Loose Fills Research Articles

Underground Morphological Detection of Ground Fissures in Collapsible Loess Area Based on Three-Dimensional Laser Scanning Technology

Underground coal mining inevitably causes ground fissures, especially permanent cracks that cannot be closed at the boundary of the working face. Studying the underground three-dimensional morphology of the permanent cracks allows one to accurately constrain the formation and development of the ground fissures. This information will contribute to reducing mine disasters and is also a prerequisites to avoid environmental pollution. We selected the Zhangjiamao coal mine (China), which is situated in a collapsible loess area, as a case study for deciphering the formation of permanent cracks. After injecting gypsum slurry into the mine, a three-dimensional model of the ground fissures is obtained by three-dimensional (3D) laser scanner technology that records the 3D underground morphology. Integrating the geological context of a collapsible loess area, the characteristics and main processes of the ground fissure development are constrained: (1) The width of the ground fissure decreases to 0 with increasing depth and is strongly affected by the soil composition. (2) Along the vertical extension direction, the ground fissures are generally inclined to the inner-side of the working face, but the direction remains uncertain at different depths. (3) The transverse propagation direction of the ground fissure becomes more complex with increasing depth. (4) Under the influence of soil texture and water, loose soil fills the bottom of the ground fissure, thus affecting the underground 3D morphology.

Stability Analysis of Dry Sandy Slopes Adjacent toDynamic Compaction Process

Dynamic compaction is a useful economic method for improving different soil types, especially loose sandy fills. However, the method has been rarely used in the vicinity of slopes due to stability concerns. In this research, dynamic compaction method adjacent to slope edge was numerically simulated using 2D plain-strain finite element models. Stability of slope models under different compaction energies and slope geometries at the same initial static factor of safety (FS) was investigated considering different stability criteria. These criteria include peak particle velocity (PPV) or peak particle displacement (PPD) on the slope, rate of change in plastic volumetric strains, yield stress ratio on the induced slip surface and the ratio of crater depths in flat and sloped models. Safe compaction distances from slope heel were calculated for different criteria and it was concluded that PPV criterion yields the most conservative distances but PPD criterion almost shows the smallest safe distances. Based on comparison of different criteria, it was concluded that combination of yield stress ratio and rate of plastic volumetric strain achieves the most acceptable safe compaction distance values for consideration in slope stability analyses.

Experimental study on stiffness properties of non-engineered clay and granular fills

Non-engineered fills are produced by human activity or natural occurrences. They can be placed without any controlled compaction effort or processing operation. In order to determine the stiffness properties of non-engineered fills, laboratory experimental studies have been performed and case history records are compiled. Some laboratory tests were conducted on poorly graded sand and fragmentary cohesive materials from a non-engineered fill made during canal excavation in the northern area of Iran. One-dimensional compression behavior of the fill materials was assessed and the deduced constrained moduli were compared with the results of other studies. Evaluation of case histories indicates that settlement caused from water infiltration into spoil fills may lead to excessive settlements. Moreover, in massive cohesive fills, hydro-compression settlement is significant. However, in loose granular fills, settlements due to dynamic loading and liquefaction can be substantial. Investigations revealed that, except for the cases with saturated cohesive materials, stiffness properties seemed to be a major aspect in comparison to the strength characteristics in geotechnical practice.

Densification of Land Reclamation Sands by Deep Vibratory Compaction Techniques

AbstractLoose granular sand deposits formed during the land reclamation process are vulnerable to liquefaction upon imparting seismic forces. These loose granular sand fills could encounter bearing failures or compress beyond tolerable limits under static and dynamic loads. To eliminate such failures, loose granular soils require densification to enhance their engineering properties. Deep compaction is the only means to improve these thick deposits of loose sand fill in many foreshore land reclamation projects. Muller resonance compaction (MRC) and vibroflotation are deep vibratory compaction techniques, which are suitable to densify thick layers of loose granular fills. This paper describes the applications of deep compaction vibratory techniques in a mega-land reclamation project in the Republic of Singapore where the efficacy of densification was verified by cone penetration tests (CPT) undertaken in a pilot test area. In the MRC technique, high vibrating energies are used, which results in the whole m...

Influence of palaeokarst morphology on the formation of ice-pushed ridges: a case study from Rejowiec, eastern Poland

This article describes the well-exposed landform/sediment assemblage of a Pliocene palaeouvala and Pleistocene (Saalian) ice-pushed ridge in a large quarry in Upper Cretaceous marls near Rejowiec, eastern Poland. The site provides a rare opportunity to study the development of glacial depositional and deformational processes on morphologically and structurally variable bedrock. The internal structures of both chronostratigraphic units which comprise this assemblage provide evidence of two principal stages of deformation associated with an ice advance on a karstified foreland, each stage preceded by stabilization of the ice mass. The first deformational stage was characterized by the development of imbricate structures in outwash sediments (the initial ice-pushed ridge) and listric faults at the contact between the bedrock and palaeouvala fills (caused by an increasing ice load). Shallow subglacial folding of the proximal fan deposits, and a listric thrust which limited the extent of the ice-pushed ridge under development occurred in the second deformational stage. The data assembled indicate that the formation of push moraines (in a general sense) during ice-sheet advance is controlled by the substratum undulations. Closed depressions with loose fills in the foreland of advancing ice sheets can control the deformational style, geometry and extent (both lateral and vertical) of the push moraines.

Is device closure for direct access valved stent implantation safe?

Despite the progress made in the development of valved stents for trans-apical valve replacement, a reliable closure of the access orifice remains a major issue. The present study was designed to evaluate if device closure of the ventricular wall is safe. Transventricular access for pulmonary valve replacement was simulated with a 26F sheath and the resulting orifice was closed with an Amplatzer Muscular VSD Occluder (AMuscVSDO) in chronic sheep experiments (body weight 45-48 kg). Mean procedure time, blood loss, and standard hemo-dynamics were recorded. The animals were sacrificed electively and the histopathological changes in and around AMuscVSDO in the right ventricular wall were systematically studied by semi-quantitative analysis of collagenisation, inflammatory response and 'resorptive' process. Mean procedure time was 31+/-10.7 min, blood loss was 22.5+/-8.7 ml, heart rate was 123+/-22.6 bits/min before and 128+/-28.7 bits/min after, mean arterial blood pressure was 88+/-16.7 mm Hg before and 82.6+/-18.3 mm Hg after the procedure. Mean survival was 5.3 weeks. The collagen and scar formation studies revealed three different periods: (1) initial fibrosis (0-3 weeks); (2) so-called 'capsulation' (3-9 weeks after the implantation of the Occluder); and (3) final remodelling and differentiation (9 weeks). The fabric inside the Occluder played the role of a collagenisation promoter, active from the 3rd week till it vanishes. Inflammation plays a role as a temporary reaction (0-3 weeks) during the healing process, with no signs of any active, focal or circumscribed, myocardial damage. (1) The closure of the free ventricular wall perforation with AMuscVSDO is safe due to the scar tissue resulting from the healing process around and in the device. (2) The myocardial healing around and inside an implanted AMuscVSDO represents two processes: extensive fibrosis ensues around metallic wires with the progression towards the inside of the myocardium, whereas inside AMuscVSDO the loose connective tissue fills the myocardial lesion. During cicatrisation, the fabric elements of AMuscVSDO act as the ground for collagen formation and fibroblast proliferation. (3) The cicatrisation processes after ventricular AMuscVSDO implantation show remodelling, with rearrangement of collagen fibres architecture and distribution.

CHARACTERISTICS OF GROUND MOTION IN LIQUEFIED DEPOSITS DURING EARTHQUAKES

Two well-documented case histories on liquefaction of reclaimed fills during the 1995 Kobe earthquake are discussed in this paper. The two sites, Vertical Array site (VA-site) and Packing House site (PH-site) are in proximity to each other and have practically identical stratification with an 18 m thick fill layer overlying an alluvial clay layer. At the VA-site, no ground improvement had been implemented and the reclaimed deposit of gravelly sand is loose with a low SPT blow count of about 5 to 10. The fill layer at the PH-site, on the other hand, had been densified prior to the earthquake by means of the rod compaction technique resulting in an increase in the SPT resistance to approximately 20 to 30 blow counts. To investigate the effects of ground treatment and evaluate the difference in the ground response between the densified fills and undensified loose fills during the Kobe earthquake, detailed studies were conducted for the two sites including field investigations, laboratory tests and effective stress analyses. It was found that both the extent of liquefaction and ground deformation were significantly different at the two sites. The undensified loose fills at the VA-site completely liquefied below the water table resulting in maximum shear strains of about 4% and settlement of the ground of about 25-30 cm. On the other hand, the analyses reveal that only the deep part of the densified fills at the PH-site liquefied where the maximum shear strains are estimated to have reached 2% and settlement of the ground was about 8 cm. Thus, the densification of the fills was found to be effective in preventing liquefaction from developing at shallow depths of the deposit and in limiting the overall deformation and settlement of the ground.

Laboratory study of soil–nail interaction in loose, completely decomposed granite

The technique of soil nailing is seldom used in stabilizing loose fill slopes because there is a lack of understanding of the interaction behaviour of nails in loose fills. A large-scale laboratory apparatus has been built to study the soil–nail interaction in loose fill materials. Pullout tests were performed in a displacement-rate-controlled manner on steel bars embedded in loose, completely decomposed granitic soils. The load–displacement curves have distinct peak values followed by a sharp decrease in the pullout force. The test results also show that the normal stress acting on the nail changes because of the volume-change tendency and arching effect of the soil being sheared around the nail. The post-peak decrease in the pullout force is mainly due to the reduction in the normal stress caused by the arching effect of soil around the nail. The conventional method of analysis tends to give a low interface friction angle and high interface adhesion. The correct interface parameters can be determined by taking the changes in the normal stress acting on the nail into account.Key words: arching effect, interface friction angle, laboratory test, loose fill, pullout resistance, soil–nail interaction.

Compressibility of foundation fills

The current emphasis on locating building developments on brownfield sites, many of which contain substantial depths of fill, means that the behaviour of fills which support the foundations of buildings is of increasing importance. This paper is concerned with the one-dimensional compression behaviour of these foundation fills. Shallow foundations normally rest on partially saturated ground where the major hazard is associated with settlement due to effects other than structural loading. Consequently consideration is given not only to compression induced by an increase in applied stress, but also to compression consequent on an increase in compressibility associated with an increase in moisture content. A programme of laboratory oedometer tests has been carried out on colliery spoil, an opencast mining mudstone backfill, and a boulder clay fill. The test results have given an improved understanding of fill behaviour in one-dimensional compression and, in particular, the effects of partial saturation on the relationship between applied stress and induced strain. The tests have confirmed that vulnerability to collapse compression on inundation will usually be the most significant hazard for buildings founded on fill. Most types of partially saturated fill are susceptible to collapse compression under a wide range of applied stress when first inundated if they have been placed in a sufficiently loose and/or dry condition. Although creep compression can be a problem in some loose fills, collapse will usually be the more serious hazard. For fills placed dry of Proctor optimum moisture content, collapse potential is principally a function of relative compaction.

Compressibility of foundation fills

The current emphasis on locating building developments on brownfield sites, many of which contain substantial depths of fill, means that the behaviour of fills which support the foundations of buildings is of increasing importance. This paper is concerned with the one-dimensional compression behaviour of these foundation fills. Shallow foundations normally rest on partially saturated ground where the major hazard is associated with settlement due to effects other than structural loading. Consequently consideration is given not only to compression induced by an increase in applied stress, but also to compression consequent on an increase in compressibility associated with an increase in moisture content. A programme of laboratory oedometer tests has been carried out on colliery spoil, an opencast mining mudstone backfill, and a boulder clay fill. The test results have given an improved understanding of fill behaviour in one-dimensional compression and, in particular, the effects of partial saturation on the relationship between applied stress and induced strain. The tests have confirmed that vulnerability to collapse compression on inundation will usually be the most significant hazard for buildings founded on fill. Most types of partially saturated fill are susceptible to collapse compression under a wide range of applied stress when first inundated if they have been placed in a sufficiently loose and/or dry condition. Although creep compression can be a problem in some loose fills, collapse will usually be the more serious hazard. For fills placed dry of Proctor optimum moisture content, collapse potential is principally a function of relative compaction.

A numerical investigation of the stability of unsaturated soil slopes subjected to transient seepage

Abstract Slope instability in unsaturated residual soils and loose fills has attracted increasing attention in recent years around the world such as Brazil, South Africa, Japan and in the Far East. Rain-induced failures are the most common ones. Rainfall leads to the development of perched water table, rising the main groundwater level and soil erosion (due to concentrated water flow), resulting in an increase in pore water pressure or a reduction in soil matric suction. This, in turn, results in a decrease in shear strength on the potential failure surface to a point where equilibrium can no longer be sustained in the slope and then failures occur. However, the present understanding of the influence of transient seepage in unsaturated soils, due to water infiltration under various boundary and ground conditions, and hydrogeological regimes on slope stability is still relatively poor compared with other elements of geomechanics. To investigate the influence of various rainfall events and initial ground conditions on transient seepage and hence slope stability, a parametric study has been conducted using the finite element method. A typical steep unsaturated cut slope in Hong Kong has been adopted for the parametric study. Variables considered in the parametric study include isotropic and anisotropic soil permeability, initial water table at upslope boundary, rainfall intensity and duration. Pore water pressures or suctions predicted during the transient seepage analyses are then used as input ground water conditions for subsequent limit equilibrium analyses of the stability of the slope. Factor of safety is calculated using Bishop’s simplified method, with modified Mohr–Coulomb failure criterion to allow for shear strength variation due to the presence of matric suction. Infiltration due to rain water causes a reduction of matrix suction, but an increase in moisture content and soil permeability in unsaturated soils. Perched water table is developed above the main water table. The factor of safety is not only governed by the intensity of rainfall, initial ground water table and the anisotropic permeability ratio, but it also depends on antecedent rainfall duration. A critical rainfall duration can be identified, at which the factor of safety is the lowest.

Ultrastructure of the flame bulbs and protonephridial capillaries of Prorhynchus (Lecithoepitheliata, Prorhynchidae, Turbellaria)

The flame bulb of Prorhynchus is formed by a single cell. Its nucleus is not located in the cytoplasm at the base of the flame. Cilia of the flame have cross‐striated hollow ciliary rootlets converging towards their tips. The maximum number of cilia counted was 13. The weir consists of a single row of longitudinal ribs that contain longitudinal filaments and possess regularly arranged protrusions along their surface appearing as transverse bands in horizontal section. A ‘membrane’ of extracellular material extends between the ribs. and loose material fills the places between the ribs, with a denser layer midway between adjacent ribs. Distally, the ribs fuse to form a continuous tube without a junction. Small protonephridial capillaries lack junctions, larger ducts have lateral flames and patches of long microvilli. Large excretory ducts open into a ciliated and lamellated cavity which is connected by a narrow canal to the excretory pore. The terminal part of the canal close to the pore possesses many cilia and microvilli. Phylogenetic implications of the findings are discussed.

Grouting in Difficult Soil and Weather Conditions

Several methods of soil grouting and conventional underpinning are used to stabilize subsoils and repair the foundations of three apartment buildings. Innovative cold weather compaction grouting techniques were used in difficult soil conditions to densify poorly compacted man‐placed fill and soft organic silts beneath building foundations. Penetration grouting using a Portland cement slurry and Pozzolan (flyash) is performed to reduce permeability of the upper subsoils and to fill ineffective and detrimental building perimeter drains. A gravel intrusion jacking method is used to further density upper soils in conjunction with conventional underpinning methods. The project is unique because: (1) Techniques were used that allowed the contractor to drill and densify loose fills and soft natural soils containing cobbles and boulders; (2) the contractor was able to perform grouting and underpinning under extremely adverse weather conditions by using special equipment; and (3) occupants were able to remain in buildings during remedial construction.

Stabilization of loose man-made fills by grouting : Coumoulos, D G; Koryalos, T P Proc 10th International Conference on Soil Mechanics and Foundation Engineering, Stockholm, 15–19 June 1981V3, P633–636. Publ Rotterdam: A. A. Balkema, 1981

Stabilization of loose man-made fills by grouting : Coumoulos, D G; Koryalos, T P Proc 10th International Conference on Soil Mechanics and Foundation Engineering, Stockholm, 15–19 June 1981V3, P633–636. Publ Rotterdam: A. A. Balkema, 1981