Distribution Of Seismic Earth Pressure Research Articles

Influence of the anchor angle on the seismic response of anchored stabilizing piles: Centrifuge modeling tests

Anchored stabilizing piles (ASPs) are widely used as excavation support systems in slope anti-seismic reinforcement engineering. In this study, a set of centrifuge contrast tests were designed and used to explore the influence of the anchor angle on the seismic response of the system to further deepen the research on the seismic response of ASPs. To this end, the effects of two anchor cable arrangement angles on the slope seismic response, lateral dynamic earth pressure, anchor cable axial force, and pile dynamic moment were compared and analyzed. The results show that changing the angle of anchor cable arrangement can reduce the degree of seismic damage to the slope and the settlement of the slope top (up to a maximum reduction of 77%) and, to some extent, reduce the amplification of acceleration inside the slope. Under seismic action, the different angles of anchor cables do not change the distribution of seismic earth pressure and peak dynamic bending moment but can significantly affect their magnitude and growth rate. The appropriate arrangement angle of the anchor cable can effectively slow the growth of the internal force of the anchor cable and reduce the risk of anchor cable failure. The anchor cable is not the main load-bearing component in an ASP but the primary component that limits pile displacement. Overall, this study can provide a detailed data foundation for subsequent centrifuge comparative tests and parameter analysis.

How do tall buildings affect seismic earth pressures on their basement walls?

The construction of tall buildings has recently undergone exponential growth in major cities, creating new challenges in earthquake engineering and design. For instance, existing analytical procedures for evaluating seismic lateral earth pressures on basement walls connected to these buildings typically ignore the inertia and dynamic properties of the superstructure. The inertial forces from a tall superstructure may cause additional displacements and rotations in its basement, affecting the distribution and magnitude of seismic lateral earth pressures. These additional soil-basement-structure-interaction (SBSI) effects are currently not well understood. Hence, the applicability and reliability of existing procedures to the basements of tall buildings remain questionable. In this paper, we use an experimental-numerical approach to provide insight into how the lateral resisting system of tall superstructures may impact the magnitude and distribution of seismic earth pressures on basement walls buried in dry sand and gravel. Numerical simulations are first validated in 3D using a prior centrifuge experiment that included a simplified model of a 42-story, high-rise structure in medium-dense, dry sand. Then, the numerical tool is used to perform 156 2D, nonlinear simulations of more realistic buildings and basements, ground motion characteristics, and sandy and gravely soil profiles. Nonlinear numerical simulations successfully capture the building's inertial and kinematic seismic interactions with the basement and an adjacent underground structure. The subsequent numerical sensitivity study showed that inertial forces from the dynamic lateral movements of the tall superstructure increase the total lateral earth pressures on the basement walls. This increase is particularly notable in the top two-thirds of the basement wall, and it can be approximated by a trapezoidal distribution. These effects and reliability of existing analytical procedures are shown to be highly sensitive to the building's modal frequencies in relation to the frequency content of the input motion as well as the stiffness of the structure-basement system with regard to the underlying soil. The results highlight the importance of considering the building's dynamic properties and inertia in evaluating seismic earth pressures on basement walls to avoid unsafe estimations or the need for overdesign.

Stability Assessment of Earth Retaining Structures under Static and Seismic Conditions

An accurate estimation of static and seismic earth pressures is extremely important in geotechnical design. The conventional Coulomb’s approach and Mononobe-Okabe’s approach have been widely used in engineering practice. However, the latter approach provides the linear distribution of seismic earth pressure behind a retaining wall in an approximate way. Therefore, the pseudo-dynamic method can be used to compute the distribution of seismic active earth pressure in a more realistic manner. The effect of wall and soil inertia must be considered for the design of a retaining wall under seismic conditions. The method proposed considers the propagation of shear and primary waves through the backfill soil and the retaining wall due to seismic excitation. The crude estimate of finding the approximate seismic acceleration makes the pseudo-static approach often unreliable to adopt in the stability assessment of retaining walls. The predictions of the active earth pressure using Coulomb theory are not consistent with the laboratory results to the development of arching in the backfill soil. A new method is proposed to compute the active earth pressure acting on the backface of a rigid retaining wall undergoing horizontal translation. The predictions of the proposed method are verified against results of laboratory tests as well as the results from other methods proposed in the past.

A centrifuge study of the influence of site response, relative stiffness, and kinematic constraints on the seismic performance of buried reservoir structures

The seismic performance of underground reservoir structures depends on the properties of the structure, soil, and ground motion as well as the kinematic constraints imposed on the structure. A series of four centrifuge experiments were performed to evaluate the influence of site response, structural stiffness, base fixity, and excitation frequency on the performance of relatively stiff reservoir structures buried in dry, medium-dense sand. The magnitude of seismic thrust increased and the distribution of seismic earth pressures changed from approximately triangular to parabolic with increasing structural stiffness. Heavier and stiffer structures also experienced increased rocking and reduced flexural deflection. Fixing the base of the structure amplified the magnitude of acceleration, seismic earth pressure, and bending strain compared to tests where the structure was free to translate laterally, settle, or rotate atop a soil layer. The frequency content of transient tilt, acceleration, dynamic thrust, and bending strain measured on the structure was strongly influenced by that of the base motion and site response, but was unaffected by the fundamental frequency of the buried structure (fstructure). None of the available simplified procedures could capture the distribution and magnitude of seismic earth pressures experienced by this class of underground structures. The insight from this experimental study is aimed to help validate analytical and numerical methods used in the seismic design of reservoir structures.

Seismic active earth pressure of cohesive-frictional soil on retaining wall based on a slice analysis method

The M–O (Mononobe–Okabe) theory is used as a standard method to determine the seismic earth pressure. However, the M–O theory does not consider the influence of soil cohesion, and it cannot determine the nonlinear distribution of the seismic earth pressure. This paper presents a general solution for the nonlinear distribution of the seismic active earth pressure of cohesive-frictional soil using the slice analysis method. A new method is proposed to determine the critical failure angle of the backfill wedge under complex conditions, and an iterative calculation method is presented to determine the tension crack depth of the seismic active earth pressure. The considered parameters in the proposed method include the horizontal and vertical seismic coefficients, wall inclination angle, backfill inclination angle, soil friction angle, wall friction angle, soil cohesion, wall adhesion and uniform surcharge. The classical methods of the M–O and Rankine theories can be regarded as special cases of the proposed method. Furthermore, the proposed method is compared with the test results and previously existing solutions to validate the correctness of the results. Additionally, the parameters׳ effect on the critical failure angle, the resultant force, the application-point position, the tension crack depth and the nonlinear distribution of seismic active earth pressure are studied in graphical form.

Pseudo-dynamic approach of seismic earth pressure behind cantilever retaining wall with inclined backfill surface

Knowledge of seismic earth pressure against rigid retaining wall is very important. Mononobe-Okabe method is commonly used, which considers pseudo-static approach. In this paper, the pseudo-dynamic method is used to compute the distribution of seismic earth pressure on a rigid cantilever retaining wall supporting dry cohesionless backfill. Planar rupture surface is considered in the analysis. Effect of various parameters like wall friction angle, soil friction angle, shear wave velocity, primary wave velocity, horizontal and vertical seismic accelerations on seismic earth pressure have been studied. Results are presented in terms of tabular and graphical non-dimensional form.

Estimation of Seismic Earth Pressures Against Rigid Retaining Structures with Rotation Mode

The evaluation of seismic earth pressures is of vital importance for the earthquake resistant design of various retaining walls and infrastructures. It is one of the key research subjects in soil mechanics and geotechnical engineering. In engineering practices, the magnitude and distribution of seismic earth pressures are greatly affected by the mode and amount of wall displacement. However, classic Mononobe-Okabe solution can only compute the seismic earth pressures at the limit state and doesn’t consider the effect of the mode and amount of wall movement on the seismic earth pressure. In this paper, the formation mechanism of earth pressures against rigid retaining wall with RTT and RBT mode is revealed based on the previous studies and a new method is proposed to calculate the seismic earth pressures in such conditions. Corresponding formula are derived and computer code is written to calculate the seismic earth pressure distribution based on the proposed methodology. Variation of seismic earth pressure coefficient for the rigid retaining wall with RTT and RBT mode is calculated and discussed. In addition, the effectiveness of the method is confirmed by the experimental results.

EFFECTS OF BODY WAVES AND SOIL AMPLIFICATION ON SEISMIC EARTH PRESSURES

To design a retaining wall, conventional Mononobe–Okabe method, which is based on the pseudo-static approach and gives the linear distribution of seismic earth pressures in an approximate way, is used to compute the seismic earth pressures. In this paper, pseudo-dynamic approach is used to compute the seismic earth pressures on a rigid retaining wall by considering the effects of time, phase difference in shear and primary waves and soil amplification along with the horizontal and vertical seismic accelerations and other soil properties. Design value of the seismic active earth pressure coefficient is found to increase with increase in the seismic accelerations, phase difference in body waves and soil amplification, whereas the reverse trend is observed for the passive case. Influence of various soil parameters on seismic passive earth pressure is more significant than that for the active case under harmonic seismic loading. Results are provided in the combined tabular and graphical non-dimensional form for both the seismic active and passive earth pressures. Present results are compared with the available results in literature to validate the proposed non-linearity of seismic earth pressure distribution.

Pseudo-dynamic approach of seismic active earth pressure behind retaining wall

Knowledge of seismic active earth pressure behind rigid retaining wall is very important in the design of retaining wall in earthquake prone region. Commonly used Mononobe-Okabe method considers pseudo-static approach, which gives the linear distribution of seismic earth pressure in an approximate way. In this paper, the pseudo-dynamic method is used to compute the distribution of seismic active earth pressure on a rigid retaining wall supporting cohesionless backfill in more realistic manner by considering time and phase difference within the backfill. Planar rupture surface is considered in the analysis. Effects of a wide range of parameters like wall friction angle, soil friction angle, shear wave velocity, primary wave velocity and horizontal and vertical seismic accelerations on seismic active earth pressure have been studied. Results are provided in tabular and graphical non-dimensional form with a comparison to pseudo-static method to highlight the realistic non-linearity of seismic active earth pressures distribution.

CALCULATION OF SEISMIC EARTH PRESSURE ACTING ON QUAY WALL

Mononobe-Okabe's equation has been proposed in 1924 and has been used for the aseismic design of the retaining wall, today. But it is well known that the effect of cohesion is not considered in this equation.Author measured a resultant force and a distribution of seismic earth pressure acted on a movable model wall, using a shaking table test. Sand used in the tests is slightly cohesive. The test results were discussed by the comparison with the theoretical results proposed by S. OHARA in 1960.Also, we try to verify the base sliding of the gravity type quay walls which were occured during the earthquakes by our theoretical results.