Row Of Piles Research Articles

Effects of pile rows on vibration reduction in nearly saturated soil

This paper presents an analysis about the vibration reduction effects by a barrier in a nearly saturated soil medium. The barrier is assumed to consist in an arbitrary distribution of parallel cylindrical piles embedded in an infinite nearly saturated soil. Based on the equations governing the motion of nearly saturated soil, the complex wave numbers and amplitude ratios between the liquid phase and solid phase are first derived according to the Helmholtz decomposition theorem. With the aid of the Graff’s addition theorem, the unknown multiple complex scattering coefficients by an arbitrary configuration of piles as barriers are determined by taking an advantage of the boundary conditions at pile-soil interfaces and the linear independence of trigonometric functions. Then the corresponding expressions for the nearly saturated soil displacements at both sides of the pile rows can be obtained. The numerical results show that soil saturation degree and permeability exert significant influences on the isolation effectiveness of pile rows, and that the distance between neighboring rows is crucial for the isolation effectiveness. The isolation rules can provide useful guidelines to the design of pile rows as barriers in nearly saturated soil.

Modeling of Batter Pile Behavior under Lateral Soil Movement

Pile foundation is frequently used when structures are located on weak sublayers or are at risk from lateral loadings such as earthquakes. The design of pile foundations has recently become crucial to stop slope movement. To understand the behavior of pile foundations subjected to lateral soil movement, the three-dimensional Fast Lagrangian Analysis of Continua (FLAC3D) program was used to perform numerical simulations, which can reduce the cost of field testing. Vertical piles and batter piles were combined into 3 × 3 pile groups, and the response of batter piles to soil movement was analyzed. The outer batter piles led to an increased bending moment in the middle, vertical pile row. Increasing the pile spacing and the presence of battered piles reduced the pile group’s displacement. The batter pile group’s maximum bending moment was smaller than the vertical pile group’s in sand soil, but 5–8 times higher in clay soil.

실내모형시험을 통한 사질토 지반에서 군말뚝과 터널의 수직 이격거리에 따른 하중분포 및 지반거동 분석

도심지에서의 터널굴착은 상부구조물과의 상호거동에 대한 이해가 필수적이다. 도심지에 사용중인 대부분의 구조물은 말뚝기초로 상부의 하중을 지지하고 있어, 터널 굴착 시 반드시 영향을 받는다. 따라서 본 연구에서는 실내모형시험을 통해 기존의 군말뚝 기초 하부 터널굴착에 따른 축력 분포와 지반의 거동을 분석하였다. 말뚝 기초는 2, 3 열 말뚝으로 가정되었으며, 말뚝 선단부와 터널 천단부의 이격거리는 터널직경에 대한 일반화를 위해 터널 직경(D) 대비 0.5D, 1.0D 그리고 1.5D로 고려되었다. 지반은 약 30%의 상대밀도(Dr)를 가지는 느슨한 사질토로 형성되었으며, 말뚝의 축력 분포를 측정하기 위해 말뚝에 변형률게이지(strain gauge)를 부착하였다. 또한, 이격거리에 따른 군말뚝의 침하와 인접지반의 침하를 변위센서(linear variable differential transformer; LVDT)와 다이얼게이지(dial gauge)를 통해 측정였으며, 터널굴착에 따른 지중의 변형을 근거리사진계측기법(close range photogrammetric technique)을 통해 측정하였다. 수치 해석을 통해 실내모형시험 및 근거리사진계측 결과와 비교 분석하였다. 본 연구에서는 체적손실율(volume loss; <TEX>$V_L$</TEX>) 개념을 이용하여 터널굴착을 모사하였으며, 1.5%로 적용되었다. 연구결과, 이격거리가 멀어질수록 말뚝의 축력감소는 작게 나타났으며, 침하량은 모두 유사한 경향을 나타내었다. 특히, 말뚝 선단부와 터널 천단부의 이격거리가 0.5D에서 1.0D로 증가할 때 축력과 침하량의 가장 큰 감소율이 가장 큰 것으로 나타났다. Tunnelling in urban areas, it is essential to understand existing structure-tunnel interactive behavior. Serviced structures in the city are supported by pile foundation, since they are certainly effected due to tunnelling. In this research, thus, pile load distribution and ground behavior due to tunnelling below grouped pile were investigated using laboratory model test. Grouped pile foundations were considered as 2, 3 row pile and offsets (between pile tip and tunnel crown: 0.5D, 1.0D and 1.5D for generalization to tunnel diameter, D means tunnel diameter). Soil in the tank for laboratory model test was formed by loose sand (relative density: Dr = 30%) and strain gauges were attached to the pile inner shaft to estimate distribution of axial force. Also, settlements of grouped pile and adjacent ground surface depending on the offsets were measured by LVDT and dial gauge, respectively. Tunnelling-induced deformation of underground was measured by close range photogrammetric technique. Numerical analysis was conducted to analyze and compare with results from laboratory model test and close range photogrammetry. For expression of tunnel excavation, the concept of volume loss was applied in this study, it was 1.5%. As a result from this study, far offset, the smaller reduction of pile axial load and was appeared trend of settlement was similar among them. Particulary, ratio of pile load and settlement reduction were larger when the offset is from 0.5D to 1.0D than from 1.0D to 1.5D.

EFFECTS OF VERTICAL WALL BARRIER ON THE RIGID PAVEMENT DEFLECTION OF FULL SCALE 1-PILE ROW NAILED-SLAB SYSTEM ON SOFT SUB GRADE

The weaker part of rigid pavement when it is loaded is the edge of slab. Vehicle wheels thatare often running in/out from/to pavement can cause void in the sub base-pavement interface for a long time loading period. Flexural moment caused by temperatures also precipitate the damages of pavement edge. To avoid the damage of pavement edge, the vertical wall barrier is added. This research is aimed to learn the contribution of vertical wall barrier on the pavement of Nailed-slab System to reduce the slab deflection. Full scale observation was done over models in soft clay soil. The full scale of 1 pile row Nailed-slab System was conducted on soft clay which consisted of 6.00 m x 1.20 m slab area with 0.15 m in slab thickness, 5 short micro piles as slab stiffeners which were installed under the slab. Piles and slab were connected monolithically, then in due with vertical concrete wall barrier on the two ends of slab. The system was loaded by compression loadings on the slab. Deflection of model without vertical wall barrier was analyzed by finite element method. Results show that the vertical wall barrier cannot significantly reduce the deflection for edge loading. It is opposite to the model test result from Puri, et.al. (2011) where the vertical wall barrier can reduce 74% deflection for edge loadings. It is to be expected that numerical application program could not model the vertical wall barrier which lower position than slab level.

Retaining mechanism and structural characteristics of h type anti-slide pile (hTP pile) and experience with its engineering application

Since the 1980′s a new h form type anti-slide pile (hTP pile) has been used to stabilize slopes. This paper describes the first systematic studies about the retaining mechanism and applicability of the hTP, on the basis of the analysis of the soil-pile interaction. Similar retaining structures such as the portal anti-slide pile – PASP and other traditional retaining structures as the anchored anti-slide pile – AASP, the common anti-slide pile – CASP are also considered in this study to analyze the differences between their behavior and that of the hTP and other structures. This study, also analyzes the economy and technology of its construction. Post construction monitoring is conducted to evaluate its final retaining effect. The results show that the retaining mechanism of hTP can be attributed to the form of the structure, the soil mass between the two rows of piles and the soil mass downslope of the hTP. All together they greatly improve the hTP's retaining effect over the traditional structures. The stress distribution of hTP is more appropriate than for the traditional types of retaining structure's due to a decreased stress concentration effect. From economic point of view, the hTP's is also to be preferred over other types of retaining structures. The post construction monitoring results show that when supported by hTP, the slope tends to be stable because a good retaining effect is obtained.

Effect of periodic pile row in subway vibration Isolation

At present measures for reducing vibration by subway are mainly from vibration source, path and building, where vibration isolation on path is an important one. This article studies the effect of periodic pile row in subway vibration Isolation for a planned building close to a subway in Beijing based on phonon crystal theory. First test the vibration of surface field and get the vibration characteristic frequency. Second calculate the attenuation zone of periodic pile row which contains the vibration characteristic frequency, and get the parameter combination of the pile. Third A track-tunnel-soil-building 3D finite element model was established by software ANSYS. Input the force of vibration source calculated by the model of vehicle and guideway coupling. Then use the finite model to calculate the effect of the periodic pile row. The result shows that the working frequency of the periodic pile row is higher than 12Hz. The Damping capacity of the largest Z vibration level is 4.13dB on the first floor, and the Damping capacity becomes greater with the increase of the floor. Periodic pile row based on phonon crystal has a wide vibration isolation frequency and a good vibration isolation performance.

Resource Conservation by Effective Composting of Municipal Solid Waste in Sri Lanka – Optimum Moisture Range for the Bio-oxidative Phase

Waste is a resource. Municipal solid waste management is a great concern in Sri Lanka due to high water content and heterogeneity of the waste. Composting is one of the important, cost effective methods of management of biological waste in developing countries. This study was performed to determine the optimum moisture range for effective composting, which can be maintained throughout the bio-oxidative phase of the composting process to accelerate the decomposition rate and eventually get a better compost product. Four wind row piles were set up with moisture contents adjusted to 60% ± 10% (Control) for five weeks, 40% ± 10% (Pile A), 60% ± 10% (Pile B) and 80% ± 10% (Pile C) for 8 weeks. Moisture content of the control pile was lowered to a value of 40%± 10% during the last three weeks while other piles were maintained within the experimental moisture ranges for the eight weeks of composting cycle. According to the temperature profiles of the piles, pile B showed the best temperature level for microorganisms. Other physico-chemical parameters were not significantly different between piles. Therefore, moisture content of pile B (60% ± 10%) was selected as the optimum moisture range for the bio-oxidative phase in the composting process. Unskilled labourers can maintain that moisture level easily by performing the squeeze test for the moisture.

Lateral pressure on piles due to horizontal soil movement

This paper presents the results of 1g model tests on single piles and pile rows loaded laterally by horizontal soil movements in soft kaolin clay. In soft soil layers, vertical piles are frequently loaded laterally by horizontal soil movements caused by eccentric loading or unloading of the ground surface around the piles. In many cases, the lateral pressure acting on piles due to horizontal soil movements is calculated using empirically or analytically based approaches. The model tests investigate the influence of the roughness of the pile–soil interface, the pile size, the pile shape, the displacement rate of the soft soil flowing around the pile and the pile spacing on the lateral pressure acting on the piles. During the model tests, the soil movements were analysed with the particle image velocimetry method. The results of the model tests show possible influences on the resulting pile loads.

Research on the Bearing Capacity of Double Row Steel Sheet Pile Reinforcement Depth of the Based on Soil between Piles

With the complex force characteristics of double row steel sheet pile retaining structure. Through the PLAXIS 3D finite element model is established, the soil with HS-Small constitutive model, the cement soil reinforcement of double row steel sheet pile support retaining structure of pile soil, the simulation and analysis of the soil between piles reinforcement depth of double row steel sheet piles by the force and displacement. Analysis shows that with the increase of reinforcement depth:1） before and after the peak displacement of two rows of steel sheet pile becomes smaller; 2）outside row of pile axial force variation trend of different;3） outside row of steel sheet pile peak shear force and bending moment increases first and then decreases; 4）the peak reached maximum value when the reinforcement depth have different; 5）internal row pile internal force of absolute value was significantly larger than that of the outer row of piles, should according to the actual needs of the project using the appropriate reinforcement depth.

Retrofitting of steel pile-abutment connections of integral bridges using CFRP

Integral bridges are typically designed with flexible foundations that include one row of piles. The construction of integral bridges solves difficulties due to the maintenance of expansion joints and bearings during serviceability. It causes integral bridges to become more economic comparing with conventional bridges. Research has been focused not only to enhance the seismic performance of newly designed bridges, but also to develop retrofit strategies for existing ones. The local performance of the pile to abutment connection will have a major effect on the performance of the structure and the embedment length of pile inside the abutment has a key role to provide shear and flexural resistance of pile-abutment connections. In this paper, a simple method was developed to estimate the initial value of embedment length of the pile for retrofitting of specimens. Four specimens of pile-abutment connections were constructed with different embedment lengths of pile inside the abutment to evaluate their performances. The results of the experimentation in conjunction with numerical and analytical studies showed that retrofitting pile-abutment connections with CFRP wraps increased the strength of the connection up to 86%. Also, designed connections with the proposed method had sufficient resistance against lateral load.

Soil Arching Effect in Sand Reinforced with Micropiles Under Lateral Load

The mechanics of the mobilization of resistance from passive pile groups subjected to lateral soil movement is discussed from the standpoint of the arching effect. An innovative approach has been attempted to study the effect of introducing multiple rows arrangement of micropiles in sand at varying ground densities (30% and 80%). Similarly, parametric study focusing on the effect of the reinforcing rods cross sections (10 × 10 mm square and 3 mm in diameter piles) was also considered in terms of their pressure resistance. The results reveal that the formation and shape of the arching zone are functions of pile arrangement and pile shape. Group effects in multiple rows of piles are significant, but no significant effect under lateral soil movement (passive loading) for single row of piles was observed in sand.

Bed morphology in vegetated estuarine river with mild-curved meander bend

ABSTRACTIn this study, the effect of single and double row piles for reducing scouring in a mild-curved river meander was studied experimentally. The experimental study focused on the effect of vegetation on bed topography in a mild-curved meander bend. The experimental tests were conducted in a laboratory flume under clear water flow conditions. A series of experimental tests were carried out with a fixed bed and non-vegetated and vegetated moveable beds with different vegetation patterns. Analysis of the flow characteristics indicated that when the bed was mobile with vegetation on the inner bank, the core of maximum streamwise velocity shifted towards the centreline of the bend. Additionally, the cross-sectional kinetic energy increased from 0.05% for the fixed-bed test to 4.30% for the test with a double row of vegetation. Furthermore, the presence of vegetation was found to increase the uniformity of the distribution of turbulence intensity and to reduce the Reynolds shear stress along the test section. Also, the mass fluxes increased from the outer bank to the inner bank and from the upstream towards the downstream of the bend. Finally, comparison of bed topography in vegetated and non-vegetated channels showed that the maximum scour depth at the bend apex was reduced by 77% and 62% for the cases with one row and two rows of vegetation, respectively. The results of this study were compared with previously proposed models for predicting the vertical distribution of the streamwise velocity at the bend apex. It was found that Johannesson and Parker’s model (JPM) gave the lowest value of standard error. The above findings are useful in river training works and, in particular, for restoration of meandering rivers.Editor D. M.C. Acreman; Associate editor C. Cudennec

Seismic Bearing Capacity of Strip Footings on Pile-Stabilized Slopes

This paper develops an analytical method to calculate seismic bearing capacity of a strip footing, which is located on a slope reinforced with rows of pile. The resistance of passive pile is determined based on normal and shear stress of the soil around the pile, which is then compared to other analytical methods. This comparison indicates an acceptable agreement. The variants of the study include location of pile rows, location of footing with respect to the slope crest, foundation depth, and horizontal seismic coefficient. The footing seismic bearing capacity is calculated based on seismic slope stability with limit analysis method (yield acceleration coefficient of reinforced slope with pile row) as well as soil stability beneath the footing by means of virtual retaining wall method. The main objective is to determine and establish the relation between various parameters and seismic bearing capacities of the footing, and to find the best location of the pile row that gives the best improvement in the footing seismic bearing capacity. Results indicate that stabilizing the earth slope with rows of piles has a significant effect on the improvement of seismic bearing capacity of the footing. In addition, the results of the present method are compared with those, reported by others, to demonstrate a reasonable agreement.

Seismic stability analysis of slope reinforced with a row of piles

In this paper, the seismic stability of a slope reinforced with a row of piles is analyzed within the framework of the pseudo-static approach. Calculations are conducted by using a technique integrated the kinematic theorem of limit analysis with strength reduction concept. The log-spiral failure surface is considered, analytical expressions are derived that enable one to readily calculate the yield acceleration coefficient for the slope subjected to seismic loading, and the lateral stabilizing force provided by piles which is required to increase the slope safety factor to a design value. Numerical results for typical example are presented and the reasonableness of the procedure is verified. Furthermore, discussions are made in order to illustrate the influence of horizontal seismic coefficients on the lateral stabilizing forces and the optimal position of the pile in seismic area.

A rational layout of double-row stabilizing piles for large-scale landslide control

Double rows of stabilizing piles can be applied to large-scale landslide control; however, the geometry of the layout can substantially affect the lateral bearing capacity of the structure. Based on slope slippage and deformation mechanisms, this paper proposes a specific pile layout configuration—an embedded rear-row pile (with the top of the pile embedded to a certain depth in the slope), and a full-length fore-row pile (with the top of the pile on the surface of the slope). This layout appears to be a rational arrangement for resisting a landslide with a polyline slip surface using double-row piles. As for landslides with a linear slip surface, a full-length pile layout of fore- and rear-row piles can be adopted. However, the area of sliding mass directly supported by the rear (upslope) and fore piles should be approximately equal (in plane) to ensure that the thrust force on the piles above the slip surface is close to the optimum condition. Based on a numerical simulation, this paper also discusses a method for determining a rational embedded depth for the top of the rear-row piles for landslides with polyline slip surfaces, as well as a more rational pile structural form in the case of relatively short distances between the two rows of piles. The results obtained in this paper provide theoretical support for a rational layout of double-row piles for large-scale landslide controls, and provide assistance for practical reinforced slope projects.

Stabilizing the Landslide on Road E87 Burgas – Malko Tarnovo, Bulgaria

Bulgaria is a country with a relief of various elevations. This is a precondition for appearance of landslides of different types. The present study deals with stabilizing approaches for a landslide on the road between two towns in Bulgaria.The landslide covers 63 m of the main road connecting the Bulgarian Black Sea capital of Burgas and the border between Bulgaria and Turkey. This road, I-9, is a first-class road which coincides with European Road E87 and passes through Bulgarian territory from north to south.In the spring of the year 2010 two parallel cracks appeared in the road near the km 282+000 mark and the road sank 2,5 m. The terrain of the landslide is steep with an inclination of 36° - 42°. The geological survey shows back filling, slope washed gravels and weathered bedrock to a depth of 12 m. Bed rock of marls is found below this depth. The sliding surface is a polygonal line. Stability calculations are made and an uncompensated landslide load is determined.Different approaches are used for stabilizing of the landslide – piles, anchors, drainage ribs and retaining walls, geo grids as well as their combinations. The typical anchors construction was not possible to be used because of the steep terrain and joint work of two rows of piles was designed instead. The road has been restored and under exploitation.

Interaction of a Railway Tunnel with a Deep Slow Landslide in Clay Shales

The Varco d’Izzo landslide system (Basilicata Region, Italy) develops at the suburbs of the city of Potenza, capital of the region, and is crossed by two transport infrastructures of local importance: the national highway Basentana and the national railway line. This paper is focused on the effects of slope movements on the railway tunnel which was built in the accumulation of an earthflow of the landslide system. The earthflow displacements were slow but continuous in the monitoring period 2005-2015 and in the order of one to several cm/year. They have led, not far from the railway tunnel area, to the eviction of a house, the dismantling of a pedestrian bridge, damages to roads and other structures. The tunnel was completely re-built in 1992 between two rows of piles, by the cut-and-cover method, after the previous tunnel had suffered severe damage due to the landslide. Available inclinometer data seem to suggest that, locally, the tunnel with its piles is hindering landslide displacements. In fact, measurements carried out in the vicinity of the tunnel, upslope from it, do not show a slip surface crossing the piles. On the other hand, landslide displacements are observed both farther, upslope from the tunnel, and downslope from it. The resultant of earth pressures acting on the tunnel is thus, probably, increasing with time. The distribution of landslide displacements around the tunnel until recent years is herein analyzed. Results of site surveys are reported. The causes of the current state of deformation of the tunnel, which was evaluated by laserscanning, are examined with the help of simplified calculations and FEM simulations.

Kinematical Limit Analysis for a Slope Reinforced with One Row of Stabilizing Piles

Stabilizing piles are commonly used to improve slope stability. The load that a pile should sustain and the associated slip surface under a prescribed factor of safety are two critical design parameters in practice. Based on the kinematically admissible failure mechanism, a limit analysis approach is introduced, which considers two potential slip surfaces that individually lie in the upslope and downslope of the piles. The explicit formulas for the upslope thrust force and downslope resistance on a pile are derived, which enables the calculation of the maximum load on a pile and the corresponding critical slip surfaces using a computer program. The maximum load and critical slip surfaces under a design factor of safety are mainly affected by soil properties and five other parameters: location of the pile row, dip angle of the slope face, action point and dip angle of the force, and improvement coefficient of the slope stability. The relevant quantitative calculation can be performed using the proposed method. Moreover, the possible failure with the upslope soil surpassing the pile top under a specified design factor of safety is significantly illustrated in the paper, which is helpful in the rational determination of the location of the pile row.

Centrifuge Modeling of Laterally Loaded Pile Groups in Improved Soft Clay

AbstractA series of centrifuge tests were performed to investigate the behavior of laterally loaded pile groups in improved and unimproved soft clay. The soil profile consisted of four lightly overconsolidated clay layers overlying a dense layer of sand. The pile groups had a symmetrical layout consisting of 2×2 piles spaced at 3.0 and 7.0 pile diameters (D). After improving the soft clay in situ using simulated cement deep soil mixing (CDSM), pile foundations were driven into the improved ground. Centrifuge tests revealed that CDSM is an effective method to increase the lateral resistance of pile foundations. The lateral resistance of the improved pile group at 7D spacing increased by 157%. Due to pile–soil–pile interactions, the lateral resistance in the 3D pile group increased by only 112%. In both improved and unimproved pile groups with 3D spacing, the leading row of piles carried larger loads and bending moments than the trailing row of piles. No group interaction effects were observed in all pile g...

Limit equilibrium analysis of seismic stability of slopes reinforced with a row of piles

SummaryAn approach based on the category of limiting equilibrium analysis is proposed to consider the reinforcing effect of one row of vertical piles on slope under seismic conditions. The approach is based on an uncoupled formulation in which the pile response and slope stability are considered separately. Closed‐form equations are derived, allowing the yield acceleration coefficient to be determined for giving pile characteristics. Results were compared with those obtained using another limit equilibrium method. The effects of pile location on the effectiveness of increasing seismic stability of the slope–pile system were elucidated. It was found out that the piles should be installed in the middle–upper part of the slope to achieve greatest safety, but the pile length and other possible failure modes should be checked carefully in design. Copyright © 2015 John Wiley &amp; Sons, Ltd.