Pile tunnel interaction: literature review and data analysis

The underground space of densely populated cities contains deep foundations and tunnels. Considering the possibility that a new tunnel can be built close to existing piles it is necessary to assess the possible effects of that interaction. Most case studies have shown limited damage on pile supported structures; however, these constructions deal with great uncertainty as the mechanism of pile tunnel interaction is not completely understood. Physical tests at full and reduced scale are a valuable tool to improve that understanding and validate prediction methods. A descriptive review of studies on that matter is presented followed by a quantitative comparison of the results of tunnelling induced axial forces and settlements on the piles. Gathering and analysing these data provided a deeper understanding of the influencing geometrical and structural parameters as well as indicating where further research is needed

Model tests on single batter piles subjected to lateral soil movement

A series of laboratory tests have been carried out to investigate the lateral response of battered piles under lateral soil movement. Model tests were carried out using instrumented rigid aluminium piles. The piles were embedded in homogeneous sand soil at batter angles &beta = 0°, ±10° and ±20° were subjected to two types of lateral soil movement profile. The results obtained from the study are presented in terms of the bending moment, shear force, soil reaction, pile rotation and lateral deflections along the length of the batter pile. The results of model tests on single vertical and batter piles under horizontal loads showed that the batter angle (&beta) significantly influenced the response of the batter piles. Regardless of the value of sand density, bending moment and deflection with batter angles &beta = +10° or positive batter piles were higher compared then vertical piles and negative batter piles

Numerical study of the 3D failure envelope of a single pile in sand

International audienceThe paper presents a comprehensive study of the failure envelope (or capacity diagram) of a single elastic pile in sand. The behavior of a pile subjected to different load combinations is simulated using a large number of finite element numerical calculations. The sand is modeled using a constitutive law based on hypoplasticity. In order to find the failure envelope in the three-dimensional space (i.e. horizontal force H, bending moment M and vertical force V), the radial displacement method and swipe tests are numerically performed. It is found that with increasing vertical load the horizontal bearing capacity of the pile decreases. Furthermore, the presence of bending moment on the pile head significantly influences the horizontal bearing capacity and the capacity diagram in the H-M plane manifests an inclined elliptical shape. An analytical equation providing good agreement with the 3D numerical results is finally proposed. The formula is useful for design purposes and the development of simplified modeling numerical strategies such as macro-element

Investigation into the effect of uncertainty of CPT-based soil type estimation on the accuracy of CPT-based pile bearing capacity analysis

Cone Penetration Test (CPT or CPTu) is commonly used for estimating soil types and also for the geotechnical design of pile foundation. However, the level of agreement between the CPT-based soil types and the traditional identification of soil types based on samples may vary significantly; and it is not clearly understood if this variation has any sort of relationship with the CPT-based pile design. To investigate into this area, a ground investigation trial was carried out at six different locations as part of a highway scheme in East of England. At each location the trial comprised one CPTu adjacent to one borehole (BH) with conventional sampling and laboratory testing. The soil types were estimated from the CPTs and compared with the boreholes findings, and the levels of correlation between them were established. Similarly, the ultimate bearing capacity of a typical bored pile based on the CPTs and on the BHs were calculated and compared. Despite the variable level of disagreement of the CPT-based soil type estimation with the BHs findings, the pile capacity based on CPT data was found to be generally consistent with the values obtained from the traditional BHs-based pile design

Assessment of Helical Anchors Bearing Capacity for Offshore Aquaculture Applications

Aquaculture in Maine is an important industry with expected growth in the coming years to provide food in an ecological and environmentally sustainable way. Accommodating such growth, farmers need more reliable engineering solutions, such as improving their anchoring systems. Current anchoring methods include deadweights (concrete blocks) or drag embedment anchors, which are of relatively simple construction and installation. However, in the challenge of accommodating larger loads, farmers have used larger sizes of the current anchors rising safety issues and costs during installation and decommissioning. Helical anchors are a foundation type extensively used onshore with the potential of adjusting the aquaculture growth demand, though research understanding their lateral and inclined capacity needs to be performed first. This study addresses such topic by performing 3D finite element simulations of helical anchors and studies their reliability for offshore aquaculture farming. Results obtained in this research indicate that the helical anchors capacity could be related to either pure vertical or horizontal resistances, depending on the load inclination angle. Reliability evaluation of helical anchors for inclined loading demand from an oyster aquaculture farm using the Hasoferd-Lind method, indicated these anchors are feasible for operational aquaculture loads

Failure envelopes of pile groups under inclined and eccentric load

A novel numerical procedure for defining failure envelopes of pile groups under inclined and eccentric load is proposed. The starting point is a closed-form exact solution for interaction diagram of pile groups under combined axial-moment loading recently published in the literature. Failure envelopes in the generalised force space are then derived as an extension of this solution by means of an incremental algorithm. It is shown that the axial load at foundation level has always a beneficial effect on the lateral capacity of the pile group, even if this favourable effect is often neglected in practice. On the contrary, the amount of interaction between the horizontal and moment components of the resultant action at failure is usually very small, with the exception of piles groups with end-bearing piles. Some example applications of the proposed method are provided and a simple, yet reliable procedure for ultimate limit-state analysis of pile groups subjected to inclined and eccentric loads is suggested

Soil Reinforcement Model Test Using Timber Pile at Liquefaction Area

Indonesia is a tropical country threatened by many disasters, such as earthquakes and other collateral hazards (liquefaction). Utilization of micro pile on the liquefaction prone areas is quite popular to increase the soil bearing capacity. In this research, Eucalyptus Pellita Timber was used as micro-piles alternatives. This study aims to determine the effect of timber pile addition on soil settlement and the increase in bearing capacity. Some laboratory investigations were conducted, such as timber and soil physical and mechanical characteristics, preloading tests, and seismic load tests by using small-scale shaking table test. The preloading tests were carried out for 40 days, and the settlements were recorded every 24 hours. Subsequently, seismic load tests were conducted on sandy soil with Dr = 40%. The seismic duration was 37 seconds, with PGA = 0.3 g and f = 0.78 Hz. The preloading test results show that Eucalyptus pellita timber piles are able to reduce the settlement by 18%. and from seismic load testing results are able to reduce the settlement by 68% due to earthquake loads with PGA = 0.3g and a frequency of 0.78 Hz on sandy soil with the potential for liquefaction. This is due to the resistance at the tip of the pile and the skin friction on the timber pile. So, from the results of the model test, it shows that the use of Eucalyptus Pelita timber piles can be used as an alternative to handling sandy soils in areas where liquefaction has the potential to occur. Doi: 10.28991/CEJ-2023-09-06-016 Full Text: PD

Failure envelopes of pile groups under combined axial-moment loading: Theoretical background and experimental evidence

The problem of failure envelopes of pile groups subjected to vertical and eccentric load is investigated both theoretically and experimentally. A critical review of literature works on failure envelopes for pile groups under combined axial-moment loading is first provided. Emphasis is placed on a recent, exact solution derived from theorems of limit analysis by idealizing piles as uniaxial rigid-perfectly plastic elements. The application of the relevant equations over a practical range of problems needs only the axial capacities in compression and uplift of the isolated piles. An intense program of centrifuge experiments carried out along with different load paths on annular shaped pile groups aimed at validating the equations pertinent to the above solution is presented and discussed. The endpoints of the load paths followed in the centrifuge lie approximately above the analytical failure envelope, giving confidence that the reference equations can be reliably adopted to assess the capacity of a pile group under combined axial-moment loading. Finally, the kinematics of the collapse mechanism observed experimentally is compared to that determined from the application of the reference theory

Failure envelopes of pile groups under combined axial-moment loading: Theoretical background and experimental evidence

Abstract The problem of failure envelopes of pile groups subjected to vertical and eccentric load is investigated both theoretically and experimentally. A critical review of literature works on failure envelopes for pile groups under combined axial-moment loading is first provided. Emphasis is placed on a recent, exact solution derived from theorems of limit analysis by idealizing piles as uniaxial rigid-perfectly plastic elements. The application of the relevant equations over a practical range of problems needs only the axial capacities in compression and uplift of the isolated piles. An intense program of centrifuge experiments carried out along with different load paths on annular shaped pile groups aimed at validating the equations pertinent to the above solution is presented and discussed. The endpoints of the load paths followed in the centrifuge lie approximately above the analytical failure envelope, giving confidence that the reference equations can be reliably adopted to assess the capacity of a pile group under combined axial-moment loading. Finally, the kinematics of the collapse mechanism observed experimentally is compared to that determined from the application of the reference theory

Equations Used to Calculate Vertical Bearing Capacity of Driven Piles with Shaft Broadenings

In a pile foundation setting practice driven piles with an unconventional (variable) longitudinal shape of surface are widely used. Such piles are made with various slopes of the side faces, may have different types of broadenings, thickenings, etc. The effectiveness of such piles is due to their design features, allowing full use of the natural bearing capacity of the soil base without additional reinforcement. The obvious advantages of these piles make it relevant to study the features of their interaction with the soil stratum, especially the bearing capacity of piles. This study was aimed to investigate vertical bearing capacity of driven reinforced concrete piles with several broadening of the shaft. Numerical calculations and experimental studies of the bearing capacity of piles with broadening under the static loading have been carried out. Equations for calculating the bearing capacity of piles with broadenings are proposed and their verification is performed. The equations include a coefficient that takes into account the features of soil behavior underneath of the pile broadening during palification. Correlation dependence is presented which makes it possible to determine the values of that coefficient depending on the number of pile broadening and the liquidity index of soil. A correlation that makes allow calculations the bearing capacity of piles with broadening via the bearing capacity of a prismatic pile is proposed. The equations are recommended to be used at the stage of variant design of piles with broadening as part of the pile foundations of buildings and structures