Saturated Sand Layer Research Articles

Liquefaction Potential Analysis of Reusep Prestress Bridge in Pidie Jaya due to 6.4 Mw Earthquake

Pidie Jaya is one of the districts in Aceh Province – Indonesia. On December 7, 2016, Pidie Jaya experienced a shallow 6.4 Mw earthquake which destroyed some vital buildings and also human loss. Based on preliminary field investigation, some geological damages like soil movement, soil cracks, and liquefactions occur because of the earthquake. Some liquefaction phenomena scattered in the area of Ulim, Panteraja, Meunasah Balek, Manohara Beach and Sagoe Trienggadeng. An evidence of liquefaction in Pidie Jaya area was displayed in this research based on several literature review. Furthermore, these paper aims to identify liquefaction possibilities in Trienggadeng Reusep Prestress Bridge based on a geotechnical investigation of N-SPT and some seismic data by using Kishida method. The surrounded area of the bridge was first evaluated in terms of geological setting, tectonics and seismic activity related to 6.4Mw of the previous earthquake. Furthermore, it was found from the soil profile that the studied area has a potency of liquefaction because of several saturated sand layers and high groundwater level. Effective overburden pressure of sand layers was calculated and plotted with N-SPT value to determine the possibility of liquefaction. The result shows that liquefaction potential shows high possibility for sand dominant layers both from bor-log 1 in 17.5 m and 25 m depths, and bor-log 2 in the depth of 17 m and 26.5 m.

Effect of the combined action of lateral load and axial load on the pile instability in liquefiable soils

Even with modern design guidelines, collapse of pile-supported structures in liquefiable deposits are still observed after strong earthquakes, and buckling instability of piles has been cited as a possible mechanism of failure in liquefiable soils. However, the buckling failure of pile under the combined action of lateral load and axial load has received little attention. This paper presents a shake-table test to study the failure mechanism of an end-bearing pile partly embedded in a saturated sand layer. It is found that pile with a large mass at the top failed in buckling after the soil fully liquefied. In addition, a pseudo-static analysis method is proposed to evaluate the buckling instability of the pile under the combination of lateral and axial load. The buckling load of the pile was found to decrease with the increase in lateral inertial load. It is hence important for the designers to consider the level of lateral loading during buckling analysis of pile in liquefiable ground. Finally, a possible boundary for safe design is proposed to avoid buckling failure of the pile while considering the effect of inertial load.

Pressurized clay injection method using kaolinite for controlling groundwater of a saturated sand layer

In tunnel construction in the city area, NATM method is adopted for construction by the limitation of the construction condition. When classifies roughly in supporting method of construction, there are against the spring water, face stability, ground surface subsidence, cement, water glass and urethane are usually used for grouting material against the spring water, but there is the concern, such as expensive and high load on the environment because of artificial materials. On the other hand, Kaolinite is a natural material, there is less load on the environment, and many merits in the processing of the excavated muck. Therefore, we focused a pressurized clay injection method by using the above-mentioned characteristics and applied this to the construction of the underground. In this paper, the availability of the injection a fluid with a dispersion of kaolinite was discussed to summarize the applicability for controlling groundwater of the saturated sand layer. Specifically, a one-dimensional column test was conducted under the high hydraulic gradient. As a result, it was shown the possibility of effecting of decreasing hydraulic conductivity at less than one-order. Consequently, it is concluded hydraulic conductivity of sand layer was able to be reduced by Kaoline clay suspension.

A practical bio-based reversible permeability control for saturated sands

There is a need for an eco-friendly in situ reversible permeability control that reduces the number of artificial materials used to achieve a saturated sand layer. This study investigates such a control using a method that causes calcite precipitation and decalcification based on the metabolism of carbon sources. This generates carbon dioxide and organic acid and creates and detaches a biofilm using dry yeast and sodium hypochlorite. A pilot test determined the optimal chemical composition for this from a few different concentrations of carbon sources that begin the permeability reduction and recovery process. Following this, the main test (the permeability test) was conducted on a water sample taken from an agricultural area, which was combined with chemicals and dry yeast in a permeameter column. Permeability tests were carried out under three conditions (untreated, treated and treated combined with a biofilm detachment phase). The results suggest that (a) calcite precipitation induced by microbes, combined with bioclogging, can control the reduction in soil permeability and (b) a biofilm remover (sodium hypochlorite) and decalcification based on the organic acid created from the metabolism of carbon sources effectively recover the soil permeability to its initial state.

The mechanisms of a loess landslide triggered by diversion-based irrigation: a case study of the South Jingyang Platform, China

Continuous use of diversion-based irrigation has been associated with an increase in the frequency of loess landslides on the South Jingyang Platform, Shaanxi, China. A loess landslide event with a maximum sliding distance of 278 m occurred near the village of Miaodian on May 26, 2015. This landslide event was characterized by four individual landslides. Field investigations, geological exploration, numerical simulation, isotropically consolidated undrained (ICU) triaxial tests, and ring shear tests were conducted to identify its initiation and movement mechanisms. The ICU tests revealed that saturated loess samples were highly liquefiable. High pore water pressure was quickly produced and deviation stress increased the highest value even at low values of axial strain. Geological investigations revealed that cracks penetrated into the saturated zone from the ground surface, and simulation results revealed that these cracks played a dominant role in the infiltration of surface water and led to a rise in the groundwater table. When the infiltration recharge exceeds the holding capacity of the paleosol, the latter behaves as aquifuge under relatively undrained conditions. This process results in the accumulation of water at the bottom of the loess layer, thereby contributing to soil liquefaction and landslide initiation. The ring shear tests revealed that the saturated sand layer of the landslide substrates was subjected to easily inducible high pore water pressure under undrained conditions which led to the thrusting of the sand layer onto the deposit surface and explains the high speed and long runout distance of this landslide.

Integrated Geophysical and Geological Mapping of the Lithological and Geological Structures at a Proposed Generator Site

The discovery of oil in commercial quantity in Ghana has led to increase in infrastructural development to provide the needed services to the oil industry. The siting of these industries requires the characterization of the subsurface to determine its suitability to host these facilities. It is in this line that seismic refraction and geo-electrical surveys were conducted on a site near Takoradi, Ghana that has been planned to host a generator and its appurtenances for the oil industry. The objective of the survey was to provide subsurface information critical for the design of earthing system for the proposed generator plant and its appurtenances. The ABEM SAS4000 Terrameter with the Lund imaging system and a 24-channel ABEM Terraloc MK6 were respectively used for the electrical and seismic refraction data collection. The seismic refraction and resistivity results identify three lithological units namely, dry gravel, sand and silty clay layer, water saturated sand and silty clay layer and granodiorites basement rocks. The first layer has a thickness of 10 m and the second layer with thickness in the range of 5 to 10 m. The lithological classifications as obtained from these results correlate with the drill logs. Electrical grounding will be suitable at a depth of 10 m beneath resistivity profile two at a distance between 32 to 52 m.

Remediation of liquefaction effects for an embankment using soil-cement walls: Centrifuge and numerical modeling

Numerical simulations of a centrifuge model test of an embankment on a liquefiable foundation layer treated with soil-cement walls are presented. The centrifuge model was tested on a 9-m radius centrifuge and corresponded to a 28 m tall embankment underlain by a 9 m thick saturated loose sand layer. Soil-cement walls were constructed through the loose sand layer over a 30 m long section near the toe of the embankment and covered with a 7.5 m tall berm. The model was shaken with a scaled earthquake motion having peak horizontal base accelerations of 0.05 g, 0.26 g, and 0.54 g in the first, second, and third events, respectively. The latter two shaking events caused liquefaction in the loose sand layer. Crack detectors embedded in the soil-cement walls showed that they developed only minor cracks in the second shaking event, but sheared through their full length in the last shaking event. The results of the centrifuge model test and two-dimensional nonlinear dynamic simulations are compared for the two stronger shaking events using procedures common in engineering practice. The effects of various input parameters and approximations on simulation results are examined. Capabilities and limitations in the two-dimensional simulations of soil-cement wall reinforcement systems, with both liquefaction and soil-cement cracking effects, are discussed. Implications for practice are discussed.

Preliminary study of soil liquefaction hazard at Terengganu shoreline, Peninsular Malaysia

Terengganu is a shoreline state located in Peninsular Malaysia which is a growing hub for port industries and tourism centre. The northern part offers pristine settings of a relax beach areas whereas the southern part are observed to be a growing centre for development. The serious erosion on soil deposit along the beach line presents vulnerable soil condition to soil liquefaction consists of sandy with low plasticity and shallow ground water. Moreover, local earthquake from nearby fault have present significant tremors over the past few years which need to be considered in the land usage or future development in catering the seismic loading. Liquefaction analysis based on field standard penetration of soil is applied on 546 boreholes scattered along the shoreline areas ranging 244 km of shoreline stretch. Based on simplified approach, it is found that more than 70% of the studied areas pose high liquefaction potential since there are saturated loose sand and silt deposits layer ranges at depth 3 m and up to 20 m. The presence of clay deposits and hard stratum at the remaining 30% of the studied areas shows good resistance to soil liquefaction hence making the area less significant to liquefaction hazard. Result indicates that liquefaction improving technique is advisable in future development of shoreline areas of Terengganu state.

Centrifuge tests to assess seismic site response of partially saturated sand layers

Seismic response of unsaturated soil layers may differ from that of saturated or dry soil deposits. A set of centrifuge experiments was conducted to study the influence of partial saturation on seismic response of sand layers under scaled Northridge earthquake motion. Steady state infiltration was implemented to control and provide uniform degree of saturation profiles in depth. The amplification of peak ground acceleration at the soil surface was inversely proportional to the degree of saturation, especially in low period range. The cumulative intensity amplification of the motion was also higher in unsaturated soils with higher suctions. The lateral deformation and surface settlement of partially saturated sand with higher stiffness were generally lower than that in dry soil. Although neglecting the effect of partial saturation in sand layers might be conservative with respect to seismic deformations, it may result in underestimating the surface design spectra.

Transport and retention of TiO2 and polystyrene nanoparticles during drainage from tall heterogeneous layered columns

Recent developments in nanotechnology have seen an increase in the use of manufactured nanomaterials. Although their unique physicochemical properties are desirable for many products and applications, concern continues to exist about their environmental fate and potential to cause risk to human and ecological health. The purpose of this work was to examine one aspect of nanomaterial environmental fate: transport and retention in the unsaturated zone during drainage. The work made use of tall segmented columns packed with layers of two different porous media, one medium sand and one fine sand. The use of tall columns allowed drainage experiments to be conducted where the water table remained within the height of the column, permitting control of final saturation profiles without the need for capillary barrier membranes which can potentially complicate analyses. Experiments were conducted with titanium dioxide (TiO2) and polystyrene nanomaterials. For the strongly negatively-charged polystyrene nanomaterials, little retention was observed under the conditions studied. For the TiO2 nanomaterials, results of the work suggest that while saturated fine sand layers may retain more nanomaterials than saturated coarse sand layers, significantly greater retention is possible in unsaturated media. Furthermore, unsaturated medium sand layers exhibited significantly greater retention than adjacent saturated fine sand layers when present at low saturations high above the water table. Retention by unsaturated media were found to correlate strongly with elevation. Free drainage experiments including both primary and secondary drainages in homogeneous columns showed evidence of redistribution during imbibition and secondary drainage, but still showed substantial unsaturated retention of TiO2 nanoparticles high in the column, despite re-saturation with- and drainage of nanoparticle-free water.

Numerical investigation on the behavior of the gravity waterfront structures under earthquake loading

Lateral Spreading, which usually occurs as a consequence of liquefaction in gently sloped loose saturated sand layers, is known to be a major source of earthquake-induced damages to structures such as quay walls, bridge piers, pipelines, and highway/railways. Therefore evaluation of the liquefaction potential and using appropriate methods for prediction of the adverse consequences of lateral spreading is of great importance. In this study, numerical modeling has been used to study lateral spreading phenomenon behind rigid waterfront structures. Coupled dynamic field equations of the extended Biot’s theory with u–P formulation are used for simulating the phenomenon. A fully coupled finite element code utilizing a critical state two-surface plasticity constitutive model has been applied and variation of permeability coefficient during liquefaction is taken into account. The developed code has been verified against the results of centrifuge experiment of VELACS No. 11. The numerical results are compared with the observed data consisting of seaward displacement of the wall, tilting and the generated pore water pressure in the soil. After validation, the influence of permeability and relative density of the soil on the residual deformation of the quay walls and on the generated pore water pressure are investigated. At the end, the effect of ground improvement on the seismic stability of the quay walls is investigated.

Effect of anelastic patchy saturated sand layers on the reflection and transmission responses of a periodically layered medium

ABSTRACTBased on analytic relations, we compute the reflection and transmission responses of a periodically layered medium with a stack of elastic shales and partially saturated sands. The sand layers are considered anelastic (using patchy saturation theory) or elastic (with effective velocity). Using the patchy saturation theory, we introduce a velocity dispersion due to mesoscale attenuation in the sand layer. This intrinsic anelasticity is creating frequency dependence, which is added to the one coming from the layering (macroscale). We choose several configurations of the periodically layered medium to enhance more or less the effect of anelasticity. The worst case to see the effect of intrinsic anelasticity is obtained with low dispersion in the sand layer, strong contrast between shales and sands, and a low value of the net‐to‐gross ratio (sand proportion divided by the sand + shale proportion), whereas the best case is constituted by high dispersion, weak contrast, and high net‐to‐gross ratio. We then compare the results to show which dispersion effect is dominating in reflection and transmission responses. In frequency domain, the influence of the intrinsic anelasticity is not negligible compared with the layering effect. Even if the main resonance patterns are the same, the resonance peaks for anelastic cases are shifted towards high frequencies and have a slightly lower amplitude than for elastic cases. These observations are more emphasized when we combine all effects and when the net‐to‐gross ratio increases, whereas the differences between anelastic and elastic results are less affected by the level of intrinsic dispersion and by the contrast between the layers. In the time domain, the amplitude of the responses is significantly lower when we consider intrinsic anelastic layers. Even if the phase response has the same features for elastic and anelastic cases, the anelastic model responses are clearly more attenuated than the elastic ones. We conclude that the frequency dependence due to the layering is not always dominating the responses. The frequency dependence coming from intrinsic visco‐elastic phenomena affects the amplitude of the responses in the frequency and time domains. Considering intrinsic attenuation and velocity dispersion of some layers should be analyzed while looking at seismic and log data in thin layered reservoirs.

Research on the Liquefaction Potential of the Yamansaz Region in Antalya, Turkey

This study is about identifying the liquefaction potential in Yamansaz Region (Antalya). The liquefaction potential is determined according to SPT-N values that are obtained from bore-hole data and laboratory experiment data. 45 boring wells were opened with each boring well depth of 15 m for the bore-hole data of the region. The study is conducted by using five liquefaction analyses which are: “Acceleration Threshold Criteria”, “Periodic Shear Stress Criteria”, “Liquefaction Index Criteria”, “Tokimatsu-Yoshimi Method” and “Seed-DeAlba Method”. Currently, these are the most used methods according to the literature. The liquefaction potential analysis is made in 16 boring wells in which SPT-N values are found to be low saturated sand, silty sand and clayey sand layers. According to the probability of an earthquake with magnitude of M=5.9, the region has a high potential of liquefaction that can be seen from the results obtained by using these five analysis techniques. In order to prevent the liquefaction in the region, methods such as stabilization with cement or lime, vibroflotation and etc. should be used before making any construction.

Iceberg ploughmarks illuminated by shallow gas in the central North Sea

Conventional 3D seismic data provides direct evidence for glacial influence during the early Pleistocene sedimentation in the Central North Sea. We identify iceberg ploughmarks as dim linear to curve-linear features in three early Pleistocene horizons that have high reflection amplitude compared to adjacent horizons. The anomalous horizons are interpreted to be reflections from thin sandy layers saturated with gas. The gas acts as a contrast liquid illuminating the thin sand layers. The reason for this is the difference in acoustic properties between water and gas saturated sand layers. The combination of thin bed effects and shallow gas makes the iceberg ploughmarks easily detectable as dim features in seismic reflection amplitude maps. Our interpretation is based on analysis of real seismic data, well logs and modeled seismic response. The methods we use include interpretation of horizons followed by extraction of reflection amplitudes, well log analysis, pre-stack amplitude versus offset analysis of high resolution 2D seismic data and time-lapse analysis of seismic. Seismic modeling is performed to study interactions between thin sand beds, shallow gas and iceberg ploughmarks. A new trapping mechanism for shallow gas is presented and seismic modeling of this trap strengthens our interpretation. The trap is created by iceberg ploughmarks in sandy layers that are covered by finer and less permeable sediments. For this area we find that conventional seismic interpretation is superior to the much used method of studying seismic time-slices for detection of iceberg ploughmarks, both with respect to time and detectability. This study shows that the interpreter should look for high amplitude horizons with amplitude variations laterally when trying to detect iceberg ploughmarks.

Bucket group effect of the composite multi-bucket structure

As a novel type of foundation in beach and shallow sea, the bucket structure is especially suitable for complex conditions such as soft clay ground and the worse types of sea environments. In this paper, the bearing capacity of a multi-bucket structure is studied by experiments with a single bucket and four-bucket foundation in a saturated sand layer. Based on the experimental data and numerical analysis results, the bearing capacity behavior and the bucket group effect are compared and analyzed. Furthermore, some influential factors, such as the soil type, the ratio of length to diameter L/D, the ratio of the bucket spacing to the bucket diameter S/D, and the bucket number are introduced and their effects on the multi-bucket structural capacity are investigated. The vertical static capacity adjustment factor is introduced to evaluate the bucket group effects of the multi-bucket foundation.

Glimpse into the design of MRS instrument

ABSTRACTThe Magnetic Resonance Sounding method (MRS) was developed in the former USSR in the late 1970s. Nowadays, available MRS instruments are more compact and reliable, and enormous progress has been made in electronics, computers and materials. Therefore, we can hope that it may be possible to increase the maximum depth of water detection and to improve the resolution of the method by using a larger current in the loop. Quite naturally, the questions arise: what are the practical limits of the MRS method and how much should be transmitting power to get the maximum depth of investigation? In this paper, we analyse the depth of groundwater detection and the vertical resolution of the MRS assuming different loops and different power levels of the current generator. The originality of our approach consists of a joint analysis of the maximum depth of investigation using accept able loop voltage and the modifications in the instrument design necessary for the improvements. We show that even under very favourable conditions it would be difficult to get significant improvement in the depth of investigation using currently available instruments. For example, under favourable noise conditions when rocks have low electrical conductivity and are non‐magnetic, a 20 m thick water saturated sand layer can be detected at a depth of about 325 m using an existing instrument (4 kV of the loop voltage) with a 400 × 400 m2 square loop. A 20% increase in the detection depth (390 m instead of 325 m) requires more powerful electronic equipment (16 kV instead of 4 kV) thus rendering the MRS system larger and heavier. However, using a 16 kV instrument allows us to increase the resolution depth by about 80% (from 120 m to 215 m). When rocks are electrically conductive, the screening of the MRS signal limits the depth of investigation and allows for only minor improvements even with a much more powerful current generator.

Experimental–numerical study of heat flow in deep low-enthalpy geothermal conditions

This paper presents an intensive experimental–numerical study of heat flow in a saturated porous domain. A temperature and a flow rate range compared to that existing in a typical deep low-enthalpy hydrothermal system is studied. Two main issues are examined: the effect of fluid density and viscosity on heat flow, and the significance and effect of thermal dispersion. Laboratory experiments on a saturated sand layer surrounded by two impermeable clay layers, subjected to different flow rates under cold and hot injection scenarios, and for both vertical and horizontal flow directions, are conducted. A temperature range between 20 °C and 60 °C is studied. The finite element method is utilized to analyze the experimental results. Backcalculations, comparing the numerical results to the experimental results, are conducted to quantify the magnitude of thermal dispersion. A constitutive model describing thermal dispersion in terms of fluid density, viscosity and pore geometry, taking into consideration different injection scenarios, is developed. This study demonstrates the importance of taking the variation of formation water density and viscosity with temperature into consideration in predicting the lifetime of deep low-enthalpy geothermal systems. It shows that if ignored, the lifetime of a system with hot injection will be overestimated, and that with cold injection, will be underestimated.

Experimental study on applicability of using time-domain reflectometry to detect NAPLs contaminated sands

Underground contamination by non-aqueous phase liquids (NAPLs) becomes increasingly serious. Rapid and reliable detection of contaminated zone and degree is the first step to site remediation. In this paper, diesel and fine sand are used as experiment materials to investigate the applicability of using time-domain reflectometry (TDR) to detect LNAPLs contamination. The major work includes: measurement of dielectric constant and electrical conductivity for the diesel-water-air-sand mixtures; measurement of reflection waveform and dielectric constant for specimens with a diesel contaminated layer being sandwiched in sand. The experimental results show the followings: A significant decrease in both dielectric constant and electrical conductivity is observed for the diesel-water-air-sand mixtures when diesel displaces the pore water, and the content of diesel can be calculated by the α model; insignificant change in dielectric properties is measured when diesel only displaces the pore gas; when the diesel contaminated sand is sandwiched between two saturated sand layers, the interfaces of the diesel contaminated layer can be identified by analyzing the reflection waveform; for field application, TDR method is valid for the case that LNAPLs seep into saturated sand layer, and the applicability of TDR method in vadose zone depends on the initial saturation of the sand layer. The findings obtained in this paper provide a guidance for the use of TDR for the field investigation of NAPLs contaminated site.

Experimental investigation of plastic demands in piles embedded in multi-layered liquefiable soils

Multi-layered soil profiles, where one or more layers consist of loose liquefiable material, most commonly require pile foundations extending beyond the liquefiable layer to competent material. Under seismic loads, if the loose layer liquefies, then large localized plastic demands may be generated in the piles. To study this behavior and provide detailed data to validate numerical models, a 1-g shaking table experiment was conducted considering a single reinforced concrete pile embedded in a three-layer soil system. The model pile of 25cm diameter was tested under increasing amplitude earthquake excitation in a sloped laminar soil box. The test specimen was designed at the lower bound of typical design to promote yielding, per ATC-32 (Applied Technology Council, 1996) [1]. The pile penetrated 7D (D=pile diameter) into a multi-layered soil configuration composed of a stiff uppermost crust overlying a saturated loose sand layer and a lower dense layer of sand. Plastic demands in the pile were characterized using curvature profiles coupled with back-calculation of the plastic hinge length and post-test physical observations. Results from this test quantify the post-yield behavior of the pile and serve as a complement to previously conducted centrifuge tests.

Liquefaction Response of Partially Saturated Sands. II: Empirical Model

Partial saturation in sands attributable to the presence of gas bubbles (not capillarity) can be encountered naturally in the field be- cause of the decomposition of organic matter, or it can be induced for liquefaction mitigation. An empirical model (RuPSS) was developed to predict the excess pore pressure ratio (ru) in partially saturated sands subjected to earthquake-induced shear strains. The model is based on experimental test results on partially saturated sands. Cyclic simple shear strain tests were performed on specimens prepared and tested in a special liquefaction box. Excess pore pressures were measured for a range of degrees of saturation 40%,S,90%, relative densities Dr 520267%, and cyclic shear strains g50:0120:2%. The test results demonstrated that partially saturated sands achieved a maximum excess pore pressure ratio (ru,max) when large enough cycles of shear strain were applied. The excess pore pressure ratio (ru) that partially saturated sand can achieve under a given earthquake-induced peak shear strain and the number of equivalent cycles of application can be significantly smaller than ru,max. Therefore, the empirical model was developed in two stages. In the first stage, ru,max was related to S, Dr, and shearstrain(g).In thesecondstage,amodelwasdevelopedrelatingru toru,max,shearstrainamplitude(g),effectivestress(s9),andearthquake magnitude(M).Thispaperpresentstheequationsthatdefinethepredictivemodelsforru,max andru.Throughtheseequations,plotsforru,max and ru are provided for ranges of soil and earthquake parameters for ease of use in engineering applications. To illustrate the implementation of the empirical model for predicting ru,max and ru, an example is presented in which a partially saturated sand layer experiencing a peak earthquake- induced shear strain was analyzed, and the pore pressure response of the sand was evaluated using both the predictive equations and the plots. DOI: 10.1061/(ASCE)GT.1943-5606.0000816. © 2013 American Society of Civil Engineers. CE Database subject headings: Soil liquefaction; Soil treatment; Saturated soils; Pore pressure; Empirical equations; Sand (soil type). Author keywords:Soil liquefaction; Soil treatment; Saturation; Pore pressure; Empirical equations; Induced partial saturation; Liquefaction mitigation; Empirical model; Soil model.