Horizontal Soil Reaction Research Articles

Contribution to the forecast of horizontal displacements in continuous fight auger piles in granular soil profile

This article presents a series of propositions for the prediction of horizontal displacements for continuous fight auger piles in granular soil profiles through modifying the parameters Ay and By from the method proposed by Matlock and Reese (1961). Empirical proposals were also presented for calculating the horizontal soil reaction coefficient (nh) for granular soils. Data from ten horizontal static load tests, conducted in the city of Paulino Neves (State of Maranhão, Brazil) were used to develop and validate the propositions. The data regarding results of nine static load tests (PCH 1 to PCH 9) were used to develop the propositions, whereas results for PCH 10 and other data from other studies (Cases A and B) were used in the validation step. Modifying the parameters used in Matlock and Reese’s method resulted in convergent and coherent predictions for all the propositions assessed in this study. In addition, predictions made for piles used in the validation phase yielded results very congruent with experimental displacements.

Analysis of in situ bridge columns with exposed caisson foundations in a gravel stratum under lateral loading

In this study, three in situ laterally loaded tests on bridge columns with caisson foundations in gravels were numerically explored. The three tests differed in the application position of lateral loads and the exposed length of the foundations. The analysis model used beam–column elements with distributed plastic hinges to simulate the column and a six-component Winkler beam model to simulate the foundation. The lateral stiffness of the foundation with combined moment and horizontal loading and a large exposed length was the smallest. Although the foundations were situated in a gravel stratum, the caisson with a large exposed length underwent significant foundation flexibility and nonlinearity; however, with increasing lateral loading, the influences of foundation flexibility and nonlinearity on the lateral displacement of the columns were reduced because column yielding limited the load transfer to the foundation. The horizontal soil reactions in front of the foundation and the side horizontal shear soil reactions along the caisson shaft provided major resistances to lateral loading (horizontal load and overturning moment). With increasing foundation exposure, the contribution of the base soil reactions increased, but the contribution of the side horizontal soil reactions decreased accordingly. The side vertical shear soil reactions and base normal soil reactions contributed moment resistance to reduce the foundation displacement and rotation and thus promoted the overall lateral capacity of the caisson foundations although they did not provide direct counterbalances to horizontal loads.

General Winkler Model for Kinematic Responses of Shafts in Linear Soil

A simplified model for calculating the seismic responses of the shaft is proposed in this paper. Based on the theory of Winkler elastic foundation beam, the urban shaft is simplified as a vertical beam. The horizontal soil reaction and vertical shear tractions between the shaft circumference and the surrounding soils are considered through horizontal springs and rotating springs on the sidewall of the shaft. The translation and rocking motion of the shaft are considered through horizontal springs and rotating springs at the bottom of the shaft. Then, the dynamic analysis model of the shafts under seismic motion is established, and the control equation of the dynamic response of the shaft in frequency domain is deduced. The analytical solution of the steady state response of the shaft is obtained. Considering the randomness of the earthquake motion, this method can get the shaft kinematic responses under different ground motions efficiently in conceptual design process.

Buried pipelines with bends: analytical verification against permanent ground displacements

Available analytical methodologies for the stress analysis of buried pipelines against large permanent ground displacements (PGDs) apply only to straight pipeline segments. Hence, a new methodology is proposed herein for the analytical computation of pipeline strains in bends of arbitrary angle and radius of curvature, located outside the PGD high-curvature zone, but within the pipeline’s unanchored length. The methodology is based on the equivalent-linear analysis of the bend, assuming that it will perform as an elastic arched beam subjected to uniformly distributed ultimate axial and transverse horizontal soil reactions. The end of the bend towards the PGD zone is subjected to an axial displacement, calculated on the basis of overall displacement compatibility along the pipeline, while the other end is restrained by the unanchored pipeline segment beyond the bend. Using this approach, the maximum axial force at the vicinity of the PGD zone can also be calculated and consequently used for the estimation of corresponding pipeline strains with any of the available numerical or analytical methodologies for straight pipeline segments. Parametric nonlinear finite element analyses are performed to verify the analytical methodology and also derive conclusions of practical interest regarding the effect of bends on pipeline design.

Erratum for “Horizontal Soil Reaction of a Cylindrical Pile Segment with a Soft Zone” by Xenia Karatzia, Panos Papastylianou, and George Mylonakis

Erratum for “Horizontal Soil Reaction of a Cylindrical Pile Segment with a Soft Zone” by Xenia Karatzia, Panos Papastylianou, and George Mylonakis

Horizontal Soil Reaction of a Cylindrical Pile Segment with a Soft Zone

An analytical solution in the realm of two-dimensional linear elasticity theory is presented for the soil reaction around a laterally loaded cylindrical pile segment surrounded by an annular zone of soft elastic material, under plane strain conditions. To this end, a seminal model is extended to account for different boundary conditions at the interfaces separating the annular zone from the pile and the outer material. Analytical closed-form solutions are derived for the stiffness of the system and the stress and strain fields in the annular zone, for the following combinations of shear boundary conditions: (1) perfectly bonded interfaces, (2) perfectly smooth interfaces, (3) perfectly bonded inner and perfectly smooth outer interface, and (4) perfectly smooth inner and perfectly bonded outer interface. It is shown that for both very thin and very thick soft zones, the stiffness of the system becomes independent of shear boundary conditions. The predictions of the model are compared against those of two models based on strength-of-materials theory. Three-dimensional effects and numerical simulation aspects are discussed.

Combined loading of caisson foundations in cohesive soil: Finite element versus Winkler modeling

The undrained response of massive caisson foundations to combined horizontal, vertical and moment loading is parametrically investigated through a series of 3D finite element analyses. The parameters are: (a) the embedment ratio (D/B), (b) the factor of safety against initial vertical loading (FSV) and (c) the ratio of the overturning moment to the horizontal force applied at the top of the caisson (M/Q). Emphasis is given on: (i) the identification of all possible failure mechanisms in M–Q–N space, (ii) the developed stress distributions along the caisson walls for various load levels up to complete failure conditions. The results are then used as a feedback for calibrating the parameters of a generalized four-type spring model, originally proposed by Gerolymos and Gazetas (2006), through a genetic algorithm-based optimization procedure. The predictions of the Winkler model compare very well with the FE results, not only at the local response level (in terms of stress distributions along the caisson shafts), but at a global response level (in terms of force–displacement curves and M–Q–N failure envelopes at the top of the caisson) as well. Contrary to established lateral soil resistance theories, it is shown that both the ultimate horizontal soil reaction and resisting moment per unit depth do not solely depend on the strength properties of soil and geometry of the caisson but are also functions of the applied load ratio M/Q and initial soil yielding due to vertical loading. Interesting conclusions are also drawn regarding the transition from the elastic to the ultimate limit state (hardening). Quantifying through analytical expressions the contribution of each of the two basic lateral resisting mechanisms to the response of the caisson, a classification method for embedded foundations is then proposed. The capabilities of the Winkler model are further demonstrated through comparison with FE analysis of the caisson cyclic lateral response.

Soil Parameter Identification Based on Field Monitoring Value of Displacement and Stress in Pit Retaining Structure

Parameter-M is the proportion factor of horizontal soil reaction when the soil is compressed horizontally, and the corresponding method of pit retaining structure analysis is named as M-method. M-method is widely used to determine the working state of pit retaining structures in China, however, parameter-M varies significantly when deduced by different approaches. An analysis unit is chosen in the subway station pit in Zhengzhou, center of China, on the bank of Yellow River. The retaining structure consists of reinforced concrete piles, internal bracing struts made of steel pipes. The horizontal displacements of retaining piles and the axial forces in pipe bracing struts are monitored in-situ. Then, calculation assumption is taken as that during the elastic deformation stage, parameter-M for each soil keeps constant. Then a series of equilibrium equations of forces acting on retaining structure are set up to determine the values of M for each soil corresponding to deferent stages of excavation. When the identified values of M are applied in the later projects, it shows the validity and accuracy of the method. Precise values of M are applied in the similar geological sites to optimize the retaining structure design.

Effect of Aspect Ratio on Soil Reactions on Flat Tines in Dry Sand

Experiments were conducted in a laboratory soil bin with dry compact sand to study the effect of tine aspect ratio (tine width/tine depth in soil) on soil reactions. The tine was moved in the soil in a quasi-static condition and soil reactions were measured by an L-shaped force transducer. It was observed that vertical and horizontal soil reactions were cyclic in nature and were in phase for all the tines used in this study. Wavelength and amplitude of horizontal soil reaction was found to increase with tine aspect ratio and depth. The fine aspect ratio also affected the magnitude of soil reactions. When the tine aspect ratio was changed from 1 to 2, the horizontal soil reaction increased by 10 kN for a fine operating at 50 mm depth while it increased by about 300 kN for a tine operating at 125 mm depth. The rate of increase of wavelength of the horizontal soil reaction was about 20% for all tines as aspect ratio increased from 1 to 2. The soil reactions changed linearly with aspect ratio at a given depth. The soil reaction changed with tine depth, at a given aspect ratio, showing a cubic parabolic curve.

Effect of Displacement Rate on Horizontal Soil Reaction in Sand

This study concerns the effect of the displacement rate on the relation between the horizontal soil reaction and the displacement of sand touching structural elements such as the side of a foundation, basement wall, etc., in case the relative displacement between the soil and the structure is considerably large. The dynamic horizontal soil reactions acting on structures are considered to be affected by many factors. In the present study, simultaneously taken into consideration, are two factors, the number of loading and the depth below the ground surface, in addition to the displacement rate. In the experiments performed by the authors, an extremely rigid pile buried in three kinds of sands was swayed at displacement rates ranging from about 10 ~ 4 cm/sec to about 10 2 cm/sec. The displacement at the top of the pile and the soil reaction at six points on the pile face, arranged at a depth of 8 cm to 108 cm, were measured.

Ground Vehicle Mobility on Soft Terrain

In order to evaluate soil-vehicle system and to simulate vehicle action for research purposes, tilting plate penetrometer was designed that is capable of measuring, simultaneously, vertical and horizontal soil reactions for given sinkage and horizontal slippage of flat plate; vehicle performance measurements; indexes of performance with respect to trafficability.