• Geomechanics and Engineering
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• 제7권1호
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• pp.55-73
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• 2014

The theoretical predictions of ground movements induced by tunnelling are usually based on the assumptions that the subsoil has the same soil densities. The theoretical prediction does not consider the impact of different sand soil types on the surface settlement due to tunnelling. The finite elements analysis (FEA) considers stress and strength parameters of the different sand soil densities. The tunnel construction requires the solution of large soil-structure interaction problem. In the present study, the FEA is used to model soil-tunnel system performance based on a case study to discuss surface displacement due to tunnelling. The Greater Cairo metro tunnel (Line 3) is considered in the present study as case study. The surface displacements obtained by surface displacement equation (SDE) proposed by Peck and Schmidt (1969) are presented and discussed. The main objective of this study is to capture the limitations of the parameters used in the SDE based on the FEA at different sand soil densities. The study focuses on the parameters used in the SDE based on different sand soil densities. The surface displacements obtained by the FEA are compared with those obtained by the SDE. The results discussed in this paper show that the different sand soil densities neglected in the SDE have a significant influence on the surface displacement due to tunnelling.

• Geomechanics and Engineering
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• 제37권2호
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• pp.167-178
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• 2024

The natural frequency shift under cyclic environmental loads is a key issue in the design of monopile-based offshore wind power turbines because of their dynamic sensitivity. Existing evidence reveals that the natural frequency shift of the turbine system in sand is related to the varying foundation stiffness, which is caused by soil deformation around the monopile under cyclic loads. Therefore, it is an urgent need to investigate the effect of soil deformation on the system frequency. In the present paper, three generalized geometric models that can describe soil deformation under two-way cyclic loads are proposed. On this basis, the cycling-induced changes in soil parameters around the monopile are quantified. A theoretical approach considering three-spring foundation stiffness is employed to calculate the natural frequency during cycling. Further, a parametric study is conducted to describe and evaluate the frequency shift characteristics of the system under different conditions of sand relative density, pile slenderness ratio and pile-soil relative stiffness. The results indicate that the frequency shift trends are mainly affected by the pile-soil relative stiffness. Following the relevant conclusions, a design optimization is proposed to avoid resonance of the monopile-based wind turbines during their service life.

• Journal of Ecology and Environment
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• 제39권1호
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• pp.17-29
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• 2016

We conducted the study on the relationship between the distribution of coastal sand dune plants and edaphic factors from the shoreline to inland in sand dune ecosystem. The application of TWINSPAN classification based on 10 species, led to the recognition of three vegetative groups (A-C), which associated with their habitats (foredune, hummuck in semistable zone and stable zone). The associations were separated along soil gradient far from the seashore. The relationships between species composition and environmental gradients were explained by canonical correspondence analysis (CCA). Distance from the shoreline was an important indicator to determine soil properties (pH, total ion contents, sand particle sizes, organic matters and nitrogen contents) from the seaward area to inland area and distribution pattern of coastal sand dune plants. Group A is foredune zone, characterized by Calystegia soldanella; group included typical foredune species such as Elymus mollis, Carex kobomugi, Ixeris repens, C. soldanella and Glehnia littoralis. Group B on semi-stabilized zone was characterized by Vitex rotundifolia, a perennial woody shrub. This group was associated the proportion of fine sand size (100 to 250 μm). The results on the proportion of soil particle size showed a transition in sand composition, particularly with respect to the proportion of fine sand size that occurred from the foredune ridge at 32.5 m to the Vitex rotundifolia community at 57.5 m from the shoreline. Group C on stabilized zone was characterized by Zoysia macrostachya, Lathyrus japonicus and Cynodon dactylon and were associated soil organic matter and nitrogen contents. The spatial distribution of plants in the Goraebul coastal sand dune system may result from the interactions between the plant species and environmental heterogeneity.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.896-905
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• 2006

Several soil parameters such as particle characteristics, geological element, drainage and loading conditions are influenced on the shear strength of soil. The characteristics of soil particles are important factor to the shear strength of soil. However, this component is not well considered in the determination of soil strength in Korea. The particle shape of sand was analyzed by utilizing SEM(Scanning Electron Micrograph) and compared its results in terms of aspect ratio, angularity and roughness. Based on the determined soil parameters, the ultimate bearing capacity of sandy ground was estimated by using Terzaghi bearing capacity equation.

• Geomechanics and Engineering
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• 제19권5호
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• pp.447-462
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• 2019

The vacuum preloading method has been used in many countries for ground improvement and land reclamation works. A sand cushion is required as a horizontal drainage channel for conventional vacuum preloading. In terms of the dredged-fill foundation soil, the treatment effect of the conventional vacuum preloading method is poor, particularly in Tianjin, China, where a shortage of sand exists. To solve this problem, straight-line vacuum preloading without sand is widely adopted in engineering practice to improve the foundation soil. Based on the engineering properties of dredged fill in Lingang City, Tianjin, this paper presents field instrumentation in five sections and analyzes the effect of a prefabricated vertical drain (PVD) layout and a vacuum pumping method on the soft soil ground treatment. Through the arrangement of pore water pressure gauges, settlement marks and vane shear tests, the settlement, pore water pressure and subsoil bearing capacity are analyzed to evaluate the effect of the ground treatment. This study demonstrates that straight-line vacuum preloading without sand can be suitable for areas with a high water content. Furthermore, the consolidation settlement and consolidation degree system is developed based on the grey model to predict the consolidation settlement and consolidation degree under vacuum preloading; the validity of the system is also verified.

• 한국환경복원기술학회지
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• 제5권1호
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• pp.35-50
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• 2002

This study aims to understand wetland distribution and type-specific classification features with a focus on Tumen River downstream in China by adjusting and improving the classification system used in Korea with a reference to international wetland classification systems and their criteria & methods. In this study, wetland types were determined based on hydrology, vegetation, and soil conditions, which are the most basic elements of wetlands. Also, topography analytical map, vegetation analytical map, and soil analytical map for wetland classification were developed and used based on currently available topography map, vegetation map, and soil map. In addition, codes were defined based on topography, location, hydrology, and vegetation. The result shows that, in the Tumen River downstream, wetlands are often found near natural revetment and terrace land & river-bed lakes. In the discovered wetlands, riverine, lacustrine, and inland wetlands were mostly found at system level. Riparian and human-made wetlands were also identified. At a sub-system level, perennial and seasonal wetlands were found to a similar degree. At a class level, perennial open water, herbal plants, and shrubs were mostly found and sandy plain, hydrophytes, and forest tree types were also observed. An overall detailed classification shows that a total of 17 wetland types were found and a large distribution of sand dunes and river-bed lakes, which are scarce in Northeast Asia, indicates that other rare wetland types such as palustrine seasonal sand plain wetland and lacustrine seasonal sand plain wetland may be discovered.

• 한국지반공학회논문집
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• 제33권7호
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• pp.17-28
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• 2017

본 연구에서는 건조사질토 지반에 근입된 말뚝의 동적 거동을 분석하기 위해 1g 진동대 실험을 수행하였다. 지반-말뚝 시스템의 고유 진동수를 측정한 후 고유 진동수를 기반으로 하중 진동수를 산정하고 이에 대한 거동을 분석하였다. 또한, 추가적으로 말뚝의 동적 거동에 영향을 미치는 인자를 분석하기 위하여 입력 가속도, 상부하중, 말뚝 두부 구속 조건에 따른 거동을 분석하였다. 분석결과, 하중 진동수가 지반-말뚝 시스템의 고유 진동수보다 큰 경우 상대적으로 말뚝 두부변위와 휨모멘트가 크게 발생하고 동적 p-y 곡선의 기울기가 작게 나타났다. 또한, 동적 p-y 곡선의 영향인자를 분석한 결과, 말뚝 두부구속조건은 동적 p-y 곡선의 기울기에 영향을 적게 끼침을 확인하였고, 입력가속도, 상부하중 등의 의한 관성력, 지반-말뚝 시스템의 고유 진동수와 입력 진동수의 관계 그리고 지반조건이 동적 p-y 곡선의 기울기에 큰 영향을 끼치는 것으로 확인되었다.

• 한국환경복원기술학회지
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• 제9권5호
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• pp.50-59
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• 2006

This study was initiated to investigate soil chemical properties under different soil systems. Data such as soil acidity(pH), electrical conductivity(EC), organic matter content(OMC), and cation exchange capacity(CEC) were analyzed with samples from multi-layer, USGA, and mono-layer systems. N, P, K and micronutrients were also measured. Multi-layer system was built up to 60-cm depth with rootzone layer, intermediate layer and two drainage layers. USGA system 45 centimeters deep was constructed with rootzone layer, intermediate layer and drainage layer. Mono-layer system, however, was made only with a 30-cm rootzone layer. Differences were observed in soil pH, EC, OMC, CEC and micronutrients. Soil pH was acceptable for turfgrass growth a year after establishment, being 5.5 to 6.5 in the study. Differences were greatly observed for EC among soil systems. Values of EC for multi-layer, USGA, and mono-layer systems were 39.79, 31.26 and 103.54 uS/em, respectively. The increase rate was approximately 4 to 8 times greater with mono-layer system than those with other two systems. Therefore, it was necessary to avoid micronutrient deficiency such as Fe, Mn etc. through an effective management program in mono-layer system because of its faster potential feasibility of salt accumulation. The greatest OMC was associated with USGA system, being 0.97% which was 11% over that of the other systems. Slight differences were observed for CEC among them. Mono-layer system produced 1.45 me/100g, 10.3% and 8.9% lower in CEC than those of multi-layer and USGA system, respectively. Micronutrients such as Fe, Zn, and Mn etc. were below the level required for turf growth, regardless of soil systems. It was considered that one year after turf establishment was not enough to build up micronutrients in sand-based soil systems to the normal level for a turf growth. These results demonstrate that intensive management program including grow-in concept fertilization should be integrated into sand-based soil systems, even after a year in establishment. Regular nutrient monitoring by soil analyses is a strong necessity to decide the kinds and amount of fertilizer. Also, strategic management program must be selectively employed according to sports turf soil systems.

• Geomechanics and Engineering
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• 제31권3호
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• pp.291-304
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• 2022

Maximum shear modulus (G_max or G₀) is an important soil property useful for many engineering applications, such as the analysis of soil-structure interactions, soil stability, liquefaction evaluation, ground deformation and performance of seismic design. In the current study, bender element (BE) tests are used to evaluate the effect of the void ratio, effective confining pressure, grading characteristics (D₅₀, C_u and C_c), anisotropic consolidation and initial fabric anisotropy produced during specimen preparation on the G_max of sand-gravel mixtures. Based on the tests results, an empirical equation is proposed to predict G_max in granular soils, evaluated by the experimental data. The artificial neural network (ANN) and Adaptive Neuro Fuzzy Inference System (ANFIS) models were also applied. Coefficient of determination (R²) and Root Mean Square Error (RMSE) between predicted and measured values of G_max were calculated for the empirical equation, ANN and ANFIS. The results indicate that all methods accuracy is high; however, ANFIS achieves the highest accuracy amongst the presented methods.

• KIEAE Journal
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• 제16권1호
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• pp.73-79
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• 2016

This study aimed to investigate the flood prevention effect expected from the afforestation of a large area metal roof of an industrial complex located in an area prone to floods in the rainwater outflow reduction aspect through computer simulation based on soil, which is a key element of the system. In order to conduct a more realistic simulation, the properties of the surveyed soil were generated through substantive analysis, soil texture analysis, and saxton method. A comparative performance evaluation was conducted by using soil depth and ponding depth, which are key elements of the system, as variables. The study result showed that during the heavy rainfall period, the bottom ash artificial soil had 61% rainwater outflow reduction effect, which was 11% higher than the SWMM standard sand.