Sandy Soil Layer Research Articles

Site Effects and Peak Ground Accelerations Observed in Guadalajara, Mexico, for the 9 October 1995 Mw 8 Colima-Jalisco, Earthquake

On 3 June 1932, an M s 8.2 shallow thrust subduction earthquake struck the Colima–Jalisco (CJ) region of Mexico at an epicentral distance of ∼250 km from Guadalajara, the second largest town in Mexico. The return period of these CJ earthquakes has been estimated from 77 to 126 years, which suggests the next is likely to occur between 2009 and 2058. As a step toward estimating the seismic hazard posed by potential M s 8.2+ events on Guadalajara, we present a study consisting of the following: (1) the analysis of the strong ground motions recorded at Guadalajara on 11 free‐field accelerographs for the CJ 9 October 1995 M w 8 earthquake; (2) the analysis of the site effects in Guadalajara observed for this earthquake; and (3) the estimation of the spatial distribution of peak ground acceleration (PGA) in Guadalajara for this event. We propose, validate, and apply a recurrent neural network (RNN) technique to the recorded PGA. Important site effects were identified (using the horizontal‐to‐vertical and H/Hrocksite techniques) on Guadalajara’s sandy soil layers with thicknesses h >20 m to the basaltic rock basement. The estimated PGAs in Guadalajara for the CJ 1995 earthquake varied from ∼2 to ∼27 cm/s2 for soil layers with h ≤5 m and h >50 m, respectively. We expect the hybrid technique to obtain broadband synthetics (Chavez et al. , 2011) and the proposed RNN methodology can be used to estimate Guadalajara’s seismic hazard for M w 8+ CJ scenario earthquakes. Online Material: Figures of Fourier amplitude spectra, H/V and H/H spectral ratios, and signal‐to‐noise spectral ratios.

Sand grain mineralogy and morphology under forest and grassland/arable fields in Eastern Hungary

Related to ongoing (re)forestation in the Great Hungarian Plain the short-term influence of changing land cover was studied on the grains of skeletal sandy soils. In three sampling areas with forest and grassy/arable control plots, the 0.1–0.2 mm grain size fraction of samples taken every 20 cm from the 0–100 cm sandy soil layer (totalling 22,509 grains) were separated and described with optical mineralogical microscope. In order to distinguish sand grains of forest-covered and control areas (grassland/arable land), the results of mineralogical and morphological observations were compared. It was revealed that the amount of feldspar grains is 8–9 times less than the amount of the quartz ones. The increase in the quartz/feldspar (q/fp) ratio is tied to the “consumption” of feldspars: the intense consumption of potassium by trees. Under the forest-covered fields, the number of in-situ crushed grains increased. Grains with etch pits are frequent in samples from the grasslands (except in Hajdúsámson). In samples of forest-covered areas a greatly increased number of brown grains with limonite and/or humus films were observed. The gained results can be useful in proving earlier land use in forested fields.

Full-Wave Calibration of Time- and Frequency-Domain Ground-Penetrating Radar in Far-Field Conditions

Full-wave modeling of ground-penetrating radar (GPR) data using Green's functions for wave propagation in planar layered media and antenna characteristic global reflection and transmission functions for describing far-field antenna effects, including antenna-medium interactions, has shown a great potential for nondestructive characterization of soils and materials. The accuracy of the retrieved parameters in the GPR data inversion depends on the accuracy of the GPR external calibration. In this research we studied the stability and the repeatability of two different GPR systems, namely, frequency- and time-domain systems. A combination of a vector network analyzer and 800-5200 MHz horn antenna was used as a frequency-domain GPR (FD-GPR) whereas a GSSI GPR system using a 900 MHz bowtie antenna was used as a time-domain GPR (TD-GPR). Both GPR systems including their antennas were calibrated several times using measurements with the antennas at different heights over a perfect electric conductor (PEC) in the laboratory as well as over a water layer. In addition, measurements were performed over a thin water layer and a relatively thick sandy soil layer as validating medium. The results showed that the FD-GPR is relatively stable while the TD-GPR presents a significant drift which can be accounted for using corrections based on the air direct-coupling waves (free-space measurements). Water- and PEC-based calibrations provided very similar results for the GPR calibration functions. Inversions for the water layer and the sandy soil layer provided reliable results and showed a high degree of the repeatability for both radar systems. The error on the calibration based on inaccurate antenna heights over PEC showed the significant errors on the inversion results for the directive antenna (horn antenna) but less error for the bowtie antenna. This analysis demonstrated the general validity of the proposed far-field radar modeling approach, not only with respect to frequency and time domain radars but as well with respect to the calibrating medium.

洪積砂質土層での液状化判定方法の一考察

洪積砂質土層での液状化判定方法の一考察

Root system size of alfalfa varieties under different plant densities

The field experiment was established from pre-grown alfalfa sprouts in 2008. In 2009 and 2010, the harvest was carried out. The yield and the root size system (RSS) were evaluated in the total of five cuts. Two localities of diverse soil and weather conditions were selected. Žabčice is a dry location with a highly permeable sandy soil layer, but at the same time, with a considerable fluctuation of the underground water level; Troubsko, on the other hand, represented a location with a higher content of clay in soil suitable for growing alfalfa. The trial was established in two types of plant spacing – 25 × 25 cm (16 plants per m2) and 50 × 50 cm (4 plants per m2). Two alfalfa varieties were used – Hodonínka (an old variety) and Oslava (a new variety). The following factors were evaluated by statistical means: location, variety, plant spacing, and cut number. The effect of location on the above ground phytomass and the RSS value proved highly statistically decisive. The higher average values of above ground phytomass as well as RSS were achieved on the Troubsko location where the above ground phytomass was 19.57 t.ha−1 and RSS was 2.71 nanofarad (nF). The impact of the variety was highly statistically significant only in respect to RSS. The effect of variety on the alfalfa above ground phytomass was not proven. The higher average RSS values were reached by the Hodonínka variety (2.59 nF). The effect of the plant spacing on both the above ground phytomass and the RSS values was highly statistically significant. The higher average above ground phytomass was achieved when the 25 × 25 cm plant spacing was employed (18.64 t.ha−1). As for the RSS value, the case was exactly opposite – the higher average value was reached when the plant spacing was 50 × 50 cm (2.99 nF). The impact of the cut number on both the above ground phytomass and the RSS was highly statistically significant. The highest average above ground phytomass and root system size were measured in the third cut. The above ground phytomass was 30.36 t.ha‑1 and RSS was 3.86 nF.

Microbial secreted exopolysaccharides affect the hydrological behavior of induced biological soil crusts in desert sandy soils

The effect of the presence of microbial secreted exopolysaccharides (EPSs) on the hydraulic conductivity, water capture and moisture retaining capabilities of Induced Biological Soil Crusts (IBSCs) was investigated. In the experimental sites under study, located in Hobq Desert (China), the formation of these IBSCs was induced three to eight years before the tests by a massive inoculation in sandy soils of mixed cultures of Microcoleus vaginatus and Scytonema javanicum. In all the sites under study, the IBSCs showed to be well consolidated and differently developed in relation with their age. All the crust samples showed a significant content of EPSs, which contributed to the structure of the crusts. The hydraulic conductivity (HC) was significantly lower in the IBSCs than in the underlying bare soil and a statistically significant negative correlation between HC and the amount of high molecular weight (>100 kDa; HMW) and of low molecular weight (<100 kDa; LMW) carbohydrates in IBSCs was found. The capability of the crusts to retain moisture, coupled with the preservation of their structural integrity, was found to be positively correlated with the amount of total and of HMW carbohydrates in IBSCs. The uptake of atmospheric humidity showed a positive correlation with the amount of LMW carbohydrates in destructured IBSCs. In conclusion, this study showed the crucial role played by the EPSs of IBSCs in trapping and retaining humidity in sandy soils, thus increasing the water availability in the first layers of sandy soils and reducing water infiltration, protecting the soil from erosion.

Shaking Table Test to Underground Structures in Layered Foundation

A three-story underground structure shaking table test had been carried on to study the earthquake damage mechanism of underground structure in layered foundation. The test model was similar to typical subway station according to a certain similarity ratio, and the soils were disturbed sandy soil and silty clay dug from the site of Harbin subway. Shaking table tests to this typical model in silty clay and alternating layers of clay and sand were performed to reveal the effect of different layered soils. Results show that the sandy soil layer can reduce the damage of the soil and underground structure, the damage of underground structure is mainly controlled by displacement of the surrounding soil, and the response of shallow buried underground structure is larger than deep buried.

Advanced Numerical Analysis of Jack-Up Spudcan Penetration in Layered Sandy Soil

Quasi-static numerical model of jack-up spudcan penetration in layered sandy soil was presented in this paper, based on explicit procedure. Three different methods, such as Lagrangian analysis, Lagrangian analysis with distortion control and Lagrangian-Eulerian analysis, were used to control soil negative element volumes or other excessive distortion. The results showed that, reasonable and stable numerical results could be solved by Lagrangian-Eulerian analysis. The magnitude of plastic strain, however, decreases at first and then increases to the maximum.

Investigation of Static Laterally Loaded Pile in Layered Sandy Soil

Investigation of the static lateral load resistance of pile on layered sandy soil was made by laboratory model test on single pile. The experiment was carried out with variable diameter and variable embedded length of pile on sandy soil. In this study, model pile was single pile which satisfies the Meyerhof’s Relative Stiffness limit of pile for flexible pile. Single pile embedded length, L=0.46m, 0.609m, 0.762m for pile diameter, d=0.013m, 0.019m, 0.026m, respectively. And for surcharge condition embedded length of single pile, L=0.609m and surcharge of pressure, P=3369.55Kg/m3, P=6739.1 Kg/m3 and P=13478.20Kg/m3 for each diameter and for saturated condition of pile diameter, d=0.013m. These experiments were conducted with local sand of Rajshahi region and domar sand; available in Bangladesh. Lateral static loads were applied in the single by a static lateral load set up arrangement. Due to the static lateral load the pile was deflected. The load-displacement response, ultimate resistance of pile has been qualitatively and quantitatively investigated in the experiment. The lateral resistance of pile obtains by experiment and the ultimate lateral load resistances obtained by analytical methods were compared. The load displacement curves are similar and non-linear. Lateral failure at a pile head displacement from 8 to 10, 7 to 9 and 6 to 8mm for single pile of d= 0.013m, 0.019m and 0.026m, respectively. In the case of saturated condition of sand a pile head displacement 15mm for single of d=0.013m. It observed that the failure load was the point at which the curve exhibits a pick or maintains continuous displacement increase with no further increase in lateral resistance. DOI: http://dx.doi.org/10.3329/jsf.v8i1-2.14630 J. Sci. Foundation, 8(1&amp;2): 83-88, June-December 2010

Off- and on-ground GPR techniques for field-scale soil moisture mapping

Precise measurement of shallow volumetric soil water content (VSWC) is essential in different research fields, including agriculture, hydrology and meteorology. In this research three different approaches were applied for mapping the shallow VSWC of a bare soil at the field-scale, namely, (1) the direct ground wave (DGW) method using on-ground ground-penetrating radar (GPR), (2) the surface reflection coefficient (SRC) method also using on-ground GPR, and (3) the surface reflection inversion using off-ground GPR. Measurements were conducted in an agricultural field in both relatively dry and wet conditions. Soil sampling was performed at different depths (5, 10, 20, 30, 40cm) for determining the reference VSWC. The on-ground GPR was setup using two transmitting (Tx) and receiving (Rx) 400MHz bowtie antennas with Tx and Rx offsets of 0.16 and 1.26m, respectively, thereby setting up a multi-offset system. A vector network analyzer combined with a 0.2–2GHz TEM-horn antenna located at 1.1m above the ground was used as off-ground GPR. GPR measurements were performed following more than 10 transects in the entire field and positioning was performed using a dGPS. In addition, on-ground GPR measurements were conducted in the laboratory over a sandy soil layer including 10 different VSWC, ranging 0.02–0.18cm3·cm−3, in order to examine the SRC method for the on-ground GPR configurations. The Topp's model (1980) was used in order to transform the relative dielectric permittivity of the soil to the VSWC. Laboratory results showed that SRC method can be confidently used also for the on-ground GPR configurations when the air direct-coupling wave is subtracted from all signals. For the field data, the validation graphs using the ground-truths of the shallowest layer showed relatively reliable VSWC-maps with the RMSE values of 0.042, 0.044, and 0.059 in terms of VSWC for the SRC, DGW, and full-wave methods, respectively. In addition, the existence of a very shallow bedrock made a confusion on the detection of the DGW from the GPR data in the dry condition, but had no effect in the wet condition.

Centrifuge simulation of LNAPL transportation in sand deposits with containment under flow and no-flow conditions

Light nonaqueous phase liquid (LNAPL) contamination of subsoil is a serious problem affecting human health and disturbing the environment. This paper describes centrifuge tests of LNAPL migration in a sandy soil layer that were focused on a soil-cement barrier as a containment to protect the groundwater from contamination. Two centrifuge tests were performed in this study for the following two scenarios: groundwater flow and no groundwater flow conditions. Liquid paraffin oil was used to represent LNAPL, and it was infiltrated into the partially saturated sand deposit. The centrifuge tests were performed at 30g, and pore pressure sensors and camera recordings were used to evaluate the model behaviour. The results show that groundwater flow accelerates LNAPL migration in sandy soil. In addition, LNAPL was found to migrate below the groundwater level, and the soil-cement barrier was found to serve effectively for containment.

Alrum – Brandtomter i en vestjysk byhøj fra ældre jernalder

Alrum – Brandtomter i en vestjysk byhøj fra ældre jernalder

Soil properties after 10 years of organic versus conventional management in two greenhouses in Almeria (SE Spain)

Field experiments were conducted to evaluate the effect of a long-term (10 years) organic management on a greenhouse soil compared with the same soil under intensive conventional management. Soils of each greenhouse have an artificial sequence of layers: 0–10 cm depth of sand mulch with a dominant particle size of 0.5 mm–2.0 mm, and between 10 and 40 cm depth of loamy sandy soil layer with moderate infiltration as crop substrate. During the last 10 years, organic greenhouse received manure equivalent up to 170 kg N ha−1 year−1 (over 5600 kg ha−1 year−1 of manure of 3% N) mixed with crop substrate at 10 cm depth, while conventionally managed greenhouse received no organic amendments during this time. Water and nutrients were supplied to both greenhouses by drip irrigation, as required for crops. Crop rotation was similar in both greenhouses. An experimental plot (90 m2) was established in each greenhouse and nine soil samples were taken near the drippers. Organic management diminished pH and bulk density and, as a consequence, improved infiltration, but reduced the water retention capacity. Total organic carbon, total nitrogen and cation exchange capacity were augmented by comparison with conventional management.

Characteristics of Water and Salt Transport in Layered Soils

Characteristics of water and salt transport in layered soils with the loess soil layer overlapping different particle size sandy soil layer, was investigated in two dimensions soil chamber. The results show that, finger flow occurs when the wetting front enters into the low layer sandy soil, and the accumulative infiltration is greater for coarser particle size sandy soil than that for finer particle size one. The behavior of water movement and salt transport are disagree since salt content in soil profile has a significant difference for two treatments and water content is almost same. The further analysis explains this phenomenon is mainly caused by adsorption of the finer sandy soil to Na+. In additional, Cl- is easier to movement in pathway of the finger flow than that of Na+ whether the soil texture was same or not.

Influence of Rock Socketing on the Lateral Response of Single Pile

This paper examines the influence of rock socket lengths on the lateral response of piles embedded in homogeneous sandy soil overlying rock. A 3-D finite element based numerical analysis has been used to investigate the performance of piles due to socketing into the rock. Parametric studies have been carried out for understanding the behaviour of piles in a continuum consisting of a sandy soil layer overlying a rock mass layer. The numerical results are discussed in terms of the lateral load–deflection relationships and bending moments along the length of the pile with reference to pile head fixity conditions and rock socket lengths, which are of prime interest to designers. The limiting rock socket lengths for achieving the maximum beneficial effect is found to be equal to the width of the pile for both free and fixed head piles.

Soil profile internal drainage for a central pivot fertigated coffee crop

Coffee cultivation via central-pivot fertigation can lead to fertilizer losses by soil profile internal drainage when water application is excessive and soils have low water retention and cation adsorption capacities. This study analyses the deep water losses from the top 1 m sandy soil layer of east Bahia, Brazil, cultivated with coffee at a high technology level (central-pivot fertigation), using above normal N fertilizer rates. The deep drainage (Q) estimation is made through the application of a climatologic water balance (CWB) program having as input direct measures of irrigation and rainfall, climatological data from weather stations, and measured soil water retention characteristics. The aim of the study is to contribute to the understanding of the hydric regime of coffee crops managed by central-pivot irrigation, analyzing three scenarios (Sc): i) rainfall only, ii) rainfall and irrigation full year, and iii) rainfall and irrigation dry season only. Annual Q values for the 2008/2009 agricultural year were: Sc i = 811.5 mm; Sc ii = 1010.5 mm; and Sc iii = 873.1 mm, so that the irrigation interruption in the wet season reduced Q by 15.7%, without the appearance of water deficit periods. Results show that the use of the CWB program is a convenient tool for the evaluation of Q under the cited conditions.

Coupling Effect between Single Key Strata and the Overburden Thick Sandy Soil Layer

Through the simulation model test, coupling effect between single key strata and t overburden thick sandy soil layer is studied, failure character of thick sandy soil layer is obtained. Meanwhile, load transmitting law on the key strata(key block) is found. This discovery will make progress on dynamic roof structure theory.

Effects of System Compliance on Liquefaction Behavior of Thin Sandy Layer in Undrained Cyclic Triaxial Tests

ABSTRACT In a case history of dip slope failure caused by the 2004 Niigata-ken Chuetsu Earthquake, it has been reported that the slope contained a thin sandy soil layer. The layer may have liquefied if it had been saturated at the time of the earthquake. Undrained cyclic triaxial tests comprise one of the available experimental approaches for evaluating the liquefaction behavior of such thin sandy soil layers. In this study, a series of undrained cyclic triaxial tests was performed on specimens containing an artificial sand layer in order to investigate the effects of system compliance that are possibly induced by partial drainage caused by the changes in volume of the filter paper used to saturate the sand layer and the local drainage at the interface among the specimen, the top cap and pedestal, and the rubber membrane. The observed liquefaction behavior depended on the thickness of the sand layer under otherwise similar conditions, suggesting the significant effect of system compliance. By conducting special tests, while correcting the partial drainage, it was possible to reduce its effect on the liquefaction behavior. Cylindrical specimens with a top cap and pedestal, all having the same diameter, exhibited a smaller effect from partial drainage than prismatic specimens with an oversized top cap and pedestal.

Analysis of the mechanisms of slope failures triggered by the 2007 Chuetsu Oki earthquake

The 2007 Chuetsu Oki earthquake (MJMA = 6.6) triggered more than one hundred slope failures in the northwest part of Niigata prefecture, Japan. A reconnaissance survey conducted by the authors revealed that although most of the failures were only a few meters deep, they still caused significant damage to roads, railways, and houses. It was also found that a vast number of shallow slides were concentrated along the coastal line of the Japan Sea, while only few, but relatively larger failures occurred in a mountainous part of the study area, which is located in a considerable distance from the earthquake’s epicenter. This paper summarizes the reconnaissance observations, describes the geologic characteristics of the area covered by landslides, provides characterization of major types of the landslides, and examines the causes and mechanisms of typical failures. In addition, this paper seeks to investigate the mechanism of the Ohzumi landslide, the largest slide triggered by the Chuetsu Oki earthquake. For this purpose, a comprehensive analysis that included field investigation and laboratory testing of soils samples was performed. Results of field investigation suggested that the failure plane of the Ohzumi landslide formed in a saturated layer of sandy soil near a boundary with bedrock. Data from undrained cyclic loading triaxial compression tests indicated that the sandy material was highly susceptible to generation of high excess pore-water pressures during earthquake loading. On the basis of the obtained results and the outcome of seismic response and slope stability analyses, the authors posited an explanation on the mechanism of the Ohzumi landslide.

Spatial Variation of Moisture Content in Shallow Aeolian Sandy Soil in the Southern Marginal Zone of the Gurbantonggut Desert

In May 2008,the vegetation,terrain and landforms were investigated at a plot of 200 m x 50 m in a typical region of longitudinal sand dunes in the southern marginal zone of the Gurbantonggut Desert.At the plot 180 quadrats were selected for the observation,measurement and soil sampling.These soil samples were sampled from the surface layer(0～10 cm)and shallow layer(10～30 cm),and their moisture content values were measured. Under the support of geostatistical software,such as GS~+ and geostatistical model in ArcGis,this paper analyzes the spatial varying pattern of soil moisture content at the different positions of two longitudinal sand dunes in the study area.The results show that the semi-variance functional values of soil moisture content in the two layers can be well fitted as an exponential model.The variation ranges of surface layer and shallow layer of aeolian sandy soil are 37.8 m and 21.3 m,and the ratios of partial sill and sill[C/(C_0+C)]are 75.1%and 75.6%,respectively.These reveal that there is a high spatial autocorrelation in soil moisture between the surface layer and the shallow layer of aeolian sandy soil,and the spatial variation of the soil moisture content comes mainly from a structural difference. The results can objectively reflect the spatial structure pattern of soil moisture in the plot.The figure of Kriging interpolation shows that soil moisture content is correspondently increased with the height increase of terrain.The analyzed results show that the values of soil moisture content are in an order of crestwindward slopeleeward slopeinter-dune land in the surface layer(0～10 cm)of aeolian sandy soil,and an order of windward slopecrestleeward slopeinter-dune land in the shallow layer(1030 cm).