Adjacent Foundations Research Articles

Responses of the ground and adjacent pile to excavation of U-shaped tunnel

Although there are many studies on the impact of tunnel on the surrounding environment, most of them focused on the circular tunnels but very few on U-shaped tunnels. In order to obtain a better understanding of the impact of U-shaped tunnel excavation on the ground and adjacent pile foundations, a simplified analytical method is developed in this work. The U-shaped tunnel is projected into a unit circle using conformal mapping method. The displacement and stress of the soil around the tunnel are solved analyzed. The settlement of a single pile is obtained by the complex variable function and the load transfer method. The influence of grouting is considered in the calculation. The analytical solution is verified by the simulation results given by an equivalent numerical model and validated with the field-measured data in an engineering case in Beijing.

CFG Pile Composite Foundation: Its Engineering Applications and Research Advances

Problematic soils exist almost everywhere on the globe. State-of-the-art solutions to make civil engineering infrastructures built on them are still highly sought. The CFG (cement-fly ash-gravel) pile composite foundation system has been widely used in buildings, highways, railways, and bridge transition sections owing to its proven engineering characteristics in soft ground treatment. This paper discusses about the development and achievements of its engineering applications, along with possible future research directions. The remarkable evolution took place in the past to address projects’ strict differential and postconstruction settlement control requirements including embedding the geosynthetic layer into the load transfer platform and combining it with rigid slabs, as seen implemented in few CFG pile-supported embankments. It was also observed that the interaction of the existing CFG pile composite foundation with an adjacent new foundation pit excavation inevitably presents a complex soil-structure interaction mechanism among the fundamental components—the retaining wall, mat, piles, cushion, and soil.

Influence of transmission tower load under extreme conditions during operation period on the stability of landslide and tower foundation

Taking Yanzi landslide and 500 kV transmission tower foundations on the landslide as the research object, this paper presents a study of the influence of transmission tower on the stability of landslide and tower foundation under extreme conditions during operation period. Firstly, the ultimate loads of transmission tower foundation under different operating conditions are determined. Secondly, based on the limit load of transmission tower, the overall and local stability of Yanzi landslide is analyzed. Finally, the disturbance of tower foundation load state on soil around the tower foundation and the change of tower foundation displacement are studied. The results show that, with the increase of wind speed, the tower foundation load In addition, under the action of wind load, the soil around the adjacent tower foundation basically does not affect each other, the maximum displacement of tower foundation does not exceed 0.5 mm, and the maximum inclination rate of tower foundation meets the requirements of cod.

The contribution of cord rotations to structural response in the near-field

The response of structures with large plan dimensions depends on the wave motion beneath their extended or multiple foundations. In addition to translational components of motion, which are different at the base of each column, or at different points of large foundations, point rotations at the base of individual foundations—as well as cord rotations between adjacent column foundations—all contribute to the overall response. The response contribution from all these components of motion becomes particularly significant in the vicinity of moving faults, in which near-field terms in the wave motion contribute large pulses and large permanent ground displacements. In this work, we examine the relative significance of point and cord rotations in an idealized representation of a structure excited by fault normal pulse dF(t) and fault parallel displacement dN(t).

Curtain grouting experiment in a dam foundation: case study with the main focus on the Lugeon and grout take tests

The Baihetan super-high arch dam is constructed under complicated geological conditions, including large-scale columnar jointed basalt (CJB) with closely spaced joints and multiple interlayer and intralayer shear belts at the lower part of dam base, which may increase a risk of seepage in adjacent dam foundations. Therefore, curtain grouting is used to reduce the permeability of dam foundations. Lugeon and grouting field tests and geological exploration were carried out to investigate curtain grouting characteristics of the dam foundation. The findings were as follows: (1) the permeability coefficient of the first type of CJB and breccia lava without unloading is 2 × 10−5 ~ 5 × 10−5 cm/s; that of the second type of CJB without unloading is 2.5 × 10−5 ~ 5 × 10−5 cm/s; and that of the unloaded third type of massive basalt is 1 × 10−5 ~ 3 × 10−5 cm/s. (2) The rock core shows that the slurry caused repeated splitting of the rock mass and widened the cracks of the rock mass, which resulted in plastic deformation of the rock mass. The P ~ Q curve of the five-point Lugeon test shows that the curve shape is turbulent and that the maximum Lugeon value appears at the highest pressure. (3) The phenomenon of low-permeability conditions with a large grout take can be frequently observed. The proportion of the hole stages with a water permeability less than 1 LU and grout take greater than 50 kg/m ranges from 12.5 to 37.5%. The proportion of holes with permeability greater than 10 Lu and grout take greater than 50 kg/m is 0 to 12.5%. The findings from this case study can provide a reference for engineering construction.

Last man standing: Potential absurdities in the Party Wall etc. Act 1996

This paper analyses the potential absurdities in the Party Wall etc. Act 1996 arising out of a recent party wall case, along with the practical implications for practising party wall surveyors. The Party Wall etc. Act 1996 came into force on 1st July, 1997 and is law in England and Wales. The Act provides a statutory mechanism for resolving disputes where the implementation of ‘notifiable’ works by one property owner (the building owner) has an impact on an adjoining property owner (the adjoining owner). Notifiable works generally comprise adjacent foundation excavations, works to repair, rebuild or modify a shared ‘party’ wall and the construction of walls at, or astride, the ‘line of junction’, being the legal boundary between the lands of two or more owners. In the event a ‘dispute’ arises between the respective property owners over the notifiable works, the Act requires both parties to appoint their own party wall surveyor, whereby the two surveyors then select a third surveyor to adjudicate any dispute they may have. Alternatively, the parties may elect to jointly appoint a single ‘agreed surveyor’ as a neutral arbiter. The agreed surveyor or the three surveyors, as the case may be, then resolve the dispute by way of an ‘award’ which is legally binding unless rendered invalid through procedural defect or where successfully appealed by either party in the county court within 14 days of service.

The effect of spudcan footprints on the vertical bearing capacity of adjacent pile foundations

ABSTRACT It is well recognised that footprints are formed during the spudcan insertion process, which can have a negative impact on adjacent pile foundations.This research presents a simplified three-dimensional finite element model to analyse the effect of footprints on the vertical bearing capacity of adjacent piles in clay. The soil parameters around the footprint were obtained via a comparative analysis of the results yielded by the hole-edge stress theory, a triaxial unloading shear test and an unloading state model test. Based on the simplified three-dimensional finite element model, the skin friction resistance changes of piles under different footprint depths, footprint diameters, and dimensionless distances L/D were calculated. The results showed that the reduction rate of the skin friction resistance of the pile decreases with increasing L/D and increases with increasing footprint diameter and footprint depth. .

Performance of piled raft foundations under the effect of dewatering nearby an open pit

The dewatering arrangement is required in execution works and it needs more attention due to the additional vertical settlement produced on the adjacent pile foundations. Raft foundations are being increasingly utilized for construction in cases of subsoil conditions with a high water table. Also, soil displacements in adjacent un-braced deep open pit may be a reason for high damages to the close buildings and foundations systems. The aim of this study is to examine the behaviour of piled raft foundations considering different pile locations under the effect of line drain and stage drilling of nearby open foundation pit. The line drain was used as dewatering process through the soil in this study. The pile vertical settlement and lateral displacement at various depths of excavation of an open pit in addition to the effect of line drain were investigated. A numerical modelling by using the three dimensional finite element package PLAXIS 3D is presented to simulate the problem. The soil is presumed to consist of two layers of deposit, the first is a clayey layer assuming soft soil criterion and the second is a sandy layer conforming to Mohr-Coulomb failure criterion. It is found that there is an obvious effect of dewatering by line drain with the drilling process for corner and face piles of a piled foundation whereas less effect for the centre piles.

Simple discrete models for dynamic structure-soil-structure interaction analysis

Simple models are presented for dynamic analyses of Structure-Soil-Structure Interaction (SSSI). Structures built on rigid, circular surface foundations resting on a homogeneous, elastic soil half-space are considered. The proposed models consist of discrete mass and spring elements that represent inertial, stiffness, and damping characteristics of an SSSI system. Frequency-dependent springs are developed to simulate Foundation-Soil Interaction (FSI) and Cross-Interaction (CI) between adjacent foundations, both being affected by the number and arrangement of neighbouring foundations. The stated springs are developed using a novel approach that approximates the through-the-soil interaction between adjacent footings using existing solutions to soil-structure interaction (SSI) analyses. Static stiffness matrices are obtained by means of compliance matrices using well known analytical solutions of surface displacement field to a ‘single-disk’ problem and a suggested displacement averaging rule. Dynamic stiffness matrices are created by applying modification factors to their static counterparts. To this end, a practical expression for dynamic modification factors that relate static and dynamic amplitudes of surface displacement field is provided. Equations of motion are formulated and solved in both time and frequency domains, taking into account time-lagging effects on input motion at separate foundations due to their vibration and wave passage. Validation results against more advanced numerical models prove the effectiveness of the proposed models. Finally, the limitations and potential improvements on the models are discussed.

A polynomial mathematical tool for foundation-soil-foundation interaction

This paper studies the dynamic foundation-soil-foundation interaction for two square rigid foundations embedded in a viscoelastic soil layer. The vibrations come from only one rigid foundation placed in the soil layer and subjected to harmonic loads of translation, rocking, and torsion. The required dynamic response of rigid surface foundations constitutes the solution of the wave equations obtained by taking account of the conditions of interaction. The solution is formulated using the frequency domain Boundary Element Method (BEM) in conjunction with the Kausel-Peek Green's s function for a layered stratum, with the aid of the Thin Layer Method (TLM), to study the dynamic interaction between adjacent foundations. This approach allows the establishment of a mathematical model that enables us to determine the dynamic displacements amplitude of adjacent foundations according to their different separations, the depth of the substratum, foundations masss, foundations embedded, and the frequencies of excitation. This paper attempts to introduce an approach based on a polynomial mathematical tool conducted from several results of numerical methods (BEM-TLM) so that practicing civil engineers can evaluation the dynamic foundations displacements more easy.

Active Earth Pressure against Rigid Retaining Walls for Finite Soils in Sloping Condition considering Shear Stress and Soil Arching Effect

The horizontal differential layer element method was used to study the active earth pressure of the finite‐width soil formed by the rigid retaining wall for the embankment or adjacent foundation pits. The cohesionless soil was taken as the research object, and the soil arch theory was introduced based on the translation mode of rigid retaining wall and the linear sliding fracture surface. The minor principal stress line was assumed as circular, considering the deflected principal stress as soil arching effect. The shear stress between level soil layers in the failure wedge was calculated, and the differential level layer method was modified. Then, the theoretical formula of the active earth pressure, the resultant earth pressure, and the point of application of resultant earth pressure were obtained using this revised method. The predictions by the proposed formula were compared with the existing methods combined with the cases. It is shown that the resultant finite pressure increases gradually and approaches to Coulomb active earth pressure values when the soil is infinite, with the increase of the ratios of the backfill width to height. Moreover, the horizontal pressure for limited soils is distributed nonlinearly along the wall height. Considering the shear stress between level soil layers and the soil arching effect, the position of application point of the resultant active earth pressure by the proposed formulation is higher than that of Coulomb’s solution. The wall is rougher, and the resultant pressure will be smaller. The application point distance from the bottom of the wall will increase. Finally, an experiment was conducted to verify the distribution of the active earth pressure for finite soil against rigid retaining wall, and the research results agree well with those of the experimented observations.

Research on Influnence Law of Existing pipe-jacking Tunnel affected by Adjacent Foundation Pit Excavation in Soft Clay Stratum

The problem that existing pipe-jacking tunnel was disturbed by adjacent foundation pit excavation had arose relative researcher’s attention, especially in soft clay stratum. Firstly, by means of numerical simulation, the deformation of diaphragm wall and settlement law of soil outside the pit during foundation pit construction were analyzed. Then deformation and stress characteristics of existing pipe-jacking tunnels were studied influenced by different spacing between foundation pit and pipe-jacking, different excavation depth of foundation pit and different buried depth of pipe-jacking. The main conclusions were as follows. (1) The maximum horizontal displacement of the diaphragm wall was located at 3/4 of the excavation depth of pit. (2) Due to the blocking or isolation effect of existing rigid pipe-jacking on the deformation of surrounding soil, the surface settlement became smaller.(3) Deformation, structural stress of pipe-jacking would gradually decreased under the conditions of increase of the spacing between foundation pit and pipe-jacking, decrease of excavation depth of pit and buried depth of pipe-jacking, (4) Due to the influence of pit excavation, deformation and stress of pipe-jacking near the end wall and middle of the foundation pit were relatively large. (5) When the buried depth of pipe-jacking was located at near 3/4 of excavation depth of pit and the spacing was less than 10m, excavation of the pit has a great impact on the existing pipe-jacking tunnel.

The three-dimensional numerical analysis of the impact of newly Seawall with inner epeirogenic through blowpipe to adjacent pile foundation of bridge

The internal force and deformation of the adjacent bridge pile foundation is influenced by newly Seawall with inner epeirogenic through blowpipe, which may endanger the normal operation of the bridge. Using Plaxis3D software in this paper, the subsoil is used by the Hardening Soil model, and analysis the mechanism of the influence of bridge pile foundation by the newly Seawall with the inner epeirogenic through blowpipe when the distance between Seawall and bridge is changed from 200m to 250m, 300m, 350m and so on, which provides reasonable safety distance between the Seawall and bridge. The analysis results show that the vertical displacement and internal force of bridge pile foundation is less affected by the newly Seawall with the inner epeirogenic through blowpipe, which will not affect the bearing capacity of the bridge pile foundation. However, the horizontal displacement of pile foundation of the bridge is greater influenced by newly Seawall with the inner epeirogenic through blowpipe, which will affect the normal operation of the bridge. As long as reasonable rate is controlled by epeirogenic through blowpipe, the max horizontal displacement of pile foundation can meet the design requirements when the distance is 300m between Seawall and bridge.

Influence of Dewatering in Deep Excavation on Adjacent Pile Considering Water Insulation Effect of Retaining Structures

Dewatering of the foundation pit is an important measure to ensure the safety of the excavation. Accurate prediction of the effect of dewatering on adjacent pile foundations is an important prerequisite for the safety of surrounding buildings. This paper presents a procedure which can consider water insulation effect of retaining structures to estimate the drawdown, the soil consolidation settlement, the negative friction on the pile shaft and the additional pile settlement, induced by dewatering. The well document calculation results are used to examine the efficiency and accuracy of the proposed analytical approach. The good agreement shows that the analytical approach presented in this study displays a satisfied consistence with the existing methods in calculating the settlement of surrounding soil and pile top. The influence factors of the pile settlement are also analyzed.

Evaluating of Bearing Capacity of Two Adjacent Strip Foundations Located around a Soil Slip

Evaluating of Bearing Capacity of Two Adjacent Strip Foundations Located around a Soil Slip

Influence of Foundation Pit Excavation on Structural Safety of Adjacent Existing Tunnels

The existing subway tunnel will be deformed due to the excavation unloading of the adjacent foundation pit, which will affect the normal use and safety performance of the tunnel. Therefore, it is particularly important to evaluate the impact of foundation pit engineering on the structural safety of adjacent subway tunnels. The third phase of Tianjin Yellow River Hospital, with a depth of more than 5m, is close to Tianjin Metro Line 2. The results show that the displacement of soil around foundation pit and subway tunnel segment increases with the excavation process, but is less affected by floor load. In addition, the vertical displacement of subway tunnel segment is mainly affected by foundation pit dewatering, its axial force and bending moment remain stable in the construction process, and the crack checking result is within the allowable range. The results of this paper can provide an effective reference for the project impact assessment.

Effect of Tunneling on Adjacent Piled Foundation in Clay

Soil movements arising from tunnel excavation may induce severe stresses on adjacent piled foundations. This paper investigates the behavior of piles due to nearby tunneling in soft clay using centrifuge modeling technique. Centrifuge modeling has an advantage that the consolidation time of the clay under forced gravity field can be expedited significantly to study the long term performance of a pile due to tunneling. The types of piles investigated in the present study include floating pile, socketed pile and end bearing piles with different pile head conditions. The test results on the induced axial and lateral pile responses due to tunneling are presented in this paper and the implications of the findings to engineering practice are highlighted.

INFLUENCE OF PVD-ENHANCING SOFT SOIL GROUND ON THE ADJACENT BRIDGE PILES – A 3D FEM ANALYSIS


 
 
 The influence of prefabricated vertical drain (PVD)-enhancing soft soil on the adjacent bridge pile foundation is not sufficiently clear. The related studies are scarce and far behind the requirement of engineering practice. Three-dimensional finite element model (3D FEM) is established to investigate this important issue. Plastic drainage boards in the PVD are modelled by a user-defined element, which considers the axial force and permeability of the plastic drainage board, whereas its weight, shear, and torsion are not considered. The elastoplastic-consolidation coupled model is used for the soils. Field measured results of pore water pressure, ground settlement, and pile cap displacement are used to validate the 3D FEM with good accuracy. A number of useful conclusions can provide guidelines for similar projects and inform designers of the adverse effects of PVD-enhancing soft soil ground on the adjacent bridge pile foundation.
 
 

A method for frost jacking prediction of single pile in permafrost

In this paper, a model is proposed to simulate frost jacking performances of a pile foundation within an axisymmetric pile–soil system through a coupling strategy. We consider three diversified stages for frost heave of adjacent foundation soil below freezing point, where mathematical expressions for the volumetric strain are given in terms of volumetric ice content, negative temperature and porosity. A modified strain-softening model characterizing frozen soil–pile interactions is established based on experimental results, taking into account the effects of normal pressure, negative temperature and moisture content. The proposed computational approach is then illuminated and validated via the numerical example of a simplified bridge pile foundation under natural permafrost condition. Variation of temperature regime, volumetric ice content, displacement and stress over time is analyzed. This model can be further applied to evaluating effects of different countermeasures that mitigate frost jacking hazard of single pile subjected to cold climate.

Observed Performance of Two Adjacent and Concurrently Excavated Deep Foundation Pits in Soft Clay

AbstractWhen adjacent foundation pits are excavated concurrently, the stress and deformation of the soil and structures are affected by their interactions. This paper investigates the performance o...