A Review of the Methods Calculating the Horizontal Displacement for Modular Reinforced Soil Retaining Walls

Most of the damage to reinforced retaining walls is caused by excessive deformation; however, there is no calculation method for deformation under static and dynamic loads in the design codes of reinforced soil retaining walls. In this paper, by collecting the measured displacement data from four actual projects, four indoor prototype tests and two indoor model tests under a total of 10 static load conditions, and comparing the calculation results with seven theoretical methods, the results show that the FHWA method is more applicable to the permanent displacement prediction of indoor prototype tests and that the CTI method is more applicable to the permanent displacement prediction of actual projects and indoor model tests. Two yield acceleration calculation methods and four permanent displacement calculation formulas were selected to calculate the displacement response of two reinforced soil test models under seismic loads and compared with the measured values, and the results showed that the Ausilio yield acceleration solution method was better. When the input peak acceleration ranges from 0.1 to 0.6 g, the Richards and Elms upper limit method is used, and when the input peak acceleration is 0.6–1.0 g, the Newmark upper limit method can predict the permanent displacement of the retaining wall more accurately.

Evaluating Lateral Spreading Using Newmark Method Based on Liquefaction Triggering

The prediction of liquefaction-induced lateral spreading is an important geotechnical engineering problem. In this paper, a simplified prediction method based upon Newmark sliding block analysis was proposed to predict the liquefaction-induced lateral spreading. The acceleration time history beneath the liquefied soil (starting from the triggering time of liquefaction) and the postliquefaction yield acceleration corresponding with the residual shear strength of liquefiable soil were used in the Newmark sliding block analysis. One-dimensional effective stress analysis was conducted to obtain the motion beneath the liquefied soil and the liquefaction time. Limit equilibrium analysis was employed to determine the postliquefaction yield acceleration using the residual shear strength of liquefied soil, which correlated with the equivalent clean sand SPT blow count of the liquefied sand. This method was evaluated against five well-documented case histories and the predicted displacements of lateral spreading were subsequently compared with the observed displacements. In addition, the lateral spreading predicted by the rigorous Newmark sliding block method and numerical difference analysis was presented. Based on the statistical analysis of the displacement ratios, it suggested that the method proposed in this paper identified the triggering time of liquefaction and provided a reasonable prediction of the liquefaction-induced lateral spreading with an RMSE (root mean square error) of 0.63, a standard deviation of 0.40, and a CV (coefficient of variance) of 0.60, respectively.

Probabilistic investigation of the seismic displacement of earth slopes under stochastic ground motion: A rotational sliding block analysis

Earthquakes frequently induce landslides and other natural disasters that have a huge impact on human life and properties. In geotechnical engineering, evaluation of the seismic stability of earth slopes has been attracting great research interests. In this regard, the Newmark permanent displacement provides a simple yet effective index of slope co-seismic performance. Traditional Newmark method involves many assumptions and the displacement results thereby calculated are subjected to various degrees of uncertainty. In this paper, a modified rotational sliding block model considering depth-dependent shear strength and dynamic yield acceleration is established. The seismic critical slip surface is analysed through a pseudo-static approach, and the failure volume is larger than that in the static condition. The dynamic yield acceleration is updated by considering the instantaneous movement of the sliding mass in each time-step. The parametric sensitivity of soil shear strength, slope shape and Arias intensity to the permanent displacement is also analysed. The results show that the internal friction angle and the cohesion have equal effects on the permanent displacement. On a logarithmic scale, the displacement approximately linearly correlates with Arias intensity. Furthermore, the underlying uncertainty of the ground motion is introduced to obtain the probabilistic distribution of the seismic slope displacement. The uncertainty of earthquake details has considerable influence on the permanent displacement results.

Evaluating Slope Deformation of Earth Dams Due to Earthquake Shaking Using MARS and GMDH Techniques

Assessing the behavior of earth dams under dynamic loads is one of the most significant problems with the design of such large structures. The purpose of this study is to provide new models for predicting dam dispersion in real earthquake conditions. In the first phase, 103 real cases of deformation in earth dams were collected and analyzed due to earthquakes that occurred over recent years. Using nonlinear and machine learning techniques, i.e., group method of data handling (GMDH) and multivariate adaptive regression splines (MARS), two models for prediction of the slope deformation in earth dams under the various types of earthquakes were applied and developed. The main parameters used in these simulation techniques were earthquake magnitude (Mw), fundamental period ratio (Td/Tp), yield acceleration ratio (ay/amax) as inputs and value of slope deformation (Dave) as output. Finally, in order to check the accuracy of the results of the new models, a comparison was made with the previous relations and models in seismic conditions for the slope deformation in earth dams. The results showed that the MARS model, which is able to provide a mathematical equation, has a better result than the GMDH model. These new models are recommended to be used for future analyses based on their flexible capabilities.