Role of piles in mitigating the movement of pipes in soft grounds during embankment loading     

Won Pyo Hong  Jae Hong Kim 《Marine Georesources & Geotechnology》2013,31(9):1019-1031

Abstract

Pipes buried in soft ground can be damaged due to the vertical and lateral movement of the ground during the construction of the embankment. To investigate such a movement of the soft ground, full-scale tests using embankment piles and stabilizing piles were conducted for 70?days. A pile-supported embankment has been used to reduce the deformation of soft ground by transferring the embankment load through piles to the firm layer below the soft ground, whereas stabilizing piles have been employed to resist the lateral earth pressure that is induced in soft ground by embankment loads. The Coupling Area (CA), which was defined as the quantitative index to determine the resistance effect of both settlement and lateral flow of the soft ground when the embankment was reinforced, is adapted. The analysis results of the CA indicate that the piled embankment was more effective for preventing the damage to buried pipe installed near the embankment, while the stabilizing piles had almost the same effect as the piled embankment when the pipe was buried far away from the embankment.  相似文献   

Nitrogen budget of the eelgrass, Zostera marina in a bay system on the south coast of Korea     

Sang Rul Park  Young Kyun Kim  Seung Hyeon Kim  Kun-Seop Lee 《Ocean Science Journal》2013,48(4):301-310

Above- and below-ground productivities and tissue N content were measured monthly to quantify N incorporation to sustain eelgrass growth in Koje Bay on the south coast of Korea from January to December 2002. N acquisition was also estimated through measurements of N uptake kinetics, tissue biomass, and in situ inorganic N concentrations in water column and sediments. Above- and below-ground productivities were highest in summer and lowest in late fall and winter. Leaf tissue N content was highest in December and lowest in July, while rhizome tissue N content was highest in October and lowest in April. Estimated monthly N incorporation by leaf tissues based on the leaf productivity and N content ranged from 0.4 g N m^?2 month^?1 in November to 2.0 g N m^?2 month^?1 in May. N incorporation by below-ground tissues ranged from 0.1 g N m^?2 month^?1 in February to 0.2 g N m^?2 month^?1 in October. Annual whole plant N incorporation was 14.5 g N m^?2 y^?1, and N incorporation by leaf tissues accounted for about 87 % of total N incorporation. Maximum uptake rate (V _max ) and half saturation constant (K _m ) of leaf NH₄ ⁺ uptake were significantly lower than those of root NH₄ ⁺ uptake. Above- and below-ground biomass ranged from 20.8 g DW m^?2 and 8.6 g DW m^?2 in winter to 350.0 g DW m^?2 and 81.3 g DW m^?2 in spring, respectively. NH₄ ⁺ concentrations varied from 0.2 to 4.3 mM in water column and from 93.0 to 551.7 mM in sediment pore water. Based on these measurements, annual N acquisition by root tissues contributed slightly higher than that by leaf tissues to total plant N acquisition. During winter, monthly leaf N acquisition was lower than monthly leaf N incorporation. This implies that Z. marina has internal nitrogen retention system to offset the shortage and excess of nitrogen.  相似文献   

Description of a small goby, Trimma grammistes (Perciformes: Gobiidae), from Jeju Island, Korea     

Byung Jik Kim  Seung-Ho Choi  Sung Kim 《Ocean Science Journal》2013,48(2):235-238

A small goby, Trimma grammistes, was described in detail as the first reliable record from Korea based on 10 specimens (27.8～34.0 mm SL) collected from the coastal waters of Jeju Island. The species is easily differentiated from congeners by having no scales on the predorsal region, VI-I, 10 dorsal fin rays modally, I, 10 anal fin rays, 18 pectoral fin rays, 27～30 longitudinal scales as well as two dark longitudinal bands on the body.  相似文献   

Behavior of soil plugs in open‐ended model piles driven into sands     

Kyu‐Ho Paik  Seung‐Rae Lee 《Marine Georesources & Geotechnology》2013,31(4):353-373

Calibration chamber tests were conducted on open‐ended model piles driven into dried siliceous sands with different soil conditions in order to clarify the effect of soil conditions on load transfer mechanism in the soil plug. The model pile used in the test series was devised so that the bearing capacity of an open‐ended pile could be measured as three components: outside shaft resistance, plug resistance, and tip resistance. Under the assumption that the unit shaft resistance due to pile‐soil plug interaction varies linearly near the pile tip, the plug resistance was estimated. The plug capacity, which was defined as the plug resistance at ultimate condition, is mainly dependent on the ambient lateral pressure and relative density. The length of wedged plug that transfers the load decreases with the decrease of relative density, but it is independent of the ambient pressure and penetration depth. Under several assumptions, the value of earth pressure coefficient in the soil plug can be calculated. It gradually reduces with increase in the longitudinal distance from the pile tip. At the bottom of the soil plug, it tends to decrease with increase in the penetration depth and relative density, and to increase with the increase of ambient pressure. This may be attributed to (1) the decrease of friction angle as a result of increase in the effective vertical stress, (2) the difference in the dilation degree of the soil plug during driving with ambient pressures, and (3) the difference in compaction degree of soil plug during driving with relative densities. Based on the test results, an empirical equation was suggested to compute the earth pressure coefficient to be used in the calculation of plug capacity using one‐dimensional analysis, and it produces proper plug capacities for all soil conditions.  相似文献   

Changing times: Preface     

Ronald C. Chaney Editor‐in‐Chief 《Marine Georesources & Geotechnology》2013,31(3-4):3-4

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Assessment of Dynamic Characteristics for Compaction Piles with Geophysical Logging in Soft Ground     

K. H. Lee  S. K. Kim  G. G. Yea 《Marine Georesources & Geotechnology》2013,31(1):62-75

In this paper, a case study was performed on a sand compaction pile (SCP) and a gravel compaction pile (GCP) to estimate the dynamic characteristics and the improvement effect of soft ground. The dynamic elastic modulus, shear modulus, bulk modulus, and Poisson's ratio were estimated and the dynamic characteristics were analyzed using the compression and shear wave velocity of the improved ground based on the results of suspension P- and S-wave (PS) logging. The results revealed that the dynamic properties were increased in the order of unimproved subsoil and improved subsoil using SCP and GCP. The increase in the effects of dynamic properties with each replacement ratio of SCP was not large, whereas a good increase in the effects was observed in the case of the improved subsoil with GCP. Consequently, it was presented that the resistance characteristics against the seismic loading of GCP are excellent. As a result of analyzing the density distribution of the improved subsoil through density field logging, the overall density distribution gradually exhibits increasing trends in the order of unimproved subsoil and improved subsoil with SCP and GCP. Thus, the improvement effect of GCP was relatively high in comparison with the same replacement ratio of SCP.  相似文献   

Geotechnical characterization of slump scars,eroded slopes,and correlated deposits on continental margins: Gulf of Lions,Western Mediterranean sea     

M. Canals‐Artigas  B. Chassefiere 《Marine Georesources & Geotechnology》2013,31(3):159-178

Abstract

Vertical variations of geotechnical properties in the uppermost sediment layers characterize the main sedimentary processes acting on the construction and destruction of progressive‐type continental slopes. In the Gulf of Lions, the original thicknesses and distribution of the uppermost sedimentary layers of the continental slope and rise, which consist of Holocene muds overlying Pleistocene muds, have been greatly modified by erosion and several kinds of slope failure processes. Each process is typified through sets of geotechnical properties measured in the eroded or slumped sections and in the associated sediment accumulations.

In slump scars, the water‐rich Holocene muds lie on fine, overconsolidated, Pleistocene muds with high plasticity and low shear strength. In bottom current‐eroded slopes, where modern sedimentation is extremely reduced, the Pleistocene muds frequently outcrop and may sometimes be overlain by a very thin layer of Holocene muds. The Pleistocene muds of eroded slopes are overconsolidated and more silty and less plastic than the Pleistocene muds from slopes affected by slope failure, their shear strength being 10 times greater.

Deposits at the toe of slumps are very often formed by several superposed three‐layer units (triplets of interstratified Holocene, transitional, and Pleistocene layers) issued from retrogressive slumping occurring in the slump scars above their head area. The main body of each layer is then relatively undisturbed, showing the usual burial geotechnical gradients due to overburden pressure (i.e., decrease of water content and increase of unit weight and shear strength). At the toe of bottom current‐eroded slopes, a thick and homogeneous layer of Holocene muds overlies the Pleistocene muds; this Holocene layer has unappreciable burial depth gradient of its geotechnical parameters because of a high rate of modem and continuous deposition.  相似文献   

Experimental Evaluation of Leaching Effects on the Compressibility of Marine Clay and its Strain Rate Dependency     

Yun-Tae Kim  Thanh-Hai Do 《Marine Georesources & Geotechnology》2013,31(1):16-29

This study investigated how leaching affects compressibility behavior of marine clay and its strain rate dependency based on laboratory tests using three pairs of specimens. Each pair of specimens consisted of leached and unleached samples with identical geotechnical properties except soil salinity. The behavior characteristics of the leached and unleached specimens were evaluated using several series of constant rate-of-strain (CRS) tests with differing strain rates. The results revealed that the compressibility of leached clay increased as its salinity decreased. However, void ratio, Atterberg limits, and preconsolidation pressure in leached samples were lower than those in unleached clay. The increased compressibility and decreased preconsolidation pressure may be induced from a weakening of the interparticle bonds in the leached soil skeleton. The CRS test results with differing strain rates revealed that higher strain rates corresponded with higher levels of effective stress and higher apparent preconsolidation pressure in both leached and unleached clays.  相似文献   

Assessment of Risk Due to Debris Flow and Its Application to a Marine Environment     

Sungduk Kim 《Marine Georesources & Geotechnology》2013,31(6):572-578

The purpose of this study is to evaluate the behavior and mechanism of a debris flow on various slopes through numerical simulation. The numerical simulation consisted of using equations related to mass conservation and momentum conservation in order to consider erosion and deposition, and the Finite Difference Method was applied. As the inflow water discharge in the upstream of the channel increases, the curve of the water discharge exhibits instability and, as time passes, the fluctuation of the high water discharge continues. In regions where the mountain areas and the ocean are connected, it is deduced that the high level of sediment concentration can greatly affect the environment surrounding the ocean. The numerical model of this study was applied in Kangwon Province of South Korea. The results show that when the debris flow reaches downstream, the flow discharge and water flow depth increase. Erosion occurs more than deposition and much of the sediment runs off downstream. The result of the simulation performed at point of sediment discharge runoff is 114,216 m³. This study will provide useful information in predicting disasters caused by debris flow and in planning for various countermeasures to prevent debris-flow-related disasters.  相似文献   

Mechanical Characteristics of Light-Weighted Soils Using Dredged Materials     

Gil-Lim Yoonz  Sang-Soo Jeon  Byung-Tak Kim 《Marine Georesources & Geotechnology》2013,31(4):215-229

This study investigates the mechanical characteristics of light-weighted soils (LWS) consisting of expanded polystyrene (EPS), dredged clays, and cement through both unconfined and triaxial compression tests. The mechanical characteristics of the compressive strength of LWS are analyzed with varying initial water contents of dredged clays, EPS ratio, cement ratio, and curing pressure. In the triaxial compression test, it is found that the compressive strength of LWS associated with EPS is independent on the effective confining pressure. When both EPS ratio is less than 2% and cement ratio is more than 2%, the compressive strength rapidly decreases after the ultimate value. This signifies that the compressive strength-strain behavior is quite similar to that of the cemented soil. The ground improved by LWS has the compressive strength of 200 kPa associated with the optimized EPS ratio of 3–4% and initial water content of 165–175%. The ultimate compressive strength under both triaxial and unconfined compression tests is almost constant for a cement ratio of up to 2%.  相似文献