ABSTRACT: Soil nailing is an in-situ reinforcement technique that has been widely used in the stabilisation of slopes and excavations by retaining in-situ soils with metallic bars or relatively small fully bonded inclusions. Soil nails are normally subjected to tension, shear forces and bending moments across the potential soil slip planes, between the active and stable zones. Field measurements were made on the lateral deflection of the wall supported by driven steel tubes and soil deformation parameters were back analysed. This paper is an attempt to investigate the possible working mechanism using finite element analyses and the significance of bending stiffness of soil nails in an excavation in soft residual soils. Finite element analysis and measured field data indicated that bending moment has a significant role in restraining the lateral displacement of the wall during the excavation process and possibly at its ultimate limit state as well. The outcome of this investigation is that lateral bending has significant effects as the reinforced soil approaches failure and analytical procedures developed should accurately mimic the progressive change in the working mechanisms. INTRODUCTION The use of soil nailing in excavations and slope stabilisation has gained wide acceptance in Southeast Asia, specifically in Malaysia and Singapore due to its effectiveness and huge economic savings. With various development schemes on-going in this region, this method has been extensively used in areas where the soil type is compatible with soil nailing such as residual soils and stiff cohesive soils of low plasticity. Recommendations Clouterre (1993) cautioned the use of soil nailing in soils containing high quantities of clay where moisture content might increase after construction. These restraints is based on the thinking that soft soils will creep significantly over long term and decreased in pullout resistance.

ABSTRACT: Reinforcement elements have been increasingly used in Geotechnical Engineering practice. The use of scrap tires as a reinforcement element is an attractive solution that combines the advantage of improving soil mechanical behavior, with environmental concerns. Scrap tires are globally produced in increasingly large amounts, resulting in an urban solid waste, which requires a specific disposal policy. The reinforcement system with scrap tires is made of a layer of tires filled with soil and tied together with ropes. Compared to metal strips or geotextile sheets reinforcement techniques, this system provides a better adherence between the reinforcement and the soil. This paper presents the results of pull-out tests, performed with several arrangements of scrap tires, subjected to confining levels varying from 0,5 to 1.5 meters of soil surcharge. Most of the tests made use of tires with one sidewall removed. Considering the magnitude of the required loads, a permanent steel structure with a pull-out capacity to 500kN was constructed for the present testing program. The pull-out tests were performed with different geometric arrangements, which varied from a single scrap tire to a maximum of 18 tires. INTRODUCTION The technique of soil reinforcement consists of introducing metal strips or geotextile sheets into a soil mass. For stability purposes its length must extend beyond the potential failure zone. The shear stress developed at the soil-reinforcement interface reduces the horizontal thrust on retaining structures, improving their stability conditions. Scrap tires are a solid waste, which are produced in increasing rates every year, in particular at metropolitan areas. Scrap tires have been usually disposed in landfills or tire piles with serious environmental risks. This problem may assume a larger importance in areas of tropical climate with precarious sanitation conditions. Moreover, scrap tire piles consist a serious fire hazard.

ABSTRACT: The intention of this paper is to present the construction method used to build the underground road crossing, that is a part of the revamping project of "Praa XV", in the city of Rio de Janeiro, and discuss the monitoring results obtained through instrumentation data. An alternative construction method was proposed and successfully executed, allowing reduction of embedded lengths of diaphragm walls and avoiding the need for temporary support. This innovative method distinguishes itself from the original design by using jet-grouting and introduces the following features: smaller and thicker diaphragm walls, temporary support elimination, no need of ground water level lowering and reduction of the bottom slab thickness. In this alternative diaphragm walls constituted the retaining wall, while the columns of jet-grouting were disposed as to form the support. INTRODUCTION To provide the revamping of "Praa XV", located in Rio de Janeiro downtown, it was built an underground crossing for vehicle passage. The square area covering 50 thousand square meters of esplanade was totally re-built in order to create a large playground for the population. Basic design of the underground crossing set up the execution of a trench, with variable width as shown in Figure 3 and 5.5m excavation executed through the inverted method, which consists of excavating under the ground slab, that would support the retaining wall. Such diaphragm walls 60 cm thick, besides the fact that they have been used to retain the soil, it would also be used as complementary foundation for ground slab; barrettes would be used as central supports. The design, also provided internal water pumping of the excavation, using a deep wells system in other to avoid base failure in the existing sand layer 16.5 meter deep. The bottom slab served as uplift slab supported by diaphragm walls and barrettes.

ABSTRACT: The test construction was performed with large-scale models of embankment and abutment to investigate the behavior of the abutment built on soft ground and the stress in the foundation. Two kinds of abutment, named Type-A without pre-load and Type-B with pre-load, were used in the test construction. The behaviors of the test abutments were analyzed by two-dimensional consolidation coupled FEM. In order to extend the obtained results to the common design of abutment, parametric study was performed by varying conditions such as pre-load height and soft ground layer thickness. Based on the above results, a simple method to predict the behavior of the abutment and the stress in the foundation was proposed, in which the effects of the lateral flow and pre-load were taken into account. The seismic design method of abutment on soft ground was also investigated based on the dynamic FEM analysis. The proposed calculation method can reproduce fairly well the results of the back analysis and parametric study. INTRODUCTION When an abutment is built on the soft ground, the behavior of the abutment and the stress that occurs in the foundation has not been made clear yet. Some studies have been conducted on this problem recently (Mochiduki et. al., 1999a, b). In this study, in order to investigate the behavior of the abutment and foundation built in soft ground and reflect them in the design, the test construction was performed with large-scale models of embankment and abutment supported by the steel pile group in soft ground. The test construction employed two kinds of abutment, named Type-A without pre-load and Type-B with small-scale pre-load to investigate the effect of pre-load. Furthermore, the increase of displacement and stress in the pile due to an earthquake was estimated using the dynamic FEM analysis under undrained condition.

ABSTRACT: A new composite pile foundation, namely composite foundation of steel pile with soil improvement, is proposed to resistant intensive seismic horizontal force and to reduce the environment impact. Soft soil at the shallow depth is improved by cement mixing method and a cemented soil mass can be formed in order to increase horizontal resistance. Steel piles are constructed through the cemented soil mass in order to transmit vertical loads to bearing stratum. The new composite pile foundation can be expected to have great horizontal bearing capacity as caisson foundation. Two in situ specimens were prepared, and horizontal loading tests of the composite pile foundation were conducted to confirm their behavior. Specimens included two steel piles of diameter 0.6m, in which soil was improved by cement mixing method from surface to 8m depth. It is shown that the cemented soil mass and steel piles worked as a mass under some extent displacement. The horizontal bearing capacity was much greater than that of steel pile only. To apply it to practice foundation, a spring model of the composite pile foundation is proposed, and compared with the results tested. Based on in situ test and analyzed results, it is concluded that the spring model proposed can be used for practice problems. INTRODUCTION After the great Hyogoken-Nanbu Earthquake, Japan Highway Association (1995) has revised seismic design specifications. For I site (Rock) and II site (Stiff and Normal soils), the standard response spectra are assigned to 2000gal and 1750gal, respectively. For III site (Soft soil), it is assigned to 1500gal at 0.5–1.5 second period domain. To withstand such intensive seismic force, it may be difficult to design pile foundation at III site due to its low horizontal bearing capacity. Meanwhile, environment of geotechnical engineering becomes more and more strict.

ABSTRACT: The paper discusses the possibility of using the principles of bionics for designing reinforced earth embankments. Practical usage and novelty of proposed approach are shown on the example of number of patented concrete constructions. The results of model tests (method of equivalent material) and computer calculations (Finite Element Method – 2D, Limit Equilibrium Method – 3D), confirm high efficiency of proposed approach. INTRODUCTION Due to wide use of reinforced soil technology in recent years the problem established of effective methods for optimization of the structures and reduction of cost of construction has become real. PRINCIPLE OF EQUALITY IN STRENGTH Stressed-strained state (SSS) of the embankment is characterized by high irregularity both in longitudinal and transversal directions. In this state the strength properties of the materials in different parts of the embankment are used to various degrees. In this case the principle of equality in strength requires to select materials (soil and reinforcement) in such a way that their spatial arrangement should provide uniform SSS and should allow full use of their strength. In general, the solution of this problem is associated with many difficulties and it should be divided into several stages. Improvement of equality of strength as far as the height of the embankment is concerned (plain task, cross section) In order to work out the recommendations as far as rational distribution of reinforcement along the height of the embankment is concerned we have carried out three series of computations using "ARMDAM" program (finite element method, plain deformed state, written by the authors). In the first series of computations the criteria of evaluation of reinforcement efficacy were determined. For this purpose the height position of one layer of reinforcement has been changed and the embankment SSS has been analysed.

ABSTRACT: Fiber reinforcement of soils can reduce displacements due to swelling and shrinking of expansive soils. Described in this paper is a series of laboratory tests performed on fiber reinforced and non-reinforced samples of expansive clay to determine the potential for using fiber reinforcement to resist swell displacements. The testing program includes a series of one-dimensional free swell tests performed on 10.2- cm diameter and 6.4-cm diameter specimens of reinforced and non-reinforced expansive clay using an expansion index test device and fixed ring consolidation cells. Specimens used for this testing program were prepared at different fiber dosage rates over a range of compaction moisture contents. Results of these tests show that inclusion of discrete fibers in expansive clays significantly reduces volume change when subjected to one-dimensional free swell conditions. As a result, there appears to be great potential for reducing the detrimental effects on buildings, earth retaining structures and roadways induced by soils with a high potential for volume change or expansion. The importance of fiber dosage rates and compaction moisture content are discussed and the issue of adequate sample size for testing of fiber reinforced soils are addressed. INTRODUCTION Every year more than 250,000 new houses are constructed on expansive soils. Of these, approximately 60 percent will experience some minor damage, such as cracks in foundations, walls, or walkways. Approximately 10 percent will be seriously damaged, some beyond repair (Keller, 1999). It has been recently estimated that shrinking and swelling of soils causes over $7.0 billion of damage per year in the United States to homes, buildings, pavements, utilities, etc. (Wray, 1995). Furthermore, it is estimated that the susceptible soils exist in about 25 percent of the United States and are found in almost every country of the world (Koerner, 1984).

ABSTRACT: Rapid urban development in the hilly terrain of Hong Kong involves the construction of high-rise buildings, many of which are supported on large diameter bored piles. These piles may sometimes have to be founded in slopes and have to resist severe wind loads during typhoon season. In order to minimise the transfer of lateral load from the buildings to the shallow depths of the slopes, an annulus of compressible material (referred to as sleeving) has sometimes been incorporated between the piles and the adjacent soils. In this paper, three-dimensional (3D) numerical analyses were carried out to examine the interactive effects of sleeved piles on slope stability. In the case of a single pile in a slope with a respectable safety margin, the sleeving technique is shown to be capable of minimising the adverse impact of lateral pile loading on local slope instability compared to an unsleeved pile, particularly under high lateral loading. In the case of a marginally stable slope which is vulnerable to external loading, whether the single pile is sleeved or not would make little difference to the global factor of safety. INTRODUCTION Rapid urban development in the hilly terrain of Hong Kong involves the construction of high-rise buildings, many of which are supported on large diameter bored piles. These tall buildings have to resist severe wind loads during the typhoon season each year. Local instability may be associated with the initiation of plastic deformation at the shallow ground in front of the laterally loaded pile, with development of successive cracks being likely to occur in sand (Uto et al., 1985), and large plastic deformation being likely to occur in clay. Global failure may occur if the soil mass supporting the pile develops a slip surface, accompanied by uncontrolled large displacements.

ABSTRACT: This paper describes the preliminary results of a study of large-scale movements affecting a slope in Northern Apennines, Italy. Slow movements of the slope have been detected since 1970 when two piers of a highway viaduct under construction began slightly to move. The displacements kept accumulating and eventually caused serious structural damage to the viaduct. Recently, the need of restoring the serviceability of the viaduct has raised the issue of predicting the slope evolution and defining appropriate remedial measures. The slope under examination consists of Cretaceous formations, mainly sandstones and marls, laying on highly fissured clay shales, dislocated and disarranged by an intense tectonic activity. Monitoring reveals that slow movements are developing along different shear surfaces at different depths. Site investigations and air photograph interpretation demonstrate that the instability mechanism which affects the slope can be described as a "complex landslide" made up of separate landslides. They originated in the last offshoot of an ancient mass movement but differentiated due to different lithological conditions and geological setting. INTRODUCTION Slow movements of a large slope in the Northern Apennines have been revealed by displacements of a highway viaduct. Since construction in 1976 two piers and the south-eastern abutment have been affected by significant displacements. Deformations of the structures were compensated by periodical repairs but eventually the accumulation of displacements caused serious structural damage, producing the closure of expansion joint among beams. Therefore, the need of restoring the serviceability of the viaduct gave the impulse for detailed studies to assess how the viaduct deformations are driven by instability mechanisms of the slope. Two main geotechnical investigations were undertaken in 1993 and in 1995. In 1995 a ground surface monitoring of a large area around the landslide initiated as well.

ABSTRACT: This paper investigates the mechanism of slope displacement using the results of long-term monitoring of the unstable behavior and failure of a large excavated rock slope with an elevation difference about 300 m. The study also evaluates the influence of joint sets on slope behavior through numerical analysis. Then fundamental points regarding the stability of large excavated rock slopes are introduced as follows. The stability of a large excavated rock slope is greatly influenced by the joints and weak layers in the rock, and the relationship between their positions and the positions of the excavated surface. It is important not to fail to notice signs of instability caused by the influences of them early through long-term monitoring started in the early stages of excavation. Based on such monitoring, the need of actions should be determined such as additional investigations, stability analysis, and design modifications and changes. INTRODUCTION This paper focuses on a case of failure of a large excavated rock slope with a height (an elevation difference) about 300 m. First, the behavior of each part of the slope is analyzed based on the displacement measurements obtained during a period of about 10 years before the failure. Next, each cross section of the slope is modeled by elasto-plastic equivalent continuum analysis to illustrate that the measurements are explainable. And how the unstable behavior of the slope occurred according to the topographical and geological conditions of the respective cross sections is examined. SLOPE DEFORMATION BEHAVIOR BASED ON LONG-TERM MEASUREMENT Geological structure The slope involved in this case study consists of late Paleozoic to early Mesozoic olistostrome: limestone, shale, tuff, and sandstone. The alterations of shale and tuff include lenses of sandstone, and these layers are overlain by olistoliths of limestone.

ABSTRACT: Landslide in intensive seismic zone has its peculiar features. Some slope may be stable under static load (normal state). When the slope is in limit equilibrium state, even a slight earthquake may trigger it to destabilize. An intensive earthquake may directly cause a whole slope to fail. Kangding City is located in the intersection of three famous active seismic belts and thus with frequent earthquake activity. Many earthquakes occurred there in the past and the basic earthquake intensity is IX degree. Frequent earthquake activity directly influences the slope stability in the region, earthquake is the key factor inducing landslide and rockfall. In view of this, dynamic discrete element method (DDEM) is adopted in analyzing the stability of a slope in Kangding City, emphasis is laid on modeling of seismic effects on slope stability. The modeling results indicate that even an earthquake with intensity V degree is enough to cause the front slope to slide, earthquake with intensity IX degree will makes the whole slope to fail and slide. The harnessing engineering is quite effective to earthquake with intensity less than V degree. However, when earthquake with intensity IX degree occurs, the bolting engineering in the steep part will be destroyed first and then the slide-resistant piles and finally the whole slope. INTRODUCTION Baitukan landslide is situated at the east slope of Shaoxiangping, along the left bank of Zeduo river in the vicinity of Kangding City, which is located at the intersection of three active seismic belts, thus with frequent earthquake activities. The landslide is an old rockslide of tremendous dimension. Its length is about 600m and width is about 1300 m. Due to lateral erosion of the Zeduo River, the frontal part of the landslide deposits failed frequently. On 15th June 1995, Kangding City hit by a strong rainstorm.

LANDSLIDES IN THE RUSSIAN FAR EAST Landslide research has a big practical meaning for the Russian Far East, since the disturbance of slopes and the formation of landslides cause significant risks in the building development of the region Landslide processes cause direct and indirect damage to the cities, endanger buildings, transport facilities, main pipelines, cause accidents and destruction sometimes accompanied by human casualties. Landslides affect 15 to 95% of the sloping area on the Amur river banks in Khabarovsk vicinity. The paper examines the peculiarities of landslides resulting from the influence of human activities in the Far East, analyses the landslide danger to urban constructions, and evaluates experience in the engineering protection of the territory from landslides. It profoundly analyses landslide processes, structure, formation reasons characteristic of the Russian Far East as well as demonstrates the importance of educating students of Geological, Architectural and Construction departments with regard to the danger of landslides. REGIONALIZATION OF THE TERRITORY ACCORDING TO THE CHARACTER OF LANDSLIDE PROCESS To identify the charakter of development of landslides and other dangerous geological processes on the explored territory of the Far East a geo-engineering regionalization was undertaken. Regionalization is a result of complex geo-engineering research with the use of main methods of Engineering Geology, such as field and laboratory observations, measurements of composition and characteristics of rocks, geoengineering mapping, methods of evaluation and forecast of slopes stability and others. Systematization of landslide affected territories is made on the basis of the main criterion – geological structure – and the important characteristics, such as factors of landslide formation and the mechanism of landslide displacement. In spite of the fact that for each slope there exists individual peculiarities in the structure, the general features of big groups of slopes were considered, in order to determine the characteristics of the landslide process.

ABSTRACT: Between July and October 1998 three separate landslides affected SH3, one of New Zealand's strategic highway routes. At the July slip the highway dropped approximately 5m as 320,000 m3 to 600,000m3 of material adjacent to, and including, the highway slipped affecting around 8ha of land. The landscape of the area is one of rugged high hill slopes of steep rolling country, with limited vegetation cover and highly erodable soils. Native bush was cleared many decades ago to form this essentially sheep farming area. The topography is steep with gully development formed by transitional slides and debris flows within the overlying colluvium. As a major strategic highway in New Zealand's North Island, the reopening of the road and its reinstatement were paramount and urgently needed. Options for the permanent reinstatement needed to take account of the hostile climatic conditions, short construction period and general difficulty in treating local materials for earthworks use. The selected options for the slips included two mechanically stabilised earth (MSE) walls. This paper considers the geological context of the project, the failure mechanism and remedial options, together with a detailed assessment of the adopted MSE walls which were completed and opened to traffic after a three month construction period. LOCATION Stockman's Hill is located on State Highway 3 (SH3), approximately 12km south-west of Piopio and some 100km north east of New Plymouth (Figure 1). SH3 is part of New Zealand's main transport corridor providing access from the Auckland, Hamilton and the Bay of Plenty to the Taranaki Region in the south-west of the North Island. The initial slip (Stockman's I) occurred on 8 July 1998 when a 120m– 150m section of SH3 dropped 5m as adjacent land on the eastern side of the road slipped downslope immediately closing the road to traffic.

ABSTRACT: The South East Transit Project (SETP) involved the construction of a dedicated busway that connects the southern suburbs of Brisbane to the central business district. In many areas along the route the busway corridor was constrained by the urban environment. Much of the proposed busway was located immediately adjacent to the existing Queensland Rail (QR) embankment, creating an extension of the existing embankment to the west. Within the Southbank area a 7 metre high reinforced soil wall was required in the narrow corridor between the QR embankment and an existing TAFE building. In this area, the embankment was located over a deep alluvial channel. The results of analysis indicated that the placement of the SETP embankment would produce 70mm of settlement at the closest rail line. In addition, the TAFE buildings located within 10m of the SETP embankment would experience lateral movements of up to 60mm. Two design alternatives at this location are discussed. The first includes a movement control design where stone columns combined with timber piles were investigated to confine movement within the corridor. The second was a load control design where a piled raft solution was investigated and later adopted for construction. The embankment was constructed as part of an early works package and therefore time constraints governed the methods of design. The results of instrumentation are also discussed as settlement plates, piezometers and inclinometers provided feedback during construction. LOCAL GEOLOGY Based on the various geotechnical studies carried out at this area, the basement rock was found to be part of the Neranleigh – Fernvale Beds of the Palaeozoic age (Main Roads, 1998). The Neranleigh – Fernvale formation consists of slightly metamorphised argillite with minor greywacke and quartzite. The subsurface profile on the eastern side of the QR embankment was obtained from the adjacent Southbank development (Golders, 1998).

ABSTRACT: In this paper an attempt has been made to simplify the complex interface pullout mechanism using nonlinear elastic formulations. Formulations of interface pullout tests are expressed in non-dimensional terms for general applicability. Concepts of relative stiffness and displacement parameters are defined to explain the non-linear pullout response. Comparative parametric studies were carried out for a range of relative stiffness and bond resistance. Normalised load - displacement relations and the variations of pullout force and displacements with distance, are expressed in finite difference equations and solutions presented graphically. The predictions based upon a hyperbolic relation for shear mobilisation are compared with those from the elasto-plastic model. It was observed that the formulations might be used for small to large strain problems i.e., for inextensible to extensible reinforcements. Evaluated results of laboratory and field pullout experiments for steel straps, geotextiles, polymers and nylon geosynthetics are summarised. INTRODUCTION Earth reinforcements are increasingly used in offshore/harbour structures, retaining walls, embankments, landfills, liners, foundations, in-situ slopes, excavations and road construction. New developments in the innovative use of geosynthetics have offered engineered solutions for reinforcement, drainage, separation and stabilisation. This has resulted in the applications of the theory to practice of numerous earth structures, such as slopes and embankments, retaining walls, foundations and dams. There have been many hypotheses postulated about the load transfer and interaction mechanisms but none fully explain the phenomena. Major applications of reinforced soil are retaining walls and steep slopes where the reinforcement provides short term as well as long term stability over the design life of the reinforced soil structures. Figure 1 illustrates typical examples of reinforced soils. FORMULATIONS REVIEWS To understand the behaviour of reinforced earth various laboratory tests such as triaxial, direct shear, pull-out and physical model tests were investigated and used by many researchers.

ABSTRACT: The paper presents the results of two extensive research programmes on shallow and deep foundations installed near slopes. Two approaches are combined in these studies: physical modeling in the LCPC geotechnical centrifuge and FEM analyzing using the CESAR-LCPC code. The first part of the paper deals with the bearing capacity of strip or rectangular footings installed near slopes and supporting inclined and/or eccentric loads. Results obtained by both experimental and numerical approaches and compared and new rules are proposed to take account the slope effects on the bearing capacity. The second part of the paper presents an experimental study of piles installed in slopes and subjected to lateral loads. Horizontally loaded piles are usually designed by p-y curve methods. The aim of the programme is to determine coefficients that should be applied to the p-y curves of the reference pile (installed in flat ground) to take into account the presence of the slope. Soil reaction p and pile displacement y are derived from the bending moments measured on the piles during loading. The responses of the reference pile and of piles installed at different distances from the slope are compared and coefficients are proposed for practical applications. INTRODUCTION The proximity of slopes has a strong effect on the response of shallow and deep foundations. Most of the current codes propose to design foundations near a slope in two steps. The bearing capacity and the settlement are first calculated assuming that the same foundation is resting on flat ground (reference foundation). Then, the effect of the slope is taken into account applying multipliers or reduction coefficients to the computed values. The first step is easily done from laboratory or in-situ test results and all codes of practice indicate the procedure to design the reference footing.

ABSTRACT: Geotechnical studies were conducted for the Vincent Thomas Bridge as a part of the seismic retrofit design program. The foundation of the bridge tower is located immediately next to a channel edge and is supported on a group of 167 piles. Site stability of the channel edge would have significant impacts on seismic performance of the bridge. Using design ground motions adopted for the bridge retrofit program, deformation analyses have been conducted to estimate permanent displacements of the slope. Newmark's sliding block analysis was used along with seismic coefficient time histories computed from two dimensional site response studies which account for compliance of the slope and spatial variation of motions within the soil block. With the estimated free-field ground displacements, pile stresses were examined to assess pile survivability due to kinematic loading from the deep-seated ground failure. INTRODUCTION The Vincent Thomas Bridge, constructed in the early 1960's, is one of the seven major toll bridges in the State of California to undergo seismic retrofit by the California Department of Transportation (CALTRANS). The bridge is located at the entrance to the Port of Los Angeles and is a cable-suspension structure, approximately 1848 meters long. The main suspended span is 457 meters and crosses over a major shipping channel for the Port. The main cables of the bridge rest in saddles at the towers and at the cable bents. The cables are then connected to massive anchorage blocks that are supported on battered pile foundations. The towers are tapering cellular shafts of 102 meters in height supported also on pile foundation at the edge of the channel. As a part of port improvement by the Port of Los Angeles, the channel would be deepened from the existing 10 meters water depth to 15 meters to allow passage of larger container vessels.

ABSTRACT: Strata behavior and control in inclined coal seam face are studied with the following methods: field monitoring of strata behavior is carried out at a working face; Model test on equivalent material is made along dip direction of face and both strata movement and stress redistribution are analyzed and described; Overlying strata movement and fracture are modeled by discrete element method (DEM). The following conclusions may be drawn: Inclined dip angle of coal seam leads to asymmetry of the movement and fracture of overlying strata as well as the abutment pressure distribution; The gob is filled with caved debris differently; the lower end is fully packed, whereas the upper end is however in vacant condition. In the dip direction, the roof is supported by the caved debris quite differently, which results in differentiate roof deflection. The roof at the lower part will not break, but will certainly break at the upper face end, which leads to intensive strata movement in the upper end; Roof movement is much more remarkable in inclined coal seam than that in gently inclined seam. It is therefore strongly recommended that the supports in longwall working face be set with higher stability to keep them sound. INTRODUCTION Meanwhile the rolling blocks may have impact action to the face support; (2) Face floor may fail and shear displacement may occur along bedding plane in sip direction, which as a results has negative effects on support stability; (3) Due to uneven filling of gob by the caved debris, roof behaves quite differently in the dip direction characterized by intensive roof movement at the middle and upper section; (4) More remarkable anisotropy rockmass, which makes gateway deform and fail with distinguished direction.

ABSTRACT: A method for predicting the pull out load Ð end displacement behaviour of geogrid reinforcement embedded in sandy soils using a nonlinear finite difference approach is presented in this paper. In this method, the soil was modelled as an elastic-perfectly-plastic Mohr-Coulomb type material and the reinforcement was modelled as a linear elastic cable. The soil - reinforcement interaction was modelled by a spring-slider interface system with shear stiffness and shear capacity properties. Details of the numerical model and the method for selecting the soil-geosynthetic interface properties for predicting the pullout behaviour are discussed in the paper. The pullout behaviour of three types of geogrids under different surcharge loads was analyzed and the results compared with laboratory test data. The measured and calculated pullout load Ð displacement responses agreed reasonably well for all the cases examined. The pullout capacity predicted by the proposed method agreed more closely with the measured values than the two existing methods. The proposed method appears more beneficial because of its ability to predict the entire pullout load -displacement response in addition to pullout capacity. INTRODUCTION It is essential to know the pullout behaviour of geosynthetic reinforcement embedded in soils for designing geosynthetic reinforced soil structures efficiently (e.g., for assessing the length of reinforcement in a reinforced soil wall). NUMERICAL DETAILS AND SELECTION OF INTERFACE PARAMETERS A finite difference stress analysis program known as FLAC, Fast Lagrangian Analysis of Continua (FLAC 1998), was used for the analysis. In this program, the equations of equilibrium and stress strain behaviour are expressed in finite difference form and are solved by an explicit iterative scheme. The analysis is inherently incremental and can be taken to collapse/failure along a user prescribed path. The numerical principles of FLAC-analysis are detailed in Cundall & Board (1988).

ABSTRACT: Using a newly developed large ring-shear apparatus, a series of tests was conducted on silty soils to study their undrained shear behavior. The samples were made by mixing loess into a fine-graded silica sand with 10, 20, and 30% loess by weight. By performing tests at different initial void ratio, the undrained shear behavior of samples with different loess contents at loose and medium-dense states was presented and discussed. Basing on the tests results, effects of loess contents on the peak and residual shear strengths are examined. It was found that adding loess into the host sand could lower the peak and residual shear strengths; and these two strengths decreases with increasing loess content. Meanwhile, with increasing loess content, the dissipation of generated pore pressure from the shear zone becomes remarked slower when the shear box was turned into drained conditions, and there is little, if any, dissipation for tests on the mixture with 30% loess. INTRODUCTION A fluidized landslide is usually characterized by high mobility and long run-out distance, and then followed by tremendous hazards. It is always the result of liquefaction, a process during which high pore water pressure is generated and soil mass loses a great part of its strength and shows the behavior of liquid. Therefore, research on this kind of failure has been mainly focused on liquefaction potential analysis with emphasis on the undrained shear behavior of soils. However, compared with those tests on clean sand, the undrained shear behavior of silty soils is less studied, although it has been pointed out that silt and silt-clay mixture are more prone to suffer from liquefaction failure with large resulting run-out distance, basing on many field observations (Bishop, 1973; Eckersley, 1990; Ishihara, et al., 1990; Zlatovic and Ishihara, 1995).