Seabed Soil Research Articles

Response spectrum method for seismic analysis of monopile offshore wind turbine

Monopile offshore wind turbines (MOWT) are inserted into sea water and sea bed soil. As the piles are usually embedded into the soil as deep as about 40 m, dynamic pile-water and pile-soil interactions, as well as seismic excitation non-uniformity, often occur under earthquake. In this paper, the response spectrum method (RSM) is developed to calculate the maximum response of MOWT considering the pile-water and pile-soil interactions subjected to the non-uniform seismic excitation. The tower and pile are modeled by Timoshenko beam elements, with both nacelle and rotor including hub and blades integrated as a lumped mass at the top of the tower. The pile-water and pile-soil interactions are considered by added mass and soil spring at their interfaces, respectively. The non-uniform seismic excitation is obtained by the site transfer function from the horizontal earthquake motions or design response spectrum at the water-soil interface. The seismic analysis model is solved by using a multiple-support RSM under design response spectrum. Seismic responses of a case of 5-MW MOWT on two types of soil sites are analyzed. The results indicate that the pile-water and pile-soil interactions and seismic excitation non-uniformity should be considered in analyzing such seismic problems of MOWT, while the RSM can be an effective tool.

A multi-spring model for monopile analysis in soft clays

The offshore wind industry in China has seen a rapid development in recent years and is projected to account for half of global yearly installed capacity in the years to come. Monopiles are a popular foundation solution for supporting offshore wind turbines. However, due to challenging seabed soil conditions, which often feature thick normally consolidated soft clays and harsh environmental loading (i.e. frequent occurrence of typhoons), extremely long monopiles are often designed. The large monopiles are costly to fabricate and install and sometimes kills the viability of the concept in cases where the bedrock is relatively shallow and expensive piling in rock is otherwise required. However, the state-of-practice for designing these monopiles in clays is typically by using the API p-y springs, which are widely known to underestimate soil-pile interaction stiffness and capacity for large diameter monopiles. Improvement to the design method can therefore have significant economic implications to the industry. The paper presents an effort toward this direction. A multi-spring beam-column model suitable for monopile design in soil conditions in China is proposed. The model features three soil spring components, namely the lateral p-y spring, the pile tip base shear s-y spring and rotational m-θ springs along the pile shaft. The validity of the model is verified by a comprehensive suite finite element parametric analyses. Guidance for incorporating the cyclic loading effect into design is also provided. The model proposed in this paper has large potentials for application in design practice.

The post-installation consolidation settlement of jack-up spudcan foundations in clayey seabed soils

The post-installation consolidation settlement of spudcan foundations is an issue of concern for the offshore jack-up industry, especially when jack-up rigs operate for long periods. Although there are field records of excessive spudcan settlement during the rig operation, there are no guidelines available for operators to assess and project the consolidation settlement development. This paper reports a study dedicated to this specific subject. The spudcan installation and consolidation under operational load were continually modelled using an effective-stress large deformation finite element technique. The feasibility and reliability of the numerical calculation were first verified by comparison with centrifuge experiments. Parametric studies were then undertaken for spudcans under various soil, loading, embedment and geometrical conditions, so as to identify appropriate forms of dimensionless settlement and time which can unify the settlement time histories of different scenarios. Particular attention was paid to the development of the dimensionless time, which can reflect the drainage effect of the seabed and hence the influence of embedment depth. The unified settlement development curve may be helpful for operators to assess the consolidation degree, project the final settlement and even back-calculate the operative coefficient of consolidation.

Dynamic response analysis of submarine tunnel under different wave loads

Based on theory of Biot’s dynamic consolidation and the elastic dynamics, this paper considers seabed soil and the contact effect of the tunnel, the seabed soil along the depth direction variability and viscoelastic boundary. The two-dimensional finite element model is established to compare the wave force acting on the seabed surface, which causes the internal stress of the tunnel and its dynamic response of the seabed in the first-order elliptic linear wave, cosine wave and the second order stokes wave. Results show that when the relative water depth is larger, the first-order elliptical cosine wave theory used to calculate the dynamic response of the seabed-tunnel will underestimate the seabed soil liquefaction resistance and tunnel resistance to deformation ability. And when the relative water depth is smaller, the linear wave theory to solve the dynamic response of the seabed-tunnel will overestimate the seabed soil liquefaction resistance and the ability to resist deformation of the tunnel. With the increase of L/d and T wave parameter, the first-order elliptical cosine wave and the degree of nonlinear second order stokes wave are in increase. Compared with the linear wave, the seabed soil around the tunnel of pore water pressure, displacement and the internal stress amplitude of the tunnel are obviously increasing.

Seismic Dynamics of Pipeline Buried in Dense Seabed Foundation

Submarine pipeline is a type of important infrastructure in petroleum industry used for transporting crude oil or natural gas. However, submarine pipelines constructed in high seismic intensity zones are vulnerable of attacks from seismic waves. It is important and meaningful in engineering design to comprehensively understand the seismic wave-induced dynamics characteristics of submarine pipelines. In this study, taking the coupled numerical model FSSI-CAS 2D as the tool, the seismic dynamics of a submarine steel pipeline buried in dense soil is investigated. Computational results indicate that submarine pipeline buried in dense seabed soil strongly responds to seismic wave. The peak acceleration could be double of that of input seismic wave. There is no residual pore pressure in the dense seabed. Significant resonance of the pipeline is observed in horizontal direction. Comparative study shows that the lateral boundary condition which can avoid wave reflection on it, such as laminar boundary and absorbing boundary should be used for seabed foundation domain in computation. Finally, it is proven that the coupled numerical model FSSI-CAS 2D is applicable to evaluate the seismic dynamics of submarine pipeline.

Theoretical Analysis of Bearing Capacity of Shallowly Embeded Rectangular Footing of Marine Structures

In this paper, the finite element analysis software ABAQUS is used to analyze the ultimate bearing capacity of three-dimensional rectangular footing of marine structures. The deformation law and the failure mode of homogeneous seabed soil beneath the rectangular footing are analyzed in detail. According to the equivalent plastic strain of soil under rectangular footing, an allowable velocity field of homogeneous seabed soil is reasonably constructed. Based on the plastic limit analysis theory of soil mass and by using the Mohr-Coulomb yield criterion, an upper bound solution of the ultimate bearing capacity of three- dimensional rectangular footing on general homogeneous seabed soil is derived, and a correction factor of ultimate bearing capacity of three-dimensional rectangular footing is given. To verify the rationality and applicability of this theoretical solution, some numerical solutions are achieved using the general-purpose FEM analysis package ABAQUS, and comparisons are made among the derived upper bound solution, the solution of Vesic, and the solution of Salgado et al. The results indicate that the upper bound solution of the three-dimensional shallowly embedded rectangular footing proposed in this paper is accurate in calculating the bearing capacity of homogeneous seabed soil. For undrained saturated clay foundation and sandy foundation with smaller internal friction angle, this upper bound solution can evaluate the ultimate bearing capacity of rectangular footing; with the gradual increase of the internal friction angle of the soil, the ultimate bearing capacity of the proposed upper bound solution is slightly higher than that of the rectangular footing.

DYNAMIC RESIDUAL SEABED RESPONSE AROUND A MOVABLE PILE FOUNDATION

Wave-induced seabed soil response and its resultant liquefaction is common observed in a silt seabed with relative poor drainage condition, which poses a great threaten to the foundation safety of marine structures. Regarding the governing equations, three different approaches namely the Fully-dynamic (FD), Partialdynamic (PD) and Quasi-static (QS) model, have been used in the previous studies. Among these, both PD and FD approaches consider the effect of the inertial terms of soil skeleton/fluid. It has been reported in the literature that effects of the inertial terms on the seabed response could not be neglected, especially for the seabed around a movable structure (Ulker et al., 2010). However, these studies only focused on the oscillatory mechanism which are probably seen in a sandy seabed with high permeability. Recently, Zhao et al. (2017) investigated the residual soil response around a pile foundation by integrating a RANS wave model and a QS seabed model. In their study, the inertial terms of soil skeleton and pore water were neglected. To the authors’ best knowledge, up to now, effects of the inertial terms on the residual response of a silt seabed have not been investigated.

The influence of nonlinear hysteretic seabed interaction on slug-induced stress oscillations in steel catenary risers

Steel catenary risers (SCRs) are usually cost-effective solutions in the development of offshore fields and the transferring of the hydrocarbons from the seabed to the floating facilities. These elements are subjected to the fatigue loads particularly in the touchdown zone (TDZ), where the oscillating SCR is exposed to cyclic contact with the seabed. The slug-induced oscillation is a significant contributor to the fatigue loads in the TDZ. The cyclic seabed soil softening under the wave-induced riser oscillations and the gradual penetration of the SCR into the seabed are widely accepted to have a significant influence on SCR fatigue performance. However, this has never been investigated for slug-induced oscillations due to the lack of integrated access to comprehensive numerical models enabling the simulation of the riser slugging and nonlinear hysteretic riser-seabed interaction at the same time. In this paper, an advanced interface was developed and verified using the multi-point moving tie constraint in order to examine the influence of cyclic seabed soil softening on slug-induced oscillations of SCR. The interface was integrated with a pre-developed user subroutine for modeling of the nonlinear hysteretic riser-seabed interaction and incorporated into a global SCR model in ABAQUS. A comprehensive parametric study was conducted to investigate the influence of slug characteristics and nonlinear seabed soil model on slug-induced, wave-induced, and combined wave/slug induced oscillations of SCR in the TDZ. It was observed that the nonlinear seabed model could significantly affect the embedment of the SCR into the seabed under the slug-induced oscillations and consequently improve the fatigue life. The developed user interface was found to be a strong framework for modeling riser slugging.

Stability analysis of a composite breakwater at Yantai port, China: An application of FSSI-CAS-2D

In offshore areas, quaternary loose seabed soils widely distribute around the world, and a great number of offshore structures actually have been constructed on quaternary seabed floors. In practical engineering, it is highly necessary to evaluate the stability of offshore structures built on quaternary seabed floors under the impact of extreme ocean waves. Based on the VARANS equation and the dynamic Biot's equation, an integrated numerical model FSSI-CAS 2D has been developed by Ye et al. (2013b) to investigate the interaction between ocean waves, marine structures and their seabed foundations. In this study, taking the composite breakwater project in the west harbour zone of Yantai port in China as an engineering case, the integrated numerical model FSSI-CAS-2D is used to evaluate the stability of the composite breakwater under the impact of fortified ocean waves with a 50 years recurrence period. Computational results indicate that the composite breakwater at west harbour zone of Yantai port would be generally stable during its service life. This application demonstrates that the integrated model FSSI-CAS-2D is applicable, and suitable for practical engineering. The case study illustrated in this study can provide ocean engineers with an excellent case demonstration of engineering application, to evaluate the stability of offshore structures under the impact of extreme ocean waves.

Analytical investigation of disturbance of seabed-sampled soil specimens and its influence on unconfined strength

In view of the need to utilize ocean space and to develop seabed resources, the assessment of the stability of deep seabed soil has emerged as an important challenge in the field of geomechanics. To study seabed stability, the strength and stiffness of the natural ground must be ascertained. Accordingly, it is necessary either to conduct laboratory testing on soil specimens sampled from the seabed or to estimate the strength and stiffness by in-situ tests. While in the future it may be reasonable to conduct in-situ tests to estimate the stiffness and strength of seabed soil, it will still be necessary to compare the physical properties measured by in-situ testing with those measured by laboratory testing in advance of these determinations. In short, soil specimens must be sampled from the actual deep seabed, and laboratory mechanical tests must be conducted on the sampled soil specimens. However, soil sampled from the ocean bottom is subject to effects that differ from those exerted on soil sampled from the earth. More specifically, the non-negligible effects of disturbance are expected with soil sampled from the ocean bottom. The effects of disturbance occur during the sampling process due to the vaporization of dissolved gases, as these soil specimens are under relatively higher pressure and contain pore water with a high amount of dissolved gases. Therefore, numerical simulations were conducted in the present study to investigate the effects of vaporized dissolved gases on the mechanical behavior of soil specimens during sampling and on the undrained shear strength as determined by laboratory tests. The analyses revealed that the combination of the decreasing effective stress caused by the sampling and factors such as overconsolidation and unsaturation is attributable to the difference between the soil strength ascertained by laboratory testing and the in-situ soil strength.

Numerical analysis of wave-induced poro-elastic seabed response around a hexagonal gravity-based offshore foundation

In order to prevent the future risk of soil and structural failures for the offshore foundations, it is essential to evaluate the seabed soil behaviors in the vicinity of the foundation under dynamic wave loadings. The objective of this paper is to investigate the wave-induced soil response and liquefaction risk around a hexagonal gravity-based offshore foundation. Three-dimensional (3D) numerical analysis is performed by applying an integrated multiphysics model developed in the finite volume method (FVM) based OpenFOAM framework. The integrated model incorporates solvers of the nonlinear waves, the linear elastic structure and the anisotropic poro-elastic seabed soil. The free surface model and soil model are verified by grid convergence studies. The wave-induced soil response model is validated by reproducing a laboratory experiment and a good agreement is obtained.Distributions of wave-induced shear stress, pore pressure, vertical displacement and seepage flow structure in the seabed are investigated. It is found that the presence of the foundation significantly amplifies the wave-induced shearing effect and vertical displacement in the underlying seabed soil. Seabed consolidation state in the presence of the structure is evaluated. Since the foundation is embedded in the seabed at a depth, the vertices of the hexagonal foundation cause the stress concentration in the nearby soil during the consolidation process. Therefore, the momentary liquefaction at the vertices is not as significant as that at the edges due to the high initial effective stress. A parametric study with different wave heights is conducted to examine the changes of soil response and momentary liquefaction depth around the hexagonal foundation. Effects of isotropic and anisotropic soil permeability on the pore pressure distribution are investigated. It shows that the effect of anisotropic permeability should be considered for the medium sand that is modelled in the present study.

Comparison of Soil Models in the Thermodynamic Analysis of a Submarine Pipeline Buried in Seabed Sediments

Abstract This paper deals with mathematical modelling of a seabed layer in the thermodynamic analysis of a submarine pipeline buried in seabed sediments. The existing seabed soil models: a “soil ring” and a semi-infinite soil layer are discussed in a comparative analysis of the shape factor of a surrounding soil layer. The meaning of differences in the heat transfer coefficient of a soil layer is illustrated based on a computational example of the longitudinal temperaturę profile of a -kilometer long crude oil pipeline buried in seabed sediments.

Wave & current-induced progressive liquefaction in loosely deposited seabed

Quaternary newly deposited loose seabed soil widely distributes in offshore area in the world. Wave-induced residual liquefaction in loose seabed floor brings great risk to the stability of offshore structures in extreme climate. Understanding of the characteristics of wave-induced residual liquefaction in loose seabed is meaningful for engineers involved in design of offshore structures. In this study, wave & current-induced residual liquefaction in loose seabed floor is investigated deeply and comprehensively adopting a validated integrated numerical model. The time history of wave & current-induced pore pressure, effective stress, shear stress, lateral pressure coefficient K0, stress angle, displacement of seabed soil are all quantitatively demonstrated. The variation process of progressive liquefaction, stress path, as well as stress-strain relation also are illustrated in detail. The classic effective stress principle has been modified to describe the nonlinear phenomenon that the reduction rate of vertical effective stress σ′z is faster than that of horizontal effective stress σ′x and σ′y accompanying residual pore pressure build up. It is shown that the integrated numerical model FSSI-CAS 2D incorporating PZIII soil model can effectively and precisely capture a series of nonlinear dynamic response characteristics of loose seabed floor under wave & current loading. The computational results further confirm the wave & current-induced liquefaction in loose seabed soil is progressively downward, initiating at seabed surface. Besides, it is found that three physical processes, including vertical distribution of oscillatory pore pressure, time history of stress angle as well as lateral pressure coefficient K0 could be taken as indirect indicator to judge the occurrence of wave-induced residual liquefaction, and predict the residual liquefaction depth in loose seabed. It is also found that the progressive liquefaction process is significantly affected by wave height, permeability and saturation of seabed soil.

Nonlinear standing wave-induced liquefaction in loosely deposited seabed

Wave-induced residual liquefaction in loose seabed floor brings great risk to the stability of offshore structures in extreme climates. Understanding the characteristics of wave-induced residual liquefaction due to pore pressure buildup in loose seabed is meaningful for engineers involved in the design of offshore structures. In this study, standing wave-induced residual liquefaction is investigated deeply and comprehensively adopting a validated integrated numerical model. The time history of standing wave-induced pore pressure, effective stress, shear stress, lateral pressure coefficient $$K_0,$$ stress angle, and displacement of seabed surface are all quantitatively demonstrated. The variation process of progressive liquefaction, stress path, as well as the stress-strain relation also are illustrated in detail. It is shown that the integrated numerical model FSSI–CAS 2D (FSSI: fluid–structures–seabed interaction, CAS: Chinese Academy of Sciences) incorporating the PZIII soil model can effectively and precisely capture a series of nonlinear dynamic response characteristics of loose seabed floors under standing wave loading. The computational results further confirm that the wave-induced liquefaction in loose seabed soil is progressive downward, initiating at the seabed surface. In addition, it is found that two physical processes, including vertical distribution of oscillatory pore pressure and time history of stress angle possibly could be used to judge the occurrence of wave-induced residual liquefaction in loose seabeds. Furthermore, it is also found that the progressive liquefaction process is significantly affected by wave height, permeability and saturation of seabed soil.

Subsidence estimation of breakwater built on loosely deposited sandy seabed foundation: Elastic model or elasto-plastic model

In offshore area, newly deposited Quaternary loose seabed soils are widely distributed. There are a great number of offshore structures has been built on them in the past, or will be built on them in the future due to the fact that there would be no very dense seabed soil foundation could be chosen at planed sites sometimes. However, loosely deposited seabed foundation would bring great risk to the service ability of offshore structures after construction. Currently, the understanding on wave-induced liquefaction mechanism in loose seabed foundation has been greatly improved; however, the recognition on the consolidation characteristics and settlement estimation of loose seabed foundation under offshore structures is still limited. In this study, taking a semi-coupled numerical model FSSI-CAS 2D as the tool, the consolidation and settlement of loosely deposited sandy seabed foundation under an offshore breakwater is investigated. The advanced soil constitutive model Pastor-Zienkiewics Mark III (PZIII) is used to describe the quasi-static behavior of loose sandy seabed soil. The computational results show that PZIII model is capable of being used for settlement estimation problem of loosely deposited sandy seabed foundation. For loose sandy seabed foundation, elastic deformation is the dominant component in consolidation process. It is suggested that general elastic model is acceptable for subsidence estimation of offshore structures on loose seabed foundation; however, Young's modulus E must be dependent on the confining effective stress, rather than a constant in computation.

3D integrated numerical model for Fluid-Structures-Seabed Interaction (FSSI): Loosely deposited seabed foundation

In the past several decades, a great number of offshore structures have been constructed on loosely deposited seabed foundation because sometimes there would be no a dense seabed floor could be chosen in planned sites, for example, the breakwaters and oil platforms in the Yellow River estunary area, China. Wave-induced residual liquefaction is easy to occur in loosely deposited seabed, which brings great risk to the stability of offshore structures. In this study, we focus our attention on the 3D interaction mechanism between ocean wave, a caisson breakwater and its loosely deposited seabed foundation. A three-dimensional integrated numerical model FSSI-CAS 3D is taken as the computational tool; and the soil constitutive model: Pastor-Zienkiewicz Mark III (PZIII) proposed by Pastor et al. [16] is adopted to describe the wave-induced dynamic behavior of loose seabed soil. The numerical results indicate that the developed integrated numerical model FSSI-CAS 3D is capable of capturing a series of nonlinear phenomena, such as tilting, subsiding of breakwater, as well as residual liquefaction in loose seabed foundation etc., in the interaction process between ocean wave, a caisson breakwater and its loose seabed foundation. The purpose of this study is to provide coastal engineers with comprehensive understanding of FSSI problme involving loosely deposited seabed soil; and propose a reliable computational method to engineers involved in the design of offshore structures on loose seabed foundation.

Development of cyclicp–ycurves for laterally loaded pile based on T-bar penetration tests in clay

Offshore pile foundations are always subjected to cyclic lateral loads, which can result in the remolding and softening of the surrounding seabed soil. Cyclic T-bar penetrometer testing provides a rapid and effective method for assessing the remolded shear strength. It is widely believed that the soil strength degrades with the accumulation of plastic strain, but the strain cannot be measured. Numerical analysis described in this paper shows that the accumulated plastic displacement of the T-bar in a cyclic range of two diameters is approximately equal to its accumulated displacement. By using T-bar test data, a cyclic degradation model based on the accumulated (plastic) displacement is developed to describe the soil strength degradation at a given depth. Furthermore, an improved p–y curve model based on the cyclic degradation model is proposed to estimate the lateral response of pile under cyclic loads. The improved p–y curve model was embedded into the OpenSees program to investigate the cyclic lateral responses of soil elements and the pile. A case study was conducted to verify the improved p–y curve model by comparing it with published centrifuge experiment data. Results indicate that the improved p–y curve model based on T-bar test data is highly precise and practicable.

Numerical simulation of the seismic liquefaction mechanism in an offshore loosely deposited seabed

As a natural foundation of offshore structures, the instability of offshore seabed foundations is the dominant factor for the failure of offshore structures in strong earthquake events. It has been reported that a great number of offshore structures have failed due to soil liquefaction of Quaternary loosely deposited seabed during several recent strong seismic events. At present, countless investigations on seismic wave-induced liquefaction in on-land soil have been conducted. However, investigations on seismic wave-induced seabed soil liquefaction in an offshore environment is limited. In this study, a coupled numerical model [fluid–structure–seabed interaction (FSSI)-CAS 2D] was utilized to investigate the seismic wave-induced liquefaction mechanism in newly deposited seabed soil. The advanced soil constitutive model PZIII was adopted to describe the nonlinear dynamic behavior of loose soil. In computation, the variation of void ratio e, and related variation of soil permeability is taken into consideration; and the hydrostatic pressure acting on the seabed surface, as a boundary condition value, is automatically updated based on seabed deformation . The numerical results indicate that a loose seabed could liquefy completely, and that seabed soil liquefaction initiates at the surface of the seabed, then progresses downward. It is also indicated that the advanced soil constitutive model, Pastor–Zienkiewicz Mark III (PZIII), is capable of describing the post-liquefaction behavior of loose seabed soil to some extent.

Lab-scale impact test to investigate the pipe-soil interaction and comparative study to evaluate structural responses

ABSTRACT This study examined the dynamic response of a subsea pipeline under an impact load to determine the effect of the seabed soil. A laboratory-scale soil-based pipeline impact test was carried out to investigate the pipeline deformation/strain as well as the interaction with the soil-pipeline. In addition, an impact test was simulated using the finite element technique, and the calculated strain was compared with the experimental results. During the simulation, the pipeline was described based on an elasto-plastic analysis, and the soil was modeled using the Mohr-Coulomb fail-ure criterion. The results obtained were compared with ASME D31.8, and the differences between the analysis results and the rules were specifically investigated. Modified ASME formulae were proposed to calculate the precise structural behavior of a subsea pipeline under an impact load when considering sand- and clay-based seabed soils.

An approach to estimate the optimal depth of burial of crude oil pipelines for different marine conditions in Kuwait

Crude oil export is the main business in Kuwait. To transfer the crude oil from land to the ships moored in deeper marine water, submarine pipelines are used. Kuwait is also planning to increase the export to 4.0 million barrel/day in the future and hence need more export terminals, which in turn need more submarine pipelines. One of the challenging problems here is selection of optimum burial depth of the submarine pipeline for the prevailing design condition and soil type. The optimum burial depth of submarine pipeline is the depth at which the pipeline will be stable during the design environmental conditions. It depends on the reduction of wave forces due to burial in the seafloor. Also, the wave forces on the pipeline at any depth of burial depend on the wave characters, hydraulic properties of the sea bed soil and all other marine environmental parameters. Physical modeling is used as tool for assessing the wave forces on the pipeline model for a wide range of wave conditions, for different burial depths and for four types of cohesion-less soil types from Kuwaiti coastal area, covering hydraulic conductivity in the range of 0.286 to 1.84 mm/s. It is found that for all the four soil types, the horizontal wave force reduces with increase in depth of burial, whereas the vertical force generally increases for half buried condition, mainly due to the significant change in the magnitude as well as the phase lag between the hydrodynamic water pressures on the top and bottom of the pipe. Among the soils, well graded soil is found to be good for half burial of pipeline, since the least vertical force is experienced for this soil type. On the other hand, uniformly graded and low hydraulic conductivity soil (like Al-Koot soil with hydraulic conductivity of 0.286 mm/s) attracts the maximum vertical force for half burial case. But, such soil type is found to be good for full burial or further increase of burial, since it is found to attract less vertical wave force, when compared to the soils with high hydraulic conductivity (1.84 mm/s from Shuaiba coast). From the detailed investigations and case study analysis, the minimum safe burial depth for a 1.0 m steel pipe is 1.5 m to 2.0 m for transporting crude oil in Kuwaiti marine environment. The results of this study can be used to select the minimum safe burial depth in a range of cohesionless soils and for a range of marine wave conditions.