Influence of soil pile interaction on seismic behavior in sandy condition

Damages of structures supported by deep foundations due to complete or partial collapse have demonstrated paramount importance of the understanding of Soil-Pile Interaction (SPI). Kinematic interaction is due to the presence of pile foundation in the ground. Several methods are available to determine the kinematic interaction. Among these approaches, the method of Beam on Nonlinear Winkler Foundation (BNWF) is widely used in research practices. In the BNWF method, soil and pile are modeled as nonlinear springs and linear finite elements, respectively. Stiffness coefficient of spring is evaluated based on load-transfer approach, often known as p-y curve method. On the other hand, the pile group and the single pile behavior are usually different owing to the impacts of the pile-to-pile interaction known as shadowing effects. Shadowing effects are the condition where there is an overlapping of the stress zones. The p-y curve of single pile can be used in pile group based on p-multiplier concept. Many investigators have developed p-y curves for sandy and clayey soils. However, these developed curves do not account some parameters such as relative density of sandy soil and side friction. This research has developed a new p-y curve for single pile under lateral loading through a comprehensive experimental investigation on Johor Bahru Sand. A good estimation of soil properties in the laboratory was required to simulate natural soil condition. In this study, sand samples prepared using new Mobile Pluviator designed to achieve of the desired relative densities ranging from 10% to 98%. A series of 12 different configurations of piles groups investigated in loose and dense sandy conditions to evaluate the piles interaction effects. The p-y multiplier factor was determined for the piles in the group based on distribution of load applied among the pile groups. The results of different configurations of pile group showed that the ultimate lateral load increased by 53% in increasing of spacing center-to-center piles (s) from 3D to 6D (D=pile diameter) owing to the reduction of pile group interaction effects that improve the performance of the pile group efficiency. A ratio of s/D more than 6 was large enough to eliminate the effects of pile group interaction. The new p-y curve exhibits a lower initial stiffness compared to the p-y curves from previous researchers. The maximum values of displacement and seismic acceleration of the structure occurred almost at the same time for existing and new p-y curves, but the new p-y curve can determine the seismic behavior under the strong earthquakes more accurate than the existing curves because of the higher ultimate lateral resistance

An Experimental Study on Pile Spacing Effects under Lateral Loading in Sand

Grouped and single pile behavior differs owing to the impacts of the pile-to-pile interaction. Ultimate lateral resistance and lateral subgrade modulus within a pile group are known as the key parameters in the soil-pile interaction phenomenon. In this study, a series of experimental investigation was carried out on single and group pile subjected to monotonic lateral loadings. Experimental investigations were conducted on twelve model pile groups of configurations 1 × 2, 1 × 3, 2 × 2, 3 × 3, and 3 × 2 for embedded length-to-diameter ratio l/d = 32 into loose and dense sand, spacing from 3 to 6 pile diameter, in parallel and series arrangement. The tests were performed in dry sand from Johor Bahru, Malaysia. To reconstruct the sand samples, the new designed apparatus, Mobile Pluviator, was adopted. The ultimate lateral load is increased 53% in increasing of s/d from 3 to 6 owing to effects of sand relative density. An increasing of the number of piles in-group decreases the group efficiency owing to the increasing of overlapped stress zones and active wedges. A ratio of s/d more than 6d is large enough to eliminate the pile-to-pile interaction and the group effects. It may be more in the loose sand

Monitoring results of alborz earth dam during construction

Monitoring is one of the most important controlling factors in all earth structure studies. Monitoring is regarded as an important factor in controlling dam security, comparing real action with predicted planning and making good experience and opportunity for future planning. In this paper, we study the pore water pressure, total pressure and settlement in Alborz earth dam by making comparisons between the data taken from the instrument and back analysis on the model. Alborz dam is located in north of Iran. Alborz reservoir was selected to be built on Babolrod River in the conjunction of Gazo and Chakhani. It is within forty-fivekilometers south-east of Babol and 269 kilometers north-east of Tehran. The crest length and width are 838 and 12 (m), the dam height is 78 (m). All the back analysis are achieved by FLAC software from the beginning to the end of the construction, when the dam height is 50 (m). This instrument datum that is installed on earth dam shows that pore water pressure in the core has a normal approach during construction. When the core earth fill height is 50 (m), its maximum pore water pressure coefficient is about 0.5. It is less than its considered amount (0.6). It is expected that it will reach 0.4 at the end of the dam construction. Upstream and downstream shell and core settlement, achieved by data are in turn, 55, 35, and 48 (cm), placed on the earth dam permissible sections which are 1 to 2 percent of the dam height. Meanwhile, as it had been predicted, at the end of the dam construction, core settlement reached 135 cm. Generally, all of the installed instruments worked properly

Sand samples’ preparation using mobile pluviator

It is important to have a good estimation of soil properties in the laboratory when simulation of natural soil condition is required, especially if the soil profile is subjected to static and dynamic loadings. Soil configuration is one of the most important parameters to maintain when preparing soil samples in large area. In this study, the newly designed Mobile Pluviator adopted the air pluviation method for deposition of sand samples. The apparatus is operated based on the uniformity distribution of sand particles with the terminal velocity concept where a series of shutter porosities are chosen for different sizes of sand particles. The densities of the soil samples were determined based on the correlation between the falling height and the rate of soil discharge of the shutter. Using this apparatus, a wide range of Dr (relative density) ranging from 10 to 98 % can be achieved. The advantage of the Mobile Pluviator is that it can be moved to cover a wider area during the raining process and does not interfere with monitoring instrumentation

THE DEVELOPMENT OF THE DESIGN METHOD OF THE LOW-FLOW RATE STAGE OF THE HIGH-PRESSURE CENTRIFUGAL COMPRESSOR ON THE BASE OF THE MODEL OF THE VISCOUS FLOW OF REAL GAS

The new methods of the design ananlysis of the viscous turbulent flow of the real gas in the channels of the working wheel and in the vaneless diffuser, the model of losses and efficiency have been developed. Performed has been the extensive design-theoretical and experimental analysis of the series of the low flow-rate stages, the complex of programs intended for the engineer designs has been created, the character of influence of the number of parameters on the efficiency of the flow part has been revealed. The mathematical model and the design algorithms of the working process of the low flow rate centrifugal stage have been introducedAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

Effects of soil model on site response analyses

For the past two decades, earthquakes have demonstrated a change in the ground motion characteristics under the site conditions as the site analyses have taken an area of active studies. Non-linearity and equivalent linear methods are the two approaches popular and widely used in the design office. Based on the two methods, a number of computer codes have been developed. A deep soil deposit was analyzed and its properties were used as the input data required in the codes. The shear wave velocity was measured by empirical equation. The results of the two methods were compared. It was shown that the values of the acceleration and the strain determined by both equivalent linear and the nonlinear method were significantly greater

A study on UCS of stabilized peat with natural filler: A computational estimation approach

This study applied two feed-forward type computational methods to estimate the Unconfined Compression Strength (UCS) of stabilized peat soil with natural filler and cement. For this purpose, experimental data was obtained via testing of 271 samples at different natural filler and cement mixture dosages. The input parameters for the developed UCS (output) model were: 1) binder dosage, 2) coefficient of compressibility, 3) filler dosage, and 4) curing time. The model estimated the UCS through two types of feed-forward Artificial Neural Network (ANN) models that were trained with Particle Swarm Optimization (ANN-PSO) and Back Propagation (ANN-BP) learning algorithms. As a means to validate the precision of the model two performance indices i.e., coefficient of correlation (R 2 ) and Mean Square Error (MSE) were examined. Sensitivity analyses was also performed to investigate the influence of each input parameters and their contribution on estimating the output. Overall, the results showed that MSE (PSO) R 2 (BP) ; suggesting that the ANN-PSO model better estimates the UCS compared to ANN-BP. In addition, on the account of sensitivity analysis, it is found that the binder and filler content were the two most influential factors whilst curing period was the least effective factor in predicting UCS

Spatial assessment of landslide risk using two novel integrations of neuro-fuzzy system and metaheuristic approaches; Ardabil Province, Iran

This article addresses the spatial analysis of landslide susceptibility in the Ardabil province of Iran. To this end, two well-known optimization algorithms, namely genetic algorithm (GA) and particle swarm optimization (PSO) are synthesized with an adaptive neuro-fuzzy inference system (ANFIS) to create the ensembles of GA-ANFIS and PSO-ANFIS. Besides, the statistical index (SI) model is also performed to be compared with the mentioned intelligent techniques. Fourteen landslide conditioning factors including elevation, slope aspect, land use, plan curvature, profile curvature, soil type, distance to river, distance to road, distance to fault, rainfall, slope degree, stream power index (SPI), topographic wetness index (TWI), and lithology were considered within the geographic information system (GIS). Out of 253 identified landslides, 177 points (70% of them) were randomly selected and used for the training phase, and the remaining 76 points (30% of them) were used to evaluate the accuracy of the SI, GA-ANFIS, and PSO-ANFIS models. Referring to the calculated area under the receiver operating characteristic curve (AUROC) index, the GA-ANFIS (AUROC = 0.914) and SI (AUROC = 0.821) showed the best performance, respectively in the training and testing phases. Notably, ANFIS-PSO emerged as the faster prediction method compared to the GA-ANFIS. Also, from spatial analysis, it was revealed that around 95%, 87%, and 97% of the training landslides, and 96%, 84%, and 76% of the testing landslides are located in hazardous areas

Foundation size effect on modulus of subgrade reaction on sandy soils

Winkler model is one of the most popular models in determining the modulus of sub grade reaction. In this model the sub grade soil is assumed to behave like infinite number of linear elastic springs. The stiffness of these springs is named as the modulus of sub grade reaction. This modulus is dependent to some parameters like soil type, size, shape, depth and type of foundation. The direct method for estimating the modulus of sub grade reaction is plate load test that is done with 30-100 cm diameter circular plate or equivalent rectangular plate. Afterward, we have to extrapolate the test value for exact foundation. In the practical design procedure, Terzaghi's equation is usually used to determine the modulus of sub grade reaction for actual foundation, but there are some uncertainties in utilizing such equation. In this paper the size effect of foundation on sandy sub grade with use of finite element software (Plaxis) is proposed to investigate the validation of Terzaghi's formula on determination of sub grade reaction modulus. Also the comparison between Vesic's equation, Terzaghi's one and obtained results are presented