Soil Bed Research Articles

Research of conditions of supporting underground pipeline and loads on protective coating

During the construction and operation of underground pipelines, there is a need to develop projects for the engineering protection of insulation coatings from the mechanical effects of coarse soil. The task is most relevant with significant variability of the laying conditions along the length of the route. In particular, the difficult laying conditions include the passage of the route in the areas of distribution of rocky, gravelly and permafrost soils. The appropriateness of applying the methods of engineering protection of the insulation coating from mechanical stress should be justified both economically and in terms of technical and operational indicators. Therefore, the task of analyzing the conditions of support of the underground pipeline and the study of the created forces in the supporting part of the pipeline is very relevant and characterized by insufficient knowledge. The article analyzes the effect of bedding soil and backfill on the amount of force arising in the protective coating of the supporting part of the pipeline in the presence of unevenness of the base and its particle size distribution. The results of modeling the contact problem using models of a discrete (granular) medium at the base of the pipeline are presented. The wall thickness of the pipes affects the change in created force in the supporting part of the pipeline (for pipes are 1 420 mm the maximum difference is 22 %). In the presence of unevenness of the base, the force in the supporting part can increase by 3–5 times.

Direct and indirect effects of pine silviculture on the larval occupancy and breeding of declining amphibian species

Abstract Plantation silviculture is increasing globally and is particularly intensive in temperate coniferous forests, where densely planting trees requires practices common to non‐conifer systems that can alter forest floor microhabitat, and potentially threaten amphibian persistence. Most declining amphibian species depend on specific forest microhabitats as terrestrial refugia, but amphibian extirpation associated with tree harvest alone appears unlikely, suggesting that impacts of planting forests on groundcover might better predict recent declines in amphibian occupancy. We repeatedly sampled larval presence or absence of 10 amphibian species native to temperate coniferous forest in the Southeastern United States for one year at 62 isolated wetlands, located in either naturally regenerating or planted forest (plantation). We assessed three direct ways that planted forests might reduce amphibian breeding site occupancy by: (a) increasing conifer densities, (b) decreasing groundcover, and (c) an indirect pathway, whereby increased tree densities at plantations might reduce groundcover and thus amphibian site occupancy. After controlling for wetland traits and accounting for differences in detection, breeding site occupancy for 8/10 amphibian species was dependent upon whether forests were planted surrounding wetlands (within 300 m). Herbaceous groundcover, not canopy, most commonly influenced occupancy and increased occupancy for declining surface active or fossorial amphibians. Path analyses showed that, by directly and indirectly reducing groundcover (via conifer densities), plantations had significantly lower occupancy of two declining surface active or fossorial frog species, whereas two common aquatic frog species were tolerant to planting conifers. Among declining species, salamanders showed a greater reduction in occupancy than anurans, likely because of greater vulnerability to the drier forest floor conditions of plantation than naturally regenerating forests. Synthesis and applications. Direct negative impacts of coniferous plantation on amphibians can be addressed by limiting groundcover and soil impacts, including switching from high intensity practices, such as mechanical chopping vegetation or bedding soil, to lower intensity site preparation treatments that are less likely to significantly disturb groundcover. Indirect negative effects of dense canopy cover at planted forests could be lowered by periodically thinning canopies prior to final harvest, thus increasing intact forest groundcover and the conservation of both common and declining amphibians.

Modelling the transport and adsorption dynamics of arsenic in a soil bed filter

Arsenic is among the most hazardous contaminants present in drinking water. Recent increase in agricultural growth and fertiliser use in India and Bangladesh has led to the release of naturally occurring arsenic from the rocks, creating a major public health issue. A novel technology has been developed using naturally abundant laterite soil to filter arsenic, providing potable water to more than 5000 people. To upscale this technology and realise its full potential, a comprehensive understanding of the dependence of filter life on operating regime (flow rate, arsenic concentration and filter size) is essential. We present a mathematical model that characterises arsenic removal, circumventing the need for time-consuming experiments. The model incorporates inter- and intra-particle mass transport within the filter medium. The resulting model enables prediction of a filter lifetime in a specified role, such as on a domestic or community scale, and should assist in future filter deployment and maintenance.

EM 담체를 충전한 하천 모의실험의 수처리 효율 산정

Experiments were carried out to investigate the effect of EM application on stream purification in simulated river filled with EM media. The river bed soil of artificial stream had made with 11.9 % of gravel, 74.2 % of sand, 8.7 % of silt and 5.2 % of clay. And their the sorting was 2.17, the skewness was 0.47, and the kurtosis was 2.05. Algae, black fungus, green algae, and red tubificid were shown with the macroscopic observation. From a result of water quality analysis for effluents, the temperature was 19.4 ± 6 ℃, pH was 6.3 ~ 8.5, DO was 6.3 ~ 8.5 mg/L, EC was 0.14 ~ 0.25 μs/cm, ORP was 94~158 mV and turbidity was in the ranged of 1.0 ~ 3.8 NTU. The simultaneous packing of EM media and river bed soil(RS-2), the removal efficiencies of COD, NH₄ ⁺-N and PO₄ ^3--P were accomplished to 80.0 %, 95.3 %, 67.1 % at 7 L/min water cycling flow, 80.5 %, 98.1 %, 88.5 %, at 13 L/min flow, 83.3 %, 98.2 %, 90.4 % at 40 L/min flow, respectively.

MODELS FOR DETERMINING MAXIMUM DEGREE FILLING CHANNELS OF CIRCULAR SECTION SHAPE

Objectives The task was to obtain a model for determining the maximum possible degree of filling the circular section channels in the earthen channel based on the condition of ensuring the stability of slopes and the minimum volume of excavation during their construction, as well as finding the optimum degree of filling fortified channels of a closed profile corresponding to maximum throughput.Method In work analytical methods of differential calculus and the solution of implicit equations are used.Result The experience of domestic and foreign researchers was taken into account to solve the set tasks, select research methods and criteria for optimizing channel parameters. Two cases of circular-shaped channels are considered: 1) in the earth channel, 2) reinforced with a closed transverse profile. For the case of a hydraulically most advantageous circular channel in the earthchannel channel, equating the first derivative of the equation of a circle with the reciprocal of the allowable embedding coefficient of the slopes obtained an analytical solution for determining the maximum degree of filling from the slope stability condition, which was not dependent on hydraulic flow elements. In the case of non-cohesive soils that form the channel, the circular channel can be filled to a depth not exceeding 20 percent of the channel radius. At the same time, the average flow rate should remain in the range from non-venting to non-blurring. In order to be able to determine the flow rate, analytical expressions are given for finding hydraulic flow elements in a circular channel. When determining the volume of excavation for the construction of the channel, the excess of the channel edge above the maximum water level in the channel was taken into account. For the case of a fortified channel of a closed transverse profile, by taking the derivatives from the Chezy formula, we obtained the optimal values of flow rate and average velocity.Conclusion A fortified closed circular profile channel has a maximum capacity with a relative degree of filling of 0.938, and the maximum average velocity of a fluid in a pressureless channel is achieved with a degree of filling of 0.815. To determine the maximum permissible relative degree of filling in the case of a circular section channel in the earthen channel, analytical dependences were obtained, before using which, according to the reference literature, it is necessary to take the value of the slope coefficient for this type of channel bed soil.

Performance Assessment of Screw Piles Embedded in Soft Clay

Screw piles are widely used in a variety engineering applications supplying stability against compression, overturning moment, uplift tension, and horizontal loads. Screw pile is a famous solution for support light structures, roads and rail signs which have relatively low-capacity foundation. In this study, the behavior of circular (10) mm solid screw pile models embedded in a bed of soft clay soil covering a layer of sandy soil has been studied. The 200 mm thick sand layer was compacted in a steel container with a diameter of 300 mm into four sublayers. The sandy soil layer was compacted at a relative density of 70%. The 300 mm thick soft clay soil bed with Cu (30) kPa was compacted in six sub-layers on the sandy bottom layer. Model tests are carried out with screw piles with a length of 300 mm, 350 mm and 400 mm and a helix diameter of 30 mm. Also, single and double helix and different S/Dh ratio were used for these piles and a comparative study between screw piles and ordinary piles (without helices) is accomplished. This study revealed that introducing screw pile of double helix increases its bearing capacity in soft clay soil by up to a (4-8) % as compared to a single helix screw pile. The results showed that the behavior of screw pile essentially depends on the geometric properties of the pile. According to the achievements, compressive load capacity of screw piles depends on embedded length, spacing ratio (S/Dh) and number of helical plates.

Pore Water Pressure Response of Fully Saturated Soil Beds during Earthquake–Tsunami Multi‐Hazards

AbstractSoil liquefaction causes significant damage to coastal infrastructure and buildings worldwide. Strong earthquake shaking can cause soil liquefaction in fully saturated sand deposits. Also, tsunamis can induce liquefaction, as well as enhanced sediment transport and scour, in coastal areas. To understand soil liquefaction potential during an earthquake–tsunami multi‐hazard, we develop a numerical model to predict the multi‐hazard induced excess pore water pressures. We calibrate and verify the numerical model by comparing results with laboratory experiments. Then, we perform numerical experiments using a recorded earthquake motion and hypothetical tsunami wave heights. The numerical experiments show that beach sand liquefies during earthquake loading. The sand then resediments during the quiescent period and the tsunami runup stage. Finally, during rapid tsunami drawdown, liquefaction can occur again, and liquefaction potential during tsunami drawdown primarily depends on the soil’s hydraulic conductivity, as well as the duration of the quiescent period. The results emphasize the need for predictions of earthquake–tsunami loading, as well as measurements of soil properties in coastal areas.

Application of the conductive method in the engineering geology: Ruczaj district in Krak\xf3w, Poland, as a case study

The Ruczaj district in Kraków is the potential building area of high flat blocks for inhabitants. This area is built of the gypsum basement covered by the soil and impermeable clay beds with several meters of thickness. The flat blocks must be set on the textured gypsum layer. In the result of the rainfall and static pressure of the blocks, the water with SO42− increases up to the groundwater level, become the great threat for the flat blocks. The water creates specific hydrogeological conditions occurring in the zone of the building’s foundations. To eliminate the mentioned threat, we should determine precisely the thickness of the soil and impermeable clay as well as the depth of the gypsum basement. Based on the electromagnetic parameters of the geological formations, the Ground Conductivity Meter and DC resistivity methods were used to solve the mentioned problems.

An experimental investigation into the behavior of sand reinforced by tubular braided structures

This study introduces the tubular braided structure as a new geosynthetic material for sand reinforcement. The performance of a tubular braid under the influence of similar soil–reinforcement interaction mechanisms has been investigated to emphasize the effect of the reinforcement form on the performance of the reinforced soil composite. For this purpose, three series of interaction element tests including direct shear tests, pull-out tests, and soil stress control tests were conducted on the unreinforced and reinforced sand. Finally, the overall performance of the reinforced foundation bed with the planar and tubular reinforcing textile (with similar materials, properties, texture, and areal density) was evaluated through a series of standard plate load tests. The results indicated that the performance of the sand-braid composite was better compared to the similar typical planar reinforcement, except for the case of pull-out test. Tubular braid resulted in the enhanced shear strength of the reinforced soil composites, mobilization of the excess compressive stress in the enclosed soil inside the tubular braids, reduction in the vertical stress level of the footing model transferred down through the soil bed, the increase of the average bearing capacity of the footing model, and a significant reduction in the footing settlement.

Simulating Tsunami Inundation and Soil Response in a Large Centrifuge

Tsunamis are rare, extreme events and cause significant damage to coastal infrastructure, which is often exacerbated by soil instability surrounding the structures. Simulating tsunamis in a laboratory setting is important to further understand soil instability induced by tsunami inundation processes. Laboratory simulations are difficult because the scale of such processes is very large, hence dynamic similitude cannot be achieved for small-scale models in traditional water-wave-tank facilities. The ability to control the body force in a centrifuge environment considerably reduces the mismatch in dynamic similitude. We review dynamic similitudes under a centrifuge condition for a fluid domain and a soil domain. A novel centrifuge apparatus specifically designed for exploring the physics of a tsunami-like flow on a soil bed is used to perform experiments. The present 1:40 model represents the equivalent geometric scale of a prototype soil field of 9.6 m deep, 21 m long, and 14.6 m wide. A laboratory facility capable of creating such conditions under the normal gravitational condition does not exist. With the use of a centrifuge, we are now able to simulate and measure tsunami-like loading with sufficiently high water pressure and flow velocities. The pressures and flow velocities in the model are identical to those of the prototype yielding realistic conditions of flow-soil interaction.

Integrated modelling of potential recharge in small recharge ponds

Integrated models that simultaneously simulate potential recharge and time delay for wetting front to reach water table are necessary for comprehensive and coordinated planning of managed aquifer recharge. Most of the existing models do not simultaneously simulate the potential recharge, length of advancement of wetting front, and time delay for wetting front to reach water table except the few numerical models, which are data intensive, high initial software and data setup cost, spatial and temporal discretisation depended accuracy, and time-consuming. This paper presents an integrated potential recharge simulation (IPRS) and time delay for wetting front to reach water table (TDWF) models for simultaneously simulating the potential recharge and time delay for wetting front to reach water table under time-variant inflows and outflows, respectively. The models have been derived by integrating the modified Green-Ampt model for variable water depth into the water balance equation of recharge pond. The numerical calculations of the IPRS and TDWF models are performed by the computer program written in Fortran-95. The performance comparison of the IPRS and TDWF models with HYDRUS-1D model for a hypothetical recharge pond over variety of soils showed its ability and comparability with the HYDRUS model. The models have also been successfully demonstrated for a recharge pond in a watershed in a semi-arid region of India. The IPRS model was found to be sensitive to the changes in inflow and saturated hydraulic conductivity of the bed soil of the recharge pond. The derived models will be helpful in simultaneous simulating the potential groundwater recharge and time delay to reach water table and optimum design and evaluating the effectiveness of recharge ponds and/or other surface artificial groundwater recharging facilities of any shape and size in the field.

Growth of lettuce cultivars in beds covered with differing materials

In commercial lettuce growing, the intensive cultivation of the soil results in an increase in weed populations, making it difficult to fully exploit the area and increasing production costs. Under such
 circumstances, the use of soil covers can minimize this problem. Consequently, the objective of this study was to evaluate the effects of different materials as soil covers on the agronomic performance of three lettuce cultivars. The experiment was arranged in randomized blocks, with treatments set in a subdivided plot scheme. Five types of soil cover (plots) were tested: no cover, black plastic, double white faced plastic, straw mulching and kraft paper and three Lettuce cultivars (subplots): loose-crested leaf group, iceberg lettuce group, with four replicates. Number of leaves per plant, stem length and diameter, head diameter, mass of fresh and total dry matter, fresh matter mass of leaves and stem were evaluated. For the Lisa and Americana lettuce groups, bed soil cover materials were more efficient when compared to the uncovered beds. For economic and environmental reasons, kraft paper is recommended as a bedding cover material for these cultivars. Variation in growth occurred between the lettuce cultivars, independently of the use of bedding cover. This
 occurred in the sequence: loose leaf > iceberg lettuce> loose-crested leaf group.

Interference of proposed footing with an existing footing resting on non-linearly elastic dense and loose cohesionless soil bed

The study was performed using finite element analysis to find interference effect of a footing, which is proposed to be constructed in close proximity of an existing footing resting on a semi-infinite non-linearly elastic dense and loose cohesionless soil bed obeying the widely used hyperbolic constitutive model. The interfering footings are of identical size (B). Varying the clear spacing (S) between footings, its effect on the performance of proposed footing in terms of pressure-settlement behaviour, bearing pressure/capacity and settlement aspect at permissible limit has been studied and compared with an isolated/existing footing and with interfering footings loaded simultaneously. Further, the effect of proposed footing on the performance of existing footing has been explored. The results highlight the interference has a significant effect on the bearing pressure/capacity and settlement aspect of the proposed footing and the behaviour is asymmetrical in comparison with the footings loaded simultaneously. The bearing pressure/capacity and settlement at the permissible limit are at their peak at a certain S/B ratio. For footings on dense sand, the interference effect is significant on bearing pressure/capacity aspect, whereas on settlement aspect for footings on loose sand. The overall effect is significant for S/B ≤ 6.0 for footings on dense cohesionless soil bed.

Badania modelowe skuteczności oczyszczania ścieków w piasku średnim z warstwą wspomagającą z hydro-antracytu

The model investigations of sewage purification were carried out in a medium sand bed with an assisting hydro-anthracite layer with thickness of 0.10 and 0.20 m. It has been observed that the effectiveness of sewage purification related to basic qualitative parameters (total suspended solids – TSS, BOD5, COD, total nitrogen, total phosphorus) is in accordance with the Polish standards on sewage disposal into grounds and surface water. It has been stated that the medium sand soil bed with the 0.20-meter thick assisting hydro-anthracite layer shows higher effectiveness of sewage purification than the 0.10 m thick assisting layer. This application in the medium sand soil bed increased the removal efficiency regarding TSS by 3.1%, total nitrogen by 29.4%, ammonia nitrogen by 1.2% and total phosphorus by 23.0%, and reduction efficiency regarding BOD5 by 1.5% and COD by 11.3% with relation to the 0.10-meter thick assisting hydro-anthracite layer (all percentages – in average). The investigations confirm that the hydro-anthracite with the granulation of 1.8–2.5 mm can be used to assist in removal of nitrogen and phosphorus compounds from sewages

Damping characteristics of full-scale grouped helical piles in dense sands subjected to small and large shaking events

A full-scale pile testing program was implemented using the large outdoor shake table at the University of California – San Diego. Nine steel helical piles with varying geometry were embedded in dense sand and tested individually and in 2×2 groups, comparing fixed and pinned pile head connections. The test piles were subjected to shake motions ranging from pulses and white noise to replicated earthquakes. Strain gauges attached to the exterior pile walls and accelerometers placed on the pile caps and within the soil provided data for analyzing the behavior of these piles. Foundation damping (herein soil–pile system) is a substantial parameter in seismic design of the foundation–structure. Therefore, the damping characteristics of the soil bed along with the combined soil–pile system consisting of single and grouped helical piles are discussed based on the experimental pulse, white noise, and shake excitations. Several methods, including logarithmic decrement, half-power bandwidth, and energy (equivalent) methods, were implemented to estimate the damping ratio over a range of strains. Based on the experimental data gathered from this study, the suitability and accuracy of different computational methods to determine damping ratio as well as the effect of type and location of instrumentation on the calculated damping ratio were evaluated.

Vertical Pullout Behaviour of a Torpedo Anchor Vertically in Stiff-Over-Soft Cohesive Soil Bed

This paper reports the results from a large deformation finite element (LDFE) model to provide insights into the vertical pullout behaviors of torpedo anchors in stiff-over-soft soil beds. 10 sets of numerical data were obtained by varying the top layer thickness, soil shear strength of the stiff-over-soft soil bed, tip embedment depth ratio, and pullout speed. The tip embedment depth ratio of the torpedo anchor (the ratio of the embedment depth at anchor tip to the anchor shaft length) varied from 1.48 to 2.91. Soil flow characteristic was discovered by the finite element analysis. The observation of soil flow characteristics provided deep insight with the interaction between the torpedo anchor and its surrounding soil.

Bedding of Wetland Soil: Effects of Bed Height and Termite Activity on Wood Decomposition

Core Ideas Wood stake decomposition is a function of both microbial and termite attack in raised beds in the US southeast. Microbial decay was greater in single and double beds than in half beds and unbedded soil. Mass loss was similar for both aspen (Populus tremuloides Michx.) and loblolly pine (Pinus taeda L.). Termites were active only on aspen stakes in single and double beds, where they increased mass loss 20‐30%. As wood stakes decomposed, soil microsite variability of mass loss increased. Microorganisms and termites are the primary wood decay agents in forests of the southeastern United States, whose activity can be affected by forest management practices. Bedding establishes raised planting beds on poorly‐drained soils, but little is known about the effect of bedding or soil bed height on wood decomposition. Therefore, a four height bedding study was conducted on a wetland soil in eastern South Carolina: flat (no bedding), half (7.5 cm), single (20 cm), and double (30 cm) above the original soil surface. Aspen (Populus tremuloides Michx.) and loblolly pine (Pinus taeda L.) wood stakes were inserted to 30‐cm soil depth, sampled over 23 mo, and decomposition (mass loss) by soil microorganisms and termites assessed. Microbial decay of both aspen and pine stakes increased as bed height increased, approaching 50% mass loss in double beds at the end of the study. Termites were not present in the flat (unbedded) soil, only damaged <1% of stakes in half beds, but were very active in single and double beds. Termites damaged or consumed 43% of aspen stakes in the double beds, which increased aspen mass loss by 30%. In contrast, termites attacked only 11% of pine stakes in double beds, and had little impact on mass loss. Stake decomposition was highest at the 5‐cm soil depth and was affected by soil microsite variability among soil bed heights. Soil bedding increased wood decomposition by both soil microorganisms and termites, and their impact on soil organic matter content and productivity deserves more attention.

Effects of Early Structural Changes of Engineered Soils on Green Roof and Bioretention Performance

Engineered soils play an important role in urban hydrology e.g. in the functioning of green roofs and storm water bioretention beds. Water infiltration, colloid transport and heat transport are affected by changes in pore system geometry particularly due to development of macropores and clogging by particles. The rate of pedogenesis is often faster than in natural soils due to higher loads of particles as well as by extreme water regimes. In the presented project we assess the temporal changes of hydraulic properties of engineered soils in typical bioretention beds and green roofs by conducting field scale experiments. The aim is to elucidate changes in hydraulic properties by studying the structural changes of soils at the microscale by invasive and noninvasive methods. The outcomes of the research will lead to improved design and management procedures for green roofs and bioretention beds.

Effect of geocell-reinforced sand base on bearing capacity of twin circular footings

The presence of a rigid layer underlying a soil bed layer supporting twin footings affects the footing bearing capacity and settlement. In this study, the bearing capacity and settlement of twin large-scale circular footings on unreinforced and geocell-reinforced sand layers with various thicknesses are investigated. The role of layer thickness, distance between two adjacent footings, and footing diameter indicates that the rigid base substantially influences the footing bearing pressure, settlement and tilt. The results show that the maximum bearing capacity is achieved when two footings are in contact and the rigid base is at shallow depth. The influence of the footing interference on settlement and tilting of closely spaced footings at a given load decreases with decreasing depth of rigid base and reinforcing the sand with geocells. This is observed for rigid bases located at less than about 2B, where B is the footing diameter.

Impact of soil puddling intensity on the root system architecture of rice (Oryza sativa L.) seedlings

Puddling of rice paddies is undertaken to create a soft soil bed for easy transplanting of rice seedlings, to control weeds and reduce water and nutrient leaching. There is a drive for less intense puddling because of its physical disturbance of soil, energy inputs and labour requirements, which may produce different soil physical conditions for root growth. The objective of this study was to investigate the influence of puddling intensity on soil structure and the subsequent impact on the growth of rice seedling roots. Three treatments with different puddling intensities were established: (1) No puddling; (2) Low and (3) High intensity puddling. The rice genotype, Nipponbare was grown in soil columns for 18 days. Soil bulk density, aggregate size distribution and three-dimensional (3D) macropore structure were measured. Two-dimensional root traits were determined by WinRhizo and 3D root traits were determined by X-ray Computed Tomography (CT). Our results show the percentage of large macroaggregates (> 2 mm) decreased by 69.6% (P < 0.05) for low intensity puddling and by 95.7% (P < 0.05) for high intensity puddling compared with that of no puddling. The macroporosity (> 0.03 mm) of no puddling was 2.3 times greater than low intensity puddling and 3.5 times greater than high intensity puddling. The total root lengths of no and low intensity puddling were 1.56–1.86 times greater than that of high intensity puddling. Large roots, including radicle and crown roots, were the same length regardless of puddling intensity. Our study demonstrates that intensive puddling can degrade soil structure, which consequently limits rice root growth.