Matrix suction and diffusive transport in centrifuge models

1994 ◽  
Vol 31 (3) ◽  
pp. 357-363 ◽  
Author(s):  
R.J. Mitchell
Keyword(s):  
Soil Surface ◽  
Fine Sand ◽  
Lateral Spread ◽  
Diffusive Transport ◽  
Centrifuge Modelling ◽  
Deep Soil ◽  
Contaminant Fate ◽  
Centrifuge Models ◽  
Matrix Suction ◽  
Vadoze Zone

Centrifuge modelling of the lateral spread of a conservative solute in a partly saturated fine sand has been accomplished in a 3 m radius centrifuge at simulated gravitational accelerations of 25 and 50 g. The distributions of the contaminant after 2 months, 6 months, and 1 year of prototype time were found experimentally by dissection of models. The results support the contention that centrifuge modelling does correctly recreate prototype transport phenomena, including transport due to matrix suction, in partly saturated fine sand. For the conditions modelled, it was found that all of the contaminant introduced at the soil surface became immobilized, for at least 1 year, inthe upper 2–3 m of the 6 m deep soil profile. Key words : centrifuge modelling, contaminant fate, vadoze zone, matrix suction, diffusion.

Analytical Model to Predict Nonhomogeneous Soil Temperature Variation

1995 ◽  
Vol 117 (2) ◽  
pp. 100-107 ◽  
Author(s):  
M. Krarti ◽  
D. E. Claridge ◽  
J. F. Kreider
Keyword(s):  
Thermal Properties ◽  
Soil Temperature ◽  
Temperature Variation ◽  
Analytical Model ◽  
Soil Surface ◽  
Deep Soil ◽  
Soil Thermal Properties ◽  
Order Of Magnitude ◽  
Soil Surface Temperature ◽  
Annual Time

This paper presents an analytical model to predict the temperature variation within a multilayered soil. The soil surface temperature is assumed to have a sinusoidal time variation for both daily and annual time scales. The soil thermal properties in each layer are assumed to be uniform. The model is applied to two-layered, three-layered, and to nonhomogeneous soils. In case of two-layered soil, a detailed analysis of the thermal behavior of each layer is presented. It was found that as long as the order of magnitude of the thermal diffusivity of soil surface does not exceed three times that of deep soil; the soil temperature variation with depth can be predicted accurately by a simplified model that assumes that the soil has constant thermal properties.

scholarly journals Laboratory development of a vertically oriented penetrometer for shallow seabed characterization

2016 ◽  
Vol 53 (1) ◽  
pp. 93-102 ◽  
Author(s):  
Fauzan Sahdi ◽  
David J. White ◽  
Christophe Gaudin ◽  
Mark F. Randolph ◽  
Noel Boylan
Keyword(s):  
Soil Surface ◽  
Site Investigation ◽  
Soil Strength ◽  
Small Scale ◽  
Soil Parameters ◽  
Embedment Depth ◽  
Fine Grained ◽  
Centrifuge Models ◽  
Measured Resistance ◽  
And Performance

Current site investigation practice for offshore pipeline design relies on soil parameters gathered from boreholes or in situ test soundings to depths of 1–2 m below the mudline. At these depths, the fine-grained seabed is very soft and possesses low undrained strength, which can be difficult to measure. This paper describes a centrifuge test programme undertaken to evaluate the feasibility and performance of a novel penetrometer designed to assess the shallow strength of soft seabed over continuous horizontal profiles. This device is termed the vertically oriented penetrometer (VOP). Tests were performed on a normally consolidated kaolin sample, with the VOP translated horizontally at velocities ranging from 1 to 30 mm/s, after embedding the VOP at 30 and 45 mm depths. All tests involved many cycles of VOP forward and backward movement to assess its potential to derive the ratio of intact to fully remoulded strength. Strength determination is achieved by dragging the VOP at a specified embedment depth along the soil surface, and deriving the soil strength from the measured resistance as if the VOP were a laterally loaded pile. The VOP is shown to yield comparable strength measurements to that of a T-bar penetrometer. The VOP is a potentially valuable addition to the range of tools used to characterize soil strength, both in small-scale centrifuge models and, following practical development, potentially also in the field.

scholarly journals Time Function Model of Surface Subsidence Based on Inversion Analysis in Deep Soil Strata

2020 ◽  
Vol 2020 ◽  
pp. 1-6
Author(s):  
Jihuan Han ◽  
Chenchen Hu ◽  
Jiuqun Zou
Keyword(s):  
Soil Surface ◽  
Measured Data ◽  
Surface Subsidence ◽  
Time Function ◽  
Model Parameters ◽  
Deep Soil ◽  
Function Model ◽  
Composite Function ◽  
Inversion Analysis ◽  
Function Models

As a common geological disaster, surface subsidence caused by mining underground resources has always been a hot and difficult topic in the civil engineering field. Aimed at the shortcomings of existing time function models in predicting mining subsidence in deep soil strata, a more accurate and reasonable time function model, called the composite function model, was established based on an inverted analysis of measured data. The results showed that the composite function model could describe the whole subsidence process of a deep soil surface and agreed well with the measured data. The model parameters were calculated by specific formulas, which improved the reliability of the subsidence prediction results under different mining conditions. The new model provided important guiding significance for preventing subsidence geological disasters and determining the coal mining time under the buildings, the railways, and the water bodies in deep soil strata.

An experimental study of vertical infiltration into a structurally unstable swelling soil, with particular reference to the infiltration throttle

Soil Research ◽  
1973 ◽  
Vol 11 (2) ◽  
pp. 121 ◽  
Author(s):  
BJ Bridge ◽  
N Collis-George
Keyword(s):  
Soil Column ◽  
Soil Surface ◽  
Fine Sand ◽  
Coarse Sand ◽  
Sand Layer ◽  
Wetting Front ◽  
Sand Column ◽  
Swelling Soil ◽  
Potential Gradients ◽  
Moisture Potential

The infiltration phenomena associated with a structurally unstable swelling soil are compared with those of a two-layer stable system of a fine sand layer over coarse sand, the fine sand simulating a slaked layer at the soil surface. Water content and bulk density are measured using dual source gamma ray attenuation, pore water pressures by means of individual tensiometer-transducer systems, and soil temperatures by means of individual thermistor-bridge systems. Analysis of the sand column using well-established principles shows that after the wetting front has passed the texture boundary, infiltration is controlled by Kmax of the fine sand layer and the negative moisture potential in the coarse sand at the texture boundary. After the wetting front penetrates the column, the moisture potential at the texture boundary becomes steady and is unaffected by the development of a capillary fringe and outflow at the base of the column. The negative moisture potentials at the texture boundary give rise to potential gradients up to 6.0 in the simulated slaked layer, and an infiltration rate several times that of Kmax. The low flow rates caused by the fine sand layer give rise to an unstable wetting front in the coarse sand and severe 'fingering' occurs. In the swelling soil column, with aggregates of the same size as the coarse sand, the infiltration throttle occurs immediately below the visibly slaked layer and not at the ground surface. Potential gradients through the throttle reach a maximum of 5.9 similar to that in the layered sand column, but the infiltration behaviour of swelling soil differs from the latter in other respects. Infiltration into the former does not occur under isothermal conditions, a 'hot front' 3�C above ambient occurring 2-3 mm ahead of the wetting front, and infiltration does not reach a constant rate because of changes in the hydraulic properties of the throttle with time. Moisture profiles in the swelling soil column during infiltration show the various zones described by Bodman and Colman (1944) for non-swelling soils. An enlarged apparent transition zone extend to 12 cm below the soil surface. Other properties such as density, moisture content, and total potential suggest that much of this apparent transition zone is really part of a transmission zone made up of layers of soil which have different properties because of swelling.

Sensitivity of soil surface temperature in a force-restore equation to heat fluxes and deep soil temperature

1999 ◽  
Vol 19 (14) ◽  
pp. 1617-1632 ◽  
Author(s):  
Dragutin T. Mihailović ◽  
George Kallos ◽  
Ilija D. Arsenić ◽  
Branislava Lalić ◽  
Borivoj Rajković ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Soil Temperature ◽  
Soil Surface ◽  
Heat Fluxes ◽  
Deep Soil ◽  
Soil Surface Temperature

scholarly journals Experimental Researches Regarding Determination of Soil Cone Index in a Soil-Tyre Interaction Process

1970 ◽  
Vol 66 (1) ◽  
Author(s):  
Adrian MOLNAR ◽  
Victor ROŞ ◽  
Ioan DROCAŞ ◽  
Ovidiu RANTA ◽  
Sorin STĂNILĂ ◽  
...  
Keyword(s):  
Experimental Determination ◽  
Soil Compaction ◽  
Soil Surface ◽  
Interface Layer ◽  
Interaction Process ◽  
Deep Soil ◽  
Wheel Load ◽  
Initial Stress State ◽  
Cone Index

Soil compaction mainly occurs in occasions related with agricultural traffic, when the soil is subjected to various applied loads by different types of agricultural implements. Soil surface compaction and deep soil compaction occurs because of soil-tyre interaction process that will modify the initial stress state. This will alter the initial soil physical properties, so it is possible to evaluate the soil compaction by measuring their variation. This paper presents a tool and a method for experimental determination, in laboratory conditions, of soil cone index at soil-tyre interface layer and on soil profile, being focused only on data related with soil cone index influenced by wheel load and number of passes. The analysis of measured data showed that the analyzed method for experimental determination of soil cone index can be used also in field conditions, for studies related with spatial variation of soil cone index due to agricultural traffic.

Chemical and Physical Modification of the Rhizosphere

2000 ◽  
Author(s):  
Peter B. Tinker ◽  
Peter Nye
Keyword(s):  
Root Hairs ◽  
Soil Surface ◽  
Fine Sand ◽  
Root Surface ◽  
Root Penetration ◽  
Wheat Roots ◽  
Order Of Magnitude ◽  
Seminal Roots ◽  
Dry Soil ◽  
Living Organisms

The term ‘rhizosphere’ tends to mean different things to different people. In discussing how a root affects the soil, it is well to bear in mind the spread of the zone being exploited for a particular solute: if this is wide, there may be no point in emphasizing effects close to the root; but if it is narrow, predictions based on the behaviour of the bulk soil may be wide of the mark. In a moist loam after 10 days, a simple non-adsorbed solute moves about 1 cm, but a strongly adsorbed one will move about 1 mm. In a dry soil, the spread may be an order of magnitude less. The modifications to the soil in the rhizosphere may be physical, chemical or microbiological. In this chapter, we discuss essentially non-living modifications, and in chapter 8 the modifications that involve living organisms and their effects. Roots tend to follow pores and channels that are not much less, and are often larger, in diameter than their own. If the channels are larger, the roots are not randomly arranged in the void (Kooistra et al. 1992), but tend to be held against a soil surface by surface tension, and to follow the channel geotropically on the down-side. If the channels are smaller, good contact is assured, but the roots do not grow freely unless some soil is displaced as the root advances. For example, in winter wheat, Low (1972) cites minimum pore sizes of 390–450 μm for primary seminal roots, 320–370 μm for primary laterals, 300–350 μm for secondary laterals, and 8–12 μm for root hairs, though some figures seem large. Whiteley & Dexter (1984) and Dexter (1986a, b, c) have studied the mechanics of root penetration in detail (section 9.3.5). It may compact and reorient the soil at the root surface. Greacen et al. (1968) found that wheat roots penetrating a uniform fine sand increased the density only from 1.4 to 1.5 close to the root; and a pea radicle, a comparatively large root, raised the density of a loam from 1.5 to 1.55.

scholarly journals Quarternary Sediment Characteristics of Floodplain area: Study Case at Kampar River, Rumbio Area and Surroundings, Riau Province

2018 ◽  
Vol 3 (1) ◽  
pp. 63
Author(s):  
Yuniarti Yuskar ◽  
Dewandra Bagus Eka Putra ◽  
Muhammad Revanda
Keyword(s):  
River System ◽  
Fine Sand ◽  
Sediment Deposition ◽  
Sediment Supply ◽  
Lateral Spread ◽  
Stream Channel ◽  
Terrestrial Organic Matter ◽  
Depositional Facies ◽  
Meandering River ◽  
Sand Bars

The study area is located in some floodplains of meandering river environment along the Kampar River, Rumbio. Typical morphology of meandering river that found in this area can be classified as stream channel, floodplain, abandoned channel, and sand bars deposit. Meandering river system carries sediment supply by suspended and bed - load (mixed load) in conjunction with low energy into a particular characteristic on sediment deposition. This study aims to determine the characteristics of the sediments, changes in vertical and lateral spread of sediment deposition on the floodplain environment. This study conducted by field survey using a hand auger of 1.5m - 4m depth and trenching which is a layer that has been exposed of 1-2 meters depth. Further analysis had been carried out using granulometri method and core data analysis to determine the characteristics and depositional facies. Sediment deposit that formed along the Kampar River is the result of the main channel migration of Kampar River. The characteristic of quaternary sediment facies is coarse to gravelly sand on the bottom followed by fine to very fine sand with pattern fining upwards and silt to clay and abundant terrestrial organic matter at the uppermost layer. Depositional facies are determined based on the characteristics of sediment facies which can be grouped into a stream channel, oblique accretion deposits, sand bars and overbank deposits.

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