Effects Of Burial Depth Research Articles

Structural vibrations of buried land mines

Buried landmines exhibit complex structural vibrations, which are dependent on interaction between soil and mines as well as on their respective properties. This paper presents experimental and theoretical studies of multimodal vibrations of buried mines and discusses the effects of burial depth and soil properties on dynamics of the soil-mine system. The two-dimensional model of the soil-mine system that accounts for soil-coupled mine’s multiple vibration modes and spatial distribution of vibrations over the soil surface is introduced. The model was tested using experiments with the plastic mine simulant. The study reveals that the soil shear stiffness is one of the key governing parameters determining the resonance vibration frequency and the amplitude of the soil-mine system. Burial depth, soil moisture, and consolidation are among factors leading to the increase of the soil shear stiffness, therefore effectively influencing modal vibrations of buried mines.

Lateral Pipe–Soil Interaction in Sand with Reference to Scale Effect

This paper investigates the pipe.soil interaction for pipes buried in cohesionless soil when subjected to lateral ground movement. A review and reappraisal of the literature is conducted to identify some inconsistencies and shortcomings of previous studies. The effects of model scale, stress level (via burial depth), burial depth ratio, and soil properties are systematically addressed through finite element analyses. The study concludes that the effects of pipe size and burial depth must be taken into account to properly estimate the maximum pipe.soil interaction forces induced by lateral ground movement. A unique equation considering scale and the effect of burial depth is proposed to determine the maximum pipe-soil interaction forces at various burial depth ratios.

Landmine vibration modes

Recent experimental and theoretical studies in the field of seismo-acoustic landmine detection proved high potential of this technique. Investigations have also demonstrated that acoustic detection and discrimination of landmines is a complex problem dependent upon interaction between soil and buried mines and their respective properties. Vibration characteristics of a mines casing play a critical role in this problem. Our recent tests, for the first time, revealed the multi-modal vibrations of mines. It was observed that the resonance frequencies of the soil/mine system depend on the burial depth and soil conditions. The present study provides analysis of this phenomenon both experimentally and though physical modeling. The experimental investigations were focused on the effects of burial depth and soil moisture content on vibration response measured on the soil surface above the buried mine. The modeling efforts were based on the electro-mechanical analogy approach where each vibration mode was represented as an oscillator with its own effective parameters. The validity of this consideration was confirmed through comparison against conventional modal analysis approach. The study demonstrated good agreement between the developed model and experimental results.

Fluid in mineral interfaces—molecular simulations of structure and diffusion

We study the effect of burial depth on thermodynamics and transport properties of fluids confined between mineral surfaces. The solvation curve and diffusion coefficients of fluid films confined between mineral surfaces have been obtained for different states of stress and temperature using Grand Canonical Monte Carlo and molecular dynamics simulations. Our results indicate that the mass transport coefficient (film thickness times diffusion coefficient) of the thin films of fluids trapped at grain contacts decrease by a factor 40 from 1 km to 3 km and 10 km. This effect has strong implications on the rates at which mechano‐chemical processes of deformation (e.g. pressure solution) occur in the upper crust.

Effects of dung presence, dung amount and secondary dispersal by dung beetles on the fate of Micropholis guyanensis (Sapotaceae) seeds in Central Amazonia

The study of seed fate is crucial for understanding fruit-frugivore interactions. One factor that can greatly influence the fate of seeds dispersed through mammal defecation, is the dung that accompanies the seeds. Dung attracts dung beetles and rodents; the former eat and bury dung, the latter feed on seeds. In this study the fate of Micropholis guyanensis subsp. guyanensis seeds surrounded by no dung and by 5, 10 and 25 g of howler monkey dung was followed until seedling establishment. The depths at which dung beetles bury the seeds were measured, and the effect of burial depth on seedling emergence was determined. Although initial seed fates differed among treatments, the same percentage of seedlings established from seeds without faecal material, and from seeds with 5, 10 and 25 g of dung. However, a significantly higher proportion of seedlings established from buried seeds when compared to seeds that remained on the surface. The percentage of seedlings establishing in a controlled germination experiment decreased significantly with increasing burial depth. The effect of dung beetle activity should be taken into consideration when assessing the role that mammal endozoochory plays on seed dispersal ecology of tropical plants. These results provide further evidence for the emerging realization that the study of secondary seed dispersal and post-dispersal events is crucial for a more complete understanding of plant regeneration.

Managing the weed seedbank

Weed control is essential in field vegetables but there has been a continual decline in the range of herbicides available. Growers aim to keep crops weed‐free throughout to maintain yield, but a short weed‐free period or even a single weeding can achieve the same result. In order to predict the optimum weeding period in advance, a realistic estimate is needed of the size, timing and duration of a flush of weed emergence in the crop. The weed seeds in the soil are the primary source of future weed populations, and this seedbank provides a unique resource for predictive management purposes. A preliminary model has been developed that combines information on the effect of burial depth of weed seeds on seedling emergence with a simulation of the incorporation and movement of seeds in soil following the use of different cultivation implements. The objective is to develop a suite of models which will provide a decision support system for weed control in field vegetables.

Pullout behavior of suction anchors in soft marine clays

In the field of ocean engineering, a beginning has been made in the use of large‐sized suction anchors for safe anchoring of large compliant structures. Suction anchors derive most of their uplift resistance from passive suction developed during the pullout movement. This article describes a set of laboratory tests on model suction anchors of three different embedment ratios to estimate the pullout behavior of suction anchors in soft clays typical of Indian marine clays. Tests were conducted on model anchors installed in soil beds prepared at four different consistencies in a test tank. This study shows the influence of soil consistency and embedment ratio (L/D) on the pullout behavior of suction anchors and on the variation of suction pressure at the top of the soil plug. The test results reveal that the behavior of suction anchors is much better than the behavior of open‐ended anchors from the considerations of both capacity and deformation. The consistent development of suction inside the anchor top confirms the plug formation and significant breakout resistance in the form of suction‐induced reversed end bearing. The results are further analyzed in terms of suction breakout factors. Further, the effect of burial depth of suction anchor on pullout behavior is shown.

Longevity of Yellow Starthistle (Centaurea solstitialis) Achenes in Soil

Yellow starthistle achenes were placed in 80-mesh nylon packets, buried in the field at depths of 2.5, 5, and 15 cm, and retrieved over 10 yr. No effects of burial depth on longevity were detected. Viability decreased faster for plumeless achenes than for plumed achenes. Average longevity of plumeless and plumed achenes was 6 and 10 yr, respectively.

Behavior of Jointed Ductile Iron Pipelines

Experimental data on the axial, bending and torsional behavior of ductile cast iron pipes with rubber gasket joints is presented. Analytical expressions are provided which predict the resistance mechanisms and behavior of the joints. The bending mechanism is found to be quite different from the axial and torsional mechanism. By repeating the tests in a specially designed soil box, the effects of burial depths are determined. A joint stiffness matrix including axial, bending and torsional effects is provided. The slip behavior of the joint changes the stiffness values, however this occurence may be dealt with by using an appropriate flag system. To minimize axial compressional stresses and interlocking bending stresses at the joint, a minor geometrical change in the joint needs to be made. Joints with larger lip lengths provide more flexibility when subjected to axial compression or joint bending rotations.

Geothermal and other effects on amino acid racemization in selected Deep-Sea Drilling Project cores

Kinetic parameters for the epimerization of isoleucine in multispecific foraminiferal asemblages were used to establish the effects of burial depth and the geothermal gradient on the extent of reaction. It was observed that with a little as thirty meters of burial in a normal thermal regime there were differences between the extent of epimerization measured and that which would have been predicted for thermal equilibrium with bottom water temperatures. As would be expected, these differences are greatest when the heat flow (the geothermal gradient) and/or the sedimentation rates are highest. These effects were observed in most of the DSDP samples studied, and have been used to estimate the average heat flux since the time of sample deposition. Occasional anomalous effects were observed which could not be related to past or present heat flux. These were determined to be due to such geologic occurrences as slumping and reworking or to recent sample contamination. Other problems emerged related to bottom water temperatures including changes over geologic time which are unknown and could not be deduced. Thus, the presence of epimerization anomalies in DSDP cores as noted above limits the effectiveness of amino acid geochronology in such cores, unless these anomalies can be recognized as ab initio.

Thawing of Permafrost Beneath a Buried Pipe

Abstract The rate of thaw beneath the center of a hot pipe buried in permafrost was calculated by the quasi-steady approximate method. The solution assumes a purely conductive heat transfer model. The heat loss at the surface was included for the case of a pipe buried at a finite depth. Functions are presented which allow the thaw Tate below the pipe and the heat transfer from the pipe to be calculated for any pipe radius, burial depth, temperature of the pipe surface, as well as initial temperature and thermal properties of the surrounding permafrost. The method allows a quick estimate to be made of the effect of burial depth, temperature and soil thermal properties on the phase change beneath a pipe. The same details can also be applied to the case of freezing around a buried pipe. Introduction THE PROBLEM OF THAWING beneath a hot pipe buried in permafrost, or in permafrost regions, has been of considerable interest. Unfortunately, the nonlinear nature of the problem precludes exact solutions when the geometry of the system is curvilinear. However, the exact solution for the semi-infinite region, known as the Neumann problem(1) is available and the details of this solution demonstrate the validity of the quasi-steady, or Stefan(2), approximate method. This idea relies on the fact that the rate of movement of the phase change interface is slow enough that the heat transfer for each region is essentially steady-state at any instant of time. This method was extended by Khakimov(3) to the case of a cylinder embedded in an infinite medium, where the concept was used of a finite volume around the cylinder in which the temperature is disturbed. Gupta'" extended the method to the analogous case of the sphere. There are numerous numerical solutions of the problem, such as those of Lachenbruch(5), but these methods are lengthy when applied to two-dimensional problems and are not convenient for quick estimates. Theory Consider the case of thawing of a medium initially frozen at temperature To. A hot cylinder with a surface temperature Ta is inserted into the medium at zero time. The thermal effect will extend, at any time, to a finite distance (a), i.e., the initial temperature of the medium will be unchanged at a location sufficiently far from the hot cylinder. This distance is denoted by the radius (a) and it can be assumed that the ratio α = a/R is a constant, using α = 4.5, as did Khakimov. Using the quasi-steady assumption and letting 0 = T ? To, the temperature for each region (see Fig. 1) will be the solution of the one dimensional conduction equation: (Equation Available In Full Paper) The energy required to thaw region 1 and increase the temperature of regions 1 and 2 is the sum of the latent plus the sensible heats and can be written as: