Row Of Piles Research Articles

Research on the Mechanical Properties of New Double-Row Pile Supporting Structure Based on an In Situ Study

According to the force characteristics of the double-row pile supporting structure, two new types of double-row piles are developed: the prestressed strong-constrained double-row piles and the recycling assembled double-row piles. A comparative field test was conducted on the support effects of the two new double-row piles and conventional double-row piles. The test site is located in a deep foundation pit of the Beijing Daxing International Airport Project. The feasibility and reliability of the two new support structures are verified. Field monitoring included section strain and bending moment of the pile body, horizontal displacement of the pile body, and vertical and horizontal displacement of the pile top. The research shows that because of the prestressed anchorage cables in the rear row piles, the prestressed strong-constrained support structure can provide better tensile performance from the rear piles, and the deformation and displacement are minimal. The recycling assembled double-row piles have similar deformation and displacement to the conventional piles. Through the connection of the steel members, the construction time can be effectively shortened. After the backfill of the foundation pit, the steel members can be recycled and the cost can be reduced.

Prediction of rainfall-induced landslide movements in the presence of stabilizing piles

Among the different techniques usually employed to stabilize landslide bodies, the use of one or more rows of piles firmly embedded in the stable portion of the slope is commonly considered a reliable and effective measure. Nevertheless, a landslide may still be reactivated by an increase in the groundwater level due to rainfall. In this context, a novel method is proposed in the present study for a preliminary evaluation of the rainfall-induced movements of landslides in the presence of stabilizing piles. This method uses a water balance equation to evaluate the groundwater level changes due to rainfall, and the motion equation to relate these changes to landslide displacements. The piles contrast the landslide movements by a passive resistance force the value of which depends on the pile–soil failure mode and pile arrangement. The proposed method appears attractive from an engineering viewpoint, since it can be readily implemented in a common electronic sheet and requires few parameters as input data. Most of these parameters can be obtained from conventional geotechnical tests, whereas the remaining ones should be calibrated on the basis of available measurements of rainfall, groundwater level and soil displacement. After performing this parameter calibration, the method may be employed for predictive purposes to relate future landslide movements to expected rainfall scenarios. The predictive capability of the present approach is assessed by comparing the results with those observed in a published case study concerning a landslide body periodically reactivated by rainfall, in which a row of stabilizing piles was installed. • The paper deals with landslides reactivated by rainfall. • A method is proposed for predicting landslide movements in the presence of piles. • The method directly relates rain recordings to landslide movements. • The method is simple and can be readily implemented in a common electronic sheet. • One or more rows of piles are able to reduce the landslide mobility of about 70%.

Centrifuge modelling of the use of discretely spaced energy pile row to reinforce unsaturated silt

Discretely spaced reinforced concrete (RC) energy pile rows have been proposed to be installed at the mid-height of soil slopes. Although the pile row can provide mechanical reinforcement to slopes, the piles can also potentially be used to (a) intercept solar energy from roadways for heat storage in the ground to mitigate extremely high carriageway temperatures and (b) to extract shallow geothermal energy for road surface de-icing. In this study, a series of centrifuge model tests was conducted to evaluate the shearing behaviour of unsaturated silt with and without reinforcement by conventional piles and energy piles. Three-dimensional finite-element coupled water–vapour–heat transport analysis was also performed to understand further the effects of pile heating on the responses of temperature and pore-water pressure of the soil. The measured and computed results revealed that the primary effect of pile heating was an increase in soil hydraulic conductivity due to the heat-induced reduction in water viscosity. The heated soil had enhanced water flow and hence developed higher suction. When subjected to translational slip, the silt reinforced by a row of closely spaced RC energy piles exhibited a more ductile shearing response and a lower peak shear resistance, compared to that reinforced by conventional piles. The peak bending moments mobilised in the energy piles in the stable stratum were also smaller. At larger shear displacements, however, the shear resistance converged to a similar value, regardless of the suction and temperature. These findings suggest that piles modified with additional energy transfer functionality can continue to act as reinforcement, potentially preventing soil from a sudden brittle failure, without attracting additional flexural stresses onto the piles.

Non-dimensional solutions for the stabilising piles in landslides in layered cohesive soils considering non-linear soil–pile interactions

The pile response is of great importance to the effectiveness of a row of piles used as a landslide mitigation method. However, the current classifications of the pile responses and failure modes do not consider the effects of soil displacement and the relative pile rigidity. An attempt is made in this paper to improve this using a non-dimensional model based on simplified ground consisted of two layers of cohesive soils. A hyperbolic p–y model is adopted to consider non-linear soil reactions. The calculations of three case histories show that the proposed model predicts the pile responses well. The dependencies for obtaining a pile response with maximum pile resistance have been identified and the influencing factors have been examined. The efficacy of the proposed approach has been demonstrated by the satisfactory result that it achieves in reproducing the more complex three-dimensional finite-element analyses. The application of the non-dimensional solutions indicates that it can increase the efficiency of the preliminary pile design.

Numerical Investigation of Soil Arching in Dense Sand

Soil arching is relevant in various engineering applications particularly in cases where there is relative movement between soil and structure. When a portion of the soil mass yields, redistribution of stresses take place between the yielding mass and its surrounding. Several trapdoor experiments have been performed with different improvements and extensions over the past few decades to study soil arching. Numerical modeling of a trapdoor mechanism is performed in this study and the suitability of Hardening Soil constitutive model over the Mohr-Coulomb model has been studied. In the present study, extensive parametric studies were conducted to examine the extent of the zone of influence and zone of yielding. The zone of influence, beyond which there is no influence of soil arching, is bounded by straight lines to form a trapezoidal shape. The dimensions of the influence zone depend on the fill height (H) and trapdoor width (B). The two families of failure surfaces, internal and external, are described and their categorization with respect to the H/B ratio is well explained. Furthermore, the zone of yielding and the region enclosed within limits of influence and failure planes are classified as active and passive zones, considering the dilation and compression in the direction of trapdoor displacement. The equilibrium of stress transfer in soil arching that remained as an unjustified assumption until now is systematically brought out in the present study. The present study also highlights salient characteristics of the plane of equivalent settlement and critical height. The present study throws some light on the need for further understanding of arching in various field applications, such as piled embankments, tunnels, culverts, buried pipelines, excavations supported by contiguous pile walls, and slopes stabilized by a row of piles.

Failure Analysis of a Highway Cut Slope with Anti-Slide Piles

Landslides induced by engineering construction are very common in reality; it is necessary to clarify the causes of landslide failure to avoid similar accidents. A landslide induced by highway construction is taken as a case. Field observations, data collection, and analyses were used to investigate the deformation and causes of the landslide. The failed slope is mostly comprised of gravel soil, there were some shear cracks on both sides of the slope before sliding, and most tensile cracks were connected with shear cracks after sliding. The cut slope of this highway was designed to be protected by prestressed anchor sheet piles. However, in the construction process, the slope in front of the antipiles was removed when the piles were constructed without any anchor cables, which led to the shear damage of a row of anti-slide piles with a 15-meter-long cantilever. Moreover, continuous rainfall over several days aggravated the landslide damage because of increase of the self-weight and degradation of the mechanical parameters of the slope materials. The mechanical and simulation analyses both show that the resistance provided by the cantilever piles was not enough to prevent the force behind the piles. The irrational construction process and rainfall caused the slope failure.

Influence of lateral cyclic loading on the piled-raft foundation embedded in layered soil

The work includes an experimental analysis was performed to determine the impact of several variables on the behavior of laterally loaded piled raft model (2×2) having a ratio of length to diameter (L/D=40) and a diameter spacing (S / D) ratio of 3, 5 and 7 at frequency (0.2) Hz embedded in layered soil. The results are submitted as load-deflection curves and bending moment profiles. The effects of degree of saturation, number of cycles, level of cyclic loads, and the location of piles in a row are studied in this work. The results illustrated that increasing degree of saturation for clay soil (mid-layer) decreasing the lateral resistance of this model by about (25%, 31%, and 39%) for S/D=3, 5, and 7 respectively and bending moment by about (7%, 15%, and 17%) for S/D=3, 5, and 7 respectively. The piles in the front rows resist the soil with its full capacity, while in the trailing rows (i.e back) the shadowing effect tends to cause a reduction in soil resistance. The results clarified that maximum bending moment for trailing row less than the leading row by about 7%. The presence of vertical loads lead to an improvement in the lateral resistance of the model with dry clay soil about (28%, 26% and 12%) for S/D=3, 5, and7 respectively, whereas the increase in the horizontal resistance of the model with partially saturated clay soil about (40%, 45%, and 44%) for S/D=3, 5, and 7 respectively, compared with the absence of vertical loads.

Theoretical analysis and engineering application of the new pile-soil-support system

The Plaxis 2D finite element software is used to analyze the deformation laws of new pile-soil-support system with HS model based on a foundation pit in Shanghai. Contrastive analysis is conducted between finite element and measured values. The results show that the Plaxis 2D can predict the deformation of the new pile-soil-support system. The existence of steel tube inclined brace changes the deformation laws of the traditional double- row piles and can reduce the displacement of top of the double-row piles effectively. The deformation of retaining piles of the new pile-soil-support system satisfies the safety and deformation requirements of the foundation pit. The new support system has no inner supports and it avoids a lot of construction waste generated by the construction and demolition of temporary supports. It is safe, economy and green environmental protection, and it can provide reference for the deep and large foundation pits in soft soil areas.

Experiment study of vibration isolation by multi-rows of piles

Pile barriers have been broadly used to decrease the effect of ground vibration generated by machines or traffic. However, so far, the research about the model test of vibration isolation of pile barriers is very few. In the present paper, the basic properties of the soil in the concrete model box are determined by the basic properties test of the soil firstly. Secondly, through the model tests with two types of piles under different vibration frequencies, the influences of different factors on the vibration isolation effect of pile barriers are studied. The results show that the multi-row pile barriers can effectively isolate the vibration. The main factors influencing the isolation effect are the pile diameter, the number of rows of piles and the vibration wave frequency.

A successful sustainable engineering project of reutilizing existing row piles in deep foundation pit

A successful sustainable engineering project of reutilizing existing row piles in deep foundation pit

Protecting surface and buried structures from tunnelling using pile walls: a prediction model

When tunnelling poses excessive risks for buildings and buried foundations, a pile row barrier may shield the existing structure from ground movements. This paper presents a three-dimensional linear elastic prediction method to evaluate the protective action of pile walls against surface and subsurface ground movements due to new tunnels, both directly behind the wall as well as within the entire ground. Analyses are carried out to evaluate the vertical and horizontal movements of the ground and the pile wall as the result of soil–pile row interaction. New factors that quantify the wall efficiency in reducing settlements and deflections behind the wall are proposed; the results indicate that the effectiveness of the pile wall at reducing horizontal displacements is limited. Subsequently, predictions are compared against field and numerical data to demonstrate that the elastic solution is applicable, particularly for small ground losses. Finally, the barrier efficiency in reducing settlements is discussed comparing pile walls and diaphragm walls.

Vertical and horizontal displacement of model piles in dry soil with horizontal excitation

A series of laboratory tests was conducted to measure the vertical and horizontal displacement responses of pile foundations when subjected to dynamic loads. Eight tests were conducted on a single pile in dry soil at a relative density (RD) of 30% (loose) or 50% (medium); 66 tests on groups of piles with different spacings and patterns in dry soil at RD 30% and 50% were also performed. All the tests were carried out at operating frequencies of 0.5, 1 and 2 Hz under horizontal shaking and all considered one embedment ratio (L/d = 30). The tests were grouped in terms of the number of piles (two, three and four piles in row and line patterns) and three pile spacing ratios (s/d = 3, 4 and 5). The vibration box used in this work was able to simulate accurately earthquake motion induced on foundations and pile groups. An increase in shaking frequency led to a reduction in the oscillation of wave propagation values recorded due to densification of the soil during shaking. The pile spacing was found to be an important parameter that affects the time–frequency characteristics of displacement at the pile top. With an increasing in the pile spacing ratio s/d, the internal forces were slightly reduced.

A laboratory and field-monitoring experiment on the ability of anti-slide piles to prevent buckling failures in bedding slopes

Buckling failure is a special form of a landslide, and it has been little debated in the literature so far. There have been few studies conducted on this type of slope failure, and the corresponding reinforcement measure research has also been rarely conducted. Therefore, it is nearly impossible to provide systematic guidance for the reinforcement and monitoring of such a slope. In this study, a new type of slope test system is developed, and the reinforcement effect of double-row piles was studied using simplified laboratory tests. Under the conditions of no pile and piles, load tests on the sliding body were carried out, and the ultimate loads that can be borne by the slope sliding body under these two conditions were analyzed. The multivariate information evolution of stress, displacement, and pile deformation under these two conditions were studied using multiple monitoring methods. The results showed that anti-slide piles can significantly improve the ability of the sliding body to withstand external loads. For the condition of no piles, 4 kN/m (20.55 kPa) was the critical value and the critical load the slope could bear reached 10 kN/m (51.38 kPa) after the installation of piles. The first row of piles withstood more load than the second row of piles, and double-row pile reinforcement can effectively improve the anti-slip safety reserve. In addition, monitoring of the deformation of the slope and anti-sliding piles should focus on the position of the sliding body and the slip face. Based on the results of laboratory tests, on-site field monitoring was then conducted on the target slope, including displacement monitoring at different positions on the slope before and after anti-slide pile construction, deformation monitoring of anti-slide piles, and rock stress monitoring around anti-slide piles. Monitoring results showed that the slope deformation and rock mass stress tended to be stable after anti-sliding pile construction, and the anti-slide piles were conducive to a safe state. The results of this study provide a useful reference for the reinforcement and monitoring of buckling failure in an actual slope.

Study on the influence of bank slope soil deformation on wharf structure

After a large-scale construction period, there are a large number of old high piled wharfs in China’s ports. The pile cap piles and beam members of some wharfs close to the earth retaining structure appear obvious dislocation, and some of them are increasing year by year. In this paper, the typical section of Tianjin Port 16 ∼ 18 wharf is taken as the research object, and a three-dimensional mathematical model is established to simulate the deformation trend of wharf structure with bank slope soil under unbalanced load condition. The results show that the pile cap plays a positive role in the stability of the wharf slope. Partial load can cause the deformation of soil along the bank. The horizontal earth pressure acting on several rows of piles behind the pile cap is large, which leads to large deformation and internal force of the pile body. When the force between the pile top and the beam exceeds the lap strength between them, the pile top and beam will be staggered. The fundamental method to avoid or improve the seaward movement of high piled wharf and bank slope is to block or reduce the horizontal earth pressure from the rear storage area to the front. The scheme of sheet pile wall or bored pile can be selected according to the actual situation.

Investigation of the end bearing load in pile group model in dry soil under horizontal excitation

A series of 94 laboratory tests were conducted to measure the response of pile foundation when subjected to dynamic loads. Eight tests were conducted on single pile in dry soil at relative density 30 % (loose) and 50 % (medium); 66 tests on group of piles with different spacings and patterns. All tests were carried out under operating frequencies 0.5, 1 and 2 Hz under horizontal shaking. All tests were achieved with one embedment ratio (L/d = 30). These tests were grouped in three different numbers of piles; 2 piles in row and line patterns, 3 piles and 4 piles; and three pile spacing ratios (s/d = 3, 4 and 5). The results of dry soil indicating the mechanism of dynamic response of piles and soil subjected to dynamic horizontal shaking include the variation and distribution of acceleration with time in different states of soil in addition to the vertical and horizontal displacements, end-bearing load, peak acceleration and the peak velocity of foundation. It was concluded that for a dry soil bed, the acceleration amplitudes increase with frequency for both soil relative densities (loose and medium) and different pile patterns (number; single or group and different spacing ratios s/d). The maximum acceleration in the foundation is lower than in the soil bed for all operating shaking frequencies, pile spacing ratios and soil states. The decreasing of the maximum acceleration recorded in the foundation as compared to that in the soil bed is between 10-100 % for loose and medium state of soil, and the decrease in loose state is more than in medium state. This means that there is damping effect or attenuation of vibration waves. The amplitudes of recorded acceleration in the pile cap are much higher than in the soil bed for single pile and pile group with different pile spacing ratios, also these amplitudes are increasing with increase of shaking frequency and relative density of the soil.

Comparative effects of adjacent loaded pile row on existing tunnel by 2D and 3D simulation models

Selecting suitable simulation methods for complex problems requires a careful balance between the predicted accuracy and computational effort. This research comparatively investigated the effects of adjacent loaded pile row on an existing tunnel in terms of tunnel deformation and lining force, displacement of soil surrounding between tunnel and pile and load transfer of the pile. Simulations were carried out by eight simulation models consisting of 3D finite element (FE) full models (model 1-2); 3D FE symmetry models (model 3-4); and a pile wall in 2D FE models (models 5-8). In loaded pile row simulation, simulations were performed with two pile types: volume pile and embedded pile. In 2D simulation, the 3D pile row was converted into 2D pile wall under plane strain condition by using three transformation methods. The results show that the predicted tunnel responses are adequately accurate as long as the reasonable soil movement behavior can be reproduced. The 2D equivalent dimensions and 2D equivalent axial rigidity are recommended since they provide conservative estimation on both tunnel deformation and lining forces. The 2D equivalent flexural rigidity is not recommended if the pile response is also of concern. The novelty of this research lies in the use and discussion on the applicability of various 2D and 3D models to simulate the effects of adjacent loaded pile row on the existing tunnel, as opposed to previous studies which focused on one or two simulation models.

Small scale model test on lateral behaviors of pile group in loose silica sand

The accurate predictions of load- deflection response of the pile group are necessary for a safe and economical design. The behavior of piles under the lateral load embedded in soil, is typically analyzed using the Winkler nonlinear springs method. In this method, the soil-pile interaction is modeled by nonlinear p-y curves in a way that the single pile p-y curve is modified using a p-multiplier (Pm) for each row of piles in the group. The average Pm is called the group reduction factor. The Pm factor depends upon the configuration of pile group and the pile spacing (S). The present study was conducted to investigate the effects of various parameters, such as the pile spacing in the group, different layouts and the lateral load angle (Ѳ) change as a new parameter on the Pm factor and group efficiency based on the 1-g model test. The Pm factor is well comparable with the results of the full-scale test on pile group. However, based on the results, the calculated values of the Pm factor for 3×3 pile groups under 2.5-diameter spacing was estimated about 0.38 and under 3.5-diameter spacing was estimated about 0.52, so the calculated values at S/D=3, obtained from interpolation the values of group reduction factor at S/D=2.5 and S/D=3.5, are close to the AASHTO recommendation.

Foundation Pit Support Structure under Special Geotechnical Structure

Due to The Vast Territory of China, The Topography, Geological Conditions and Surrounding Environment of the Construction Project are Very Different. The Design and Construction of the Foundation Pit Support Project is One of the Most Closely Integrated Engineering Measures Combined with the Above Conditions. The Design and Construction of Deep Foundation Pit Support Engineering in Special Geotechnical Areas Has Become One of the Most Complicated Technical Problems in the Field of Civil Engineering Construction. Based on the Above Background, The Purpose of this Paper is to Study the Foundation Pit Support Structure Under Special Geotechnical Structure. This Paper Compares and Analyzes the Materials and Structure Types that Can be Used for Foundation Pit Support, And Concludes that Bamboo is an Economical and Environmentally Friendly New Material, Its Output Large, Good Mechanical Properties, Can Be Used For Temporary Support of Shallow Foundation Pits. It is Proposed to Use the Bamboo Tube as the Foundation Pit Support Material, And it is Applied in the Soft Soil Layer Foundation Pit Support Project in the form of Row Pile Support Structure. In this Paper, the Top Displacement of the Bamboo Pipe Pile is Larger than that of the Steel Pipe Pile, But the Maximum Pile Top Displacement of the Bamboo Pipe Pile is 1.8mm. The Maximum Displacement of the Pile Top is 18mm, The Displacement is Small, Within the Allowable Range, and in the Actual Project, the Pile Top is Generally Constrained to Further Control the Displacement of the Pile Top to Ensure the Safety and Stability of the Foundation Pit.

Application of multiple combination retaining structures on high slope

With the increase of the height of the filled slope, the application of multiple combination retaining structures (MCRS) is becoming more and more popular. However, the traditional design methods seldom consider the coupling effects between the substructures. To investigate the interaction of MCRS, this paper takes the filled slope project of a middle school in Quanzhou City, Fujian Province, China as an example. The filled slope was supported by MCRS, including reinforced soil, doublerow piles, anchors and counterfort retaining walls. The simulate procedure mainly included the following process: first, the MCRS model was established, then the mechanical response of the MCRS when replacing the fill materials and increasing the length of the rear row piles were obtained, and a comparative analysis was carried out. The following conclusions could be drawn: (1) The properties of backfill material have a significant impact on the displacement of backfill slope, and when the backfill is gravel soil, the displacement of slope can be controlled to a satisfactory degree. When the back-fill soil is replaced by silty clay, the shear strength and internal friction angle of soil become smaller, thus the displacement of slope increases significantly, which may lead to slope failure. (2) When the anchorage length is satisfied, increasing the length of the rear row pile has no significant effect on reducing the displacement of MCRS slope, but it can effectively reduce the axial force of anchor rod. (3) In MCRS, each substructure has complex interaction, and numerical simulation provides an effective means for accurate evaluation of MCRS.

Efficiency of Double Rows of Piles Used As A Breakwater (Dept.C)

The wave transmission, reflection, and energy loss due to closely spaced pile breakwaters consisted of two rows of vertical piles were investigated experimentally. Different parameters were tested such as, the gap-diameter or width ratio, the relative distance between the rows of piles, the wave length, the shape of the piles (square or circular), and the arrangement of the piles (straight or staggered). The square pile breakwater was found to be more efficient than the circular piles in decreasing the transmitted waves. Also, it was concluded that the efficiency of the breakwater was increased as the gap-diameter or width ratio decreased and as the relative span between pile rows increased. Finally, it was noticed that the effect of the pile arrangement (straight or staggered) was slightly affected the breakwater efficiency.