records were able to explain the damage to the piles. Lateral pressures of the liquefied soil exerted on the piles were measured using earth pressure (EP) sensors. The application of two design guidelines (JRA [1] and JSWA [2]) for estimation of liquefaction-induced lateral pressure on piles is discussed and their advantages and shortcomings are addressed. Furthermore, two simplified methods (Shamoto et al. [3] and Valsamis et al. [4]) are employed to predict the extent of liquefaction-induced large ground displacements and they are compared to the measured deformations. Finally, their accuracy for predicting the liquefaction-induced lateral displacements is evaluated and practical recommendations are made.

Dynamic Soil-Structure Interaction of a Gravity Quay Wall and the Effect of Densification in Liquefiable Sites

AbstractThe lateral spreading of backfill soil caused by displacement of gravity-type quay walls is a major concern for geotechnical engineers. This paper evaluates the efficiency of a technique for mitigation of damage to quay walls, which involves densification of loose sand around the toe. The beneficial and unfavorable effects of densification of sand of different locations of the gravity-type quay walls are also answered. For these purposes, numerical simulations (using a finite-element code) and shake table tests were conducted. From numerical simulations and model tests, it was observed that the displacement of a gravity-type quay wall occurred mainly because of shear strain in the foundation. It was also found that the densification of soil at the toe could mitigate the quay wall damage significantly.

Observations of dynamic and non-dynamic interactions between a quay wall and partially stabilised backfill

The dynamic and non-dynamic interactions between a gravity-type quay wall and a backfill ground were investigated by centrifuge model testing, considering cases in which a rigidly cement-stabilised ground existed at varying distances from the quay wall. In conducting the centrifuge tests, the performance of the instrumentation applied to measure the pressure from granular soils was critically assessed. At non-dynamic states, the backfill confined between the quay wall and the rigidly stabilised soil block exerted smaller earth pressure at deeper locations, at both apparently active and transient states. The calculation, based on perfect plasticity and considering friction arching, was useful in explaining these results. A similar feature was also observed during the steady-state oscillations, in the case of dry sand backfill, and was associated with the system’s increased seismic stability. In underwater cases, the pore water fluctuations in the backfill dominated the total earth pressure behaviour, with the active pressure being smaller again from a confined fill than from a fully extending one. Despite the reduced active pressure, placing the stabilised soil in the proximity of the quay wall increased the wall’s permanent seaward movement, unless the two bodies were in direct contact. This ostensible association of smaller active pressure with greater instability in the underwater cases cannot be explained by the conventional, simplified conception of the active earth pressure as a unilateral cause of instability. The evaluation of such unconventional backfill conditions seems to require rigorous consideration of the simultaneous soil–water-structure interactions.

응답면 기법을 이용한 잔교식 안벽의 신뢰성 해석

응답면 기법을 사용하여 잔교식 안벽의 신뢰성 해석을 수행하였다. 잔교식 안벽은 중력식 안벽과 달리 상부가 강관파일에 의해 지지되는 유연구조물로 한계상태함수가 음함수로 존재한다. 따라서, 한계상태함수를 양함수로 근사하기 위해 응답면 기법을 사용하였다. 응답면 기법을 이용한 LevelII신뢰성해석 방법을 통해 지진하중에 의한 잔교식 안벽의 신뢰도지수를 계산하고, 중요도 추출법을 통해 검증하였다. 수치해석으로는 직항식, 사항식을 각각 해석하였다. Reliability analysis of pile type quaywalls were done by using response surface method. Pier structures have implicit form of limit state function since they are flexible in motion, which is different from gravity type quaywalls. To solve a reliability analysis problem with implicit limit state function, response surface method was applied. Reliability indices of structure under seismic load were found for pier structures Then, they were compared with those found by simulation method. In numerical analysis, both the inclined type and vertical type were analyzed.

Seismic behaviour of gravity-type quay wall backfilled with granular treated soil

含水比が高い軟弱な粘土・シルト系の土を改良して比較的高強度な粒状体（造粒固化土）を作製する技術がある。一般的な地盤材料に比べて造粒固化土は軽量であり，例えば重力式ケーソン岸壁背後の埋立材に適用すれば，地震時におけるケーソンの水平変位量を低減できる。本研究では，岸壁の振動特性を詳細に調べ変位低減のメカニズムを明らかにすることを目的として，動的変形特性試験および動的遠心模型実験を実施した。模型実験では，ケーソンへ作用する土圧を計測し，その土圧と振動特性の関係を調べた。その結果，造粒固化土で形成された地盤からケーソンへ作用する地震時土圧は小さく，これを主要因として変位量が低減されることを確認した。

Model tests on behaviour of gravity-type quay walls subjected to strong shaking

Seismic stability of gravity-type quay walls and prevention of their large distortion are of major concern from a disaster prevention view point as well as in the sense of successful restoration after strong seismic events. There are, however, many existing walls which are of limited seismic resistance and would not be safe under increasing magnitude of design earthquakes. The present study conducted shaking model tests in both 1-g and 50-g centrifugal fields in order to demonstrate the efficiency of available mitigation technologies. Test results suggest that soil improvement in the loose foundation sand can reduce the quay wall damage to a certain extent when the intensity of shaking is around 0.30g. In contrast, under stronger shaking, the centrifugal tests manifested that those measures are not promising because of the increased effects of seismic inertia force.