Wide-area Land Subsidence of Kashiwazaki Plain due to the 2007 Niigata-ken Chuetsu-Oki Earthquake
S. Ohtsuka, K. Isobe, and Y. Fukumoto
ABSTRACT: Wide-area land subsidence occurred across the Kashiwazaki Plain, Niigata, Japan after the 2007 Niigata-ken Chuetsu-Oki Earthquake. The stratified ground subsidence meter clearly showed that a thick clayey layer had caused this subsidence after the earthquake. To examine the ground conditions, a boring survey was conducted at the site and the physical and mechanical properties of the ground were tested. Although leveling surveys are insufficient for surveying the behavior of the ground, the measurement data obtained at various points from these surveys are meritorious for grasping the spatial distribution and the time-dependent property of the land subsidence. In this study, by analyzing the instantaneous and the long-term amounts of land subsidence at each point from the time-series observation data, the correlation between geology and topography is reported and the cause of the land subsidence of the clayey soils after the earthquake is discussed. It is clarified that the existence of a marine clay layer greatly affected the long-term subsidence of the land.
KEYWORDS: Land subsidence, Earthquake, Clayey soils, Terrain classification.
An Expanded Polystyrene Foam (EPS) Road Robust to Successive Great Kumamoto Earthquakes in 2016
K. Yasuhara, H. Tsukamoto, K. Taneichi, T. Konami, and T. Kubota
ABSTRACT: This paper describes a case in which no complete demolishment was observed in a geofoam (expanded polystyrene foam EPS) embankment. Used for local roads situated over active faults at a mountainous site in Mashiki Town, Kumamoto, Japan, the EPS withstood two successive strong earthquakes that struck Kumamoto and Oita prefectures in 2015. The EPS blocks of this EPS embankment were markedly shifted sideways both horizontally and vertically because earthquake-caused landslides occurred behind the EPS fills. Nevertheless, only a part of the EPS embankment collapsed, causing no damage to the temple nearby. Thereafter, the road surface was remediated temporarily immediately after the earthquakes and was maintained for the opening of traffic. This case demonstrates that EPS presents great benefits: most importantly, the partly collapsed EPS road was put into practical use as a temporary road supporting the daily life of local residents. This report describes an engineering perspective of why the road was not collapsed completely. Future issues to be considered by local governments and engineering institutions are explained for the preparation of great earthquake countermeasures.
KEYWORDS: Earthquake, Geofoam block, Local road, Reuse, Stability.
Deformation and Cyclic Strength Characteristics of Loose and Medium-Dense Clean Sand under Sloping Ground Conditions: Insights from Cyclic Undrained Torsional Shear Tests with Static Shear
G. Chiaro, M. Umar, T. Kiyota, and J. Koseki
ABSTRACT: The effects of liquefaction on sloping ground often include the development of extremely large deformation. Although such phenomenon has been repeatedly observed following major earthquakes, the triggering conditions are not fully understood yet. To provide new insights into this issue, in this paper, results of two series of large-strain undrained cyclic torsional shear tests with initial static shear conducted on loose and medium-dense Toyoura sand specimens (relative density of 25-30% and 44-48%) are presented and analyzed. The post-liquefaction response of Toyoura sand is assessed in terms of failure modes and cyclic resistance up to 50% single amplitude shear strain. It is shown that, depending on the combined magnitude of static and cyclic shear stresses, a sand in sloping ground will likely experience a sudden development of large shear deformation (flow deformation) if initial liquefaction takes place, or a more progressive accumulation of large residual deformation, which yet may bring sand to failure, when the onset of initial liquefaction is not achieved.
KEYWORDS: Flow deformation, Liquefaction, Residual deformation, Shear failure, Simple shear, Sloping ground.
Resilient Deformation Characteristics of Unsaturated Subgrade Materials of Rail Tracks under Cyclic Moving Wheel Loads
T. Ishikawa, B. Dareeju, C. Gallage, and L. Tianshu
ABSTRACT: Water content of rail track subgrade materials fluctuates throughout the year due to the number of wetting and drying cycles, introducing unsaturated properties into the subgrade. Conservative rail track design guidelines are, however, mainly based on two extreme saturation conditions: fully dried or fully saturated. Current knowledge on the effects of subgrade water content on residual and resilient behaviour of the track foundation under the effects of Principal Stress Axis Rotation (PSAR) is limited and the potential of expansibility of foundation materials further upsurge the complexities towards the designing of the rail tracks. This study demonstrates the contributions of the PSAR on the resilient behaviour of foundation materials. Three different materials, including an expansive soil type have been subjected to drained cyclic vertical and torsional shear tests in a Modified Multi-Ring Shear (MMRS) apparatus and it is concluded that the resilient behaviour of the foundation materials is functions of the PSAR, material type, water content, and potential of expansibility.
KEYWORDS: Unsaturated foundation materials, Principal stress axis rotation, Resilient behavior, Expansive potential.
Cyclic Behaviour and Dynamic Properties of Texcoco Clays near Mexico City
Efraín Ovando, Zaira Hernández, Osvaldo Flores, and Alfonso Fernández
ABSTRACT: The soft clayey soils of the Former Texcoco Lake, a few kilometres north of Mexico City are highly compressible materials that exhibit very low shear strengths and are also characterized by having extremely high water contents. These soils have been studied extensively in the past but a revision of its properties and characteristics in now in order because large infrastructure works are underway or are being planned to operate in the zone in the near future. This paper presents an overview of some of the results of recent research into the dynamic behaviour of Texcoco Clays carried out at the National University of Mexico. We present the results of one way consolidated-undrained cyclic triaxial tests in which we varied cyclic amplitude as well applied stresses using high quality samples retrieved from the site. Results are also expressed in terms of accumulated strains and in terms of the evolution of pore pressure during cyclic loading. We complement the results of these tests with those obtained from torsional resonant column tests in which we assess an analytical model to express the stiffness-strain and damping-strain characteristics of these materials. We also look at the relationship of small strain stiffnesses obtained in resonant column tests and those found from the results of bender element measurements and from the results of field measurements using the suspension logging technique. We also put forth correlations between the dynamic parameters obtained in the lab and in the field with data from CPT tests. Finally, we discuss the significance of these tests bearing in mind that the site is subjected to regional subsidence due to the exploitation of the aquifers that underlie the clayey strata.
KEYWORDS: Cyclic behavior of soft clays, Properties of Texcoco clays, México City, Test on cyclic triaxial cells and resonant column.
Engineering Properties of Mangking Sandstone
Ainuddin Yasin and Jasmi Ab Talib
ABSTRACT: This project was intended to characterize the engineering properties of Mangking Sandstone Formation in Maran, Pahang. The main lithology is fine-grained white to light grey sandstone. The engineering properties of Mangking Sandstone was assessed by applying geological technique which is discontinuity survey and geomechanical techniques including Schmidt Hammer test, Acoustic Velocity test, Uniaxial Compressive Strength (UCS) test, Brazilian Tensile Strength test and Point Load Strength test. The Rock Mass Rating (RMR) system was applied to the rock mass based on its geological discontinuity and geomechanical information to assess the quality of the rock. Slope Mass Rating (SMR) was applied to assess the stability of the slope. The RMR values range from 73 to 78 which place the Mangking Sandstone in Maran area in Class II (good rock). The SMR values place the rock slope of Mangking Sandstone in Maran area in Class II (stable slope).
KEYWORDS: Sandstone, Geology, Geomechanics, Mangking, Engineering.
Analysis of Cracking Behavior of Composite Landfill Liners
Abdullah All Noman and Islam M. Rafizul
ABSTRACT: This study aims to quantify the cracking behaviour of composite landfill liners easily, quickly and in better mode using image analysis technique. The disturbed soil samples were collected from a selected waste disposal site at Rajbandh, Khulna, Bangladesh. The mixing proportions of 10, 20, 30, 40, 50 and 60% of brick dust as well as 20, 30, 40, 50, 60 and 70% of fly ash by dry weight with soil samples were used to prepare composite liners. Steel circular molds having 30 cm diameter with different thicknesses of 10, 20 and 30 mm were used. The amount of water content equal to liquid limit, plastic limit and optimum moisture content of mixing soil were considered. The wetting-drying cycles were subjected on specimens to simulate the field behavior of liners. The cracking behaviour such as crack intensity factor (CIF), crack density factor (CDF) and crack areas were measured through MATLAB and ImageJ technique. The maximum CIF, CDF and crack area were obtained in control soil. The CIF, CDF and crack area decreases with the increase of fly ash and brick dust content in liners. Result reveals CIF, CDF and crack area increase with the increase of water content. The liners with water content equal to liquid limit showed maximum CIF, CDF and crack area. Moreover, the CIF and crack area decrease with the increase of specimen thickness except for CDF. With the multiple wetting-drying cycles experiment, the amount of cracking did not significantly change after 2nd wetting-drying cycle.
KEYWORDS: Composite liners, Desiccation, Cracking behavior, ImageJ, MATLAB.
Prediction of California Bearing Ratio (CBR) from Index Properties of Fine-Grained Soil
Arunav Chakraborty and Anasuya Goswami
ABSTRACT: The California Bearing Ratio (CBR) value is an important variable in pavement design since it determines the strength of the subgrade soils. However, it should be noted that the CBR test is arduous and time-consuming. As a result, this work attempts to establish relationships between CBR and several soil index parameters such as liquid limit (LL), plastic limit (PL), optimum moisture content (OMC), and maximum dry density (MDD). Regression analysis and neural networks were used to develop three prediction models for correlating soaked CBR values with LL, PL, OMC, and MDD for soil samples taken from different locations in Guwahati, Assam, India. Because Assam is prone to flooding, and some rural roads are inundated for two to three days under water, a soaked CBR is considered. According to the results, ANN can more accurately predict soaked CBR values.
KEYWORDS: California bearing ratio, Artificial neural network, Multiple regression, Optimum moisture content, Maximum dry density.
Theoretical Study on the Influence of Degradation and Compression Parameters on Gas Pressure in Municipal Solid Waste Landfill
G. Zeng and and J. Ma
ABSTRACT: Gas pressure is of great significance to the safe management and operation in a landfill. In this paper, a mathematical model for gas pressure simulation in a landfill was developed and the effects of degradation and compression parameters on gas pressure were studied. The results showed that gas pressure in landfill was continuously decreased under the action of extraction pressure. The internal gas pressure in horizontal direction was smaller than that in vertical direction at the same position due to the heterogeneity and anisotropy of refuse dump. Gas pressure in landfill increased with the increase of compression coefficient, biodegradation strain and biodegradation rate constant. The internal gas pressure was most significantly affected by compression coefficient, followed by biodegradation strain, and biodegradation rate constant had the least influence. The influence ranges were 60 kPa, 6 kPa and 3 kPa, respectively.
KEYWORDS: Landfill, Gas pressure, Mathematical model, Simulation rule.
Assessments of Soil Parameter Reduction Coefficients from One-Dimensional Ground Response Analyses
D.W. Chang, J.F. Li, and Y.S. Lin
ABSTRACT: Soil parameter reduction coefficient (DE) has been suggested by Architecture Institute of Japan (AIJ) and Japan Road Association (JRA) for over twenty years. The reduction coefficient denoted as DE was used to reduce stiffness and/or strength parameters of the soil due to liquefaction caused by earthquakes. This study discusses the observations based on soil parameter reduction coefficients calculated from one-dimensional dynamic responses on artificial ground sites under horizontal earthquakes. A lumped mass model of horizontal sand layers is used. Soil liquefaction is modeled using the UBCSAND model. The factor of safety against liquefaction and the cyclic strength ratio for soils at various depths are calculated from the mechanical analyses to find the reduction factors based on the suggestions from JRA and AIJ. In addition, the ratio between the degraded shear modulus and the initial shear modulus of the soils are computed and compared to the reduction coefficients found varying the influence factors.
KEYWORDS: Liquefaction, Soil parameter reduction coefficient, Ground response Analysis, UBCSAND model.
