The Comparison of Laboratory Tests and Numerical Analysis of Pressure and Tension Bearing Capacities of the New System of Microbulb and Micropile System on Clay in Shiraz, Iran

In recent years, the implementations of Micropiles have been increased extensively in large project constructions due to the unique advantages of this method comparing to concrete piles. The results of numerical analysis and centrifuge tests show that the efficiency and importance of micropiles can be considered as an effective solution. This research is designed to compare the newly designed system of microbulb with micropile applying a numerical modeling with finite element software Plaxis 3D foundation v1.6. We also used the FHWA code for a comparative study between micropiles and microbulbs. Then the effective factors were analyzed in order to decide which method is better between these two methods of micropile and microbulb. The results showed that the new microbulb system is an appropriate solution for improvement of mechanical properties of the soil, increase of bearing capacity and settlement decrease

Pullout behavior of polymeric strip in compacted dry granular soil under cyclic tensile load conditions

Assessment of the reinforcement behavior of soil under cyclic and monotonic loads is of great importance in the safe design of mechanically stabilized earth walls. In this article, the method of conducting a multistage pullout (MSP) test on the polymeric strip (PS) is presented. The post-cyclic behavior of the reinforcement can be evaluated using a large-scale pullout apparatus adopting MSP test and one-stage pullout (OSP) test procedures. This research investigates the effects of various factors including load amplitude, load frequency, number of load cycles and vertical effective stress on the peak apparent coefficient of friction mobilized at the soil-PS interface and the pullout resistance of the PS buried in dry sandy soil. The results illustrate that changing the cyclic tensile load frequency from 0.1 Hz to 0.5 Hz does not affect the pullout resistance. Moreover, the influence of increasing the number of load cycles from 30 to 250 on the peak pullout resistance is negligible. Finally, the effect of increasing the cyclic tensile load amplitude from 20% to 40% on the monotonic pullout resistance can be ignored. The peak apparent coefficient of friction mobilized at the soil-PS interface under monotonic and cyclic load conditions decreases with the increase in vertical effective stress. Keywords: Geosynthetics, Post-cyclic pullout behavior, Interface apparent coefficient of friction, Multistage pullout (MSP) tes

The uplift load capacity of an enlarged base pier embedded in dry sand

The purpose of this research is to determine the capability of (and the factors which affect the performance of) an enlarged base pier in resisting uplift capacity. Experiments were conducted in the reinforced bin box of an enlarged base pier with a shaft diameter ranging from 30 to 50 mm, base diameters between 75 and 150 mm and base angles of a = 30°, a = 45° and a = 60°. Tests were conducted in both loose and dense sand packing. A failure mechanism was studied in a glass box for loose and dense sand packing. A dry sand with a unit weight of ?d = 14.80 kN/m3 and ?d = 17. 0 kN/m3 was achieved for loose and dense packing, respectively. Increasing the bell angle and shaft diameter would result in a decrease of the net uplift capacity and failure displacement. This is due to the reduction in the amount of the sand column above the bell that resists the uplift of the pile. Failure displacements at a constant base diameter generally increased considerably with the increase of the embedment ratio but decreased with the increment of the sand density. It is thus apparent that the shaft diameter, bell diameter and bell angle are geometric factors which, together with the embedment ratio and the sand density, should be taken into account in the design of enlarged base piers

Appraisal of reliable skin friction variation in a bored pile

The design of bored piles in Malaysia is usually based on the results of the standard penetration test. It is important to predict the geotechnical capacity of a designed bored pile through the multilayer soil strata. The back-analysis of a test pile is a reliable means of obtaining the range for the ultimate skin factor (Ksu) and the ultimate end-bearing factor (Kbu). In this research, two case histories of maintained load tests on single bored piles (PTP-1 and 2) under full-scale static load (up to twice designed load) are examined. Measurements are taken using various embedded transducers, including both conventional instrumentation and a state-of-the-art global strain extensometer. The results show the rates of the pile base and pile head load mobilisation with settlement, the variation of the skin friction factors and stresses along the pile, and their proportion in relation to the total pile capacity. The Ksu and Kbu factors for both tested piles are obtained and compared using a conventional vibrating-wire global strain gauge and a global strain extensometer. It is also observed that for the stiff soil layers the skin friction is significant. However, the increase in the applied load increases the proportion carried by the end-bearing

Lateral deflection of piles in a multilayer soil medium. Case study: The Terengganu seaside platform

Vibrations from earthquakes can be felt through structures on the ground. One of the characteristics of soil is that it can absorb vibrations to varying degrees depending on its type and properties. The soil profile and depth of each layer of soil is not the same for every place. Therefore, consideration of soil profile and the depth of each layer is important in structural design, especially for offshore structures. In this article, the lateral deflection of piles constructed in a multilayer soil medium is assessed. The evaluation was performed on the Terengganu seaside platform located approximately 350 km away from the Sumatran seismic zones, the Sumatran subduction and fault zones. To model an earthquake, a recently developed attenuation equation was used, and the effect of the shear wave velocity was investigated, considering the soil profile. The results showed that the effect of the wave reduced as it moved further from the epicentre of the earthquake. The piles experienced complete failure when the magnitude of the earthquake was 8.0, with some loss of pile capacity for a magnitude of 7.5 and below. Considering the effect of shear wave velocity (Vs) of the multilayered strata, and using the new attenuation equation, accurate pile deflections, which were in excellent agreement with previously used methods, were obtained

A systematic review and meta-analysis of artificial neural network application in geotechnical engineering: theory and applications

Artificial neural network (ANN) aimed to simulate the behavior of the nervous system as well as the human brain. Neural network models are mathematical computing systems inspired by the biological neural network in which try to constitute animal brains. ANNs recently extended, presented, and applied by many research scholars in the area of geotechnical engineering. After a comprehensive review of the published studies, there is a shortage of classification of study and research regarding systematic literature review about these approaches. A review of the literature reveals that artificial neural networks is well established in modeling retaining walls deflection, excavation, soil behavior, earth retaining structures, site characterization, pile bearing capacity (both skin friction and end-bearing) prediction, settlement of structures, liquefaction assessment, slope stability, landslide susceptibility mapping, and classification of soils. Therefore, the present study aimed to provide a systematic review of methodologies and applications with recent ANN developments in the subject of geotechnical engineering. Regarding this, a major database of the web of science has been selected. Furthermore, meta-analysis and systematic method which called PRISMA has been used. In this regard, the selected papers were classified according to the technique and method used, the year of publication, the authors, journals and conference names, research objectives, results and findings, and lastly solution and modeling. The outcome of the presented review will contribute to the knowledge of civil and/or geotechnical designers/practitioners in managing information in order to solve most types of geotechnical engineering problems. The methods discussed here help the geotechnical practitioner to be familiar with the limitations and strengths of ANN compared with alternative conventional mathematical modeling methods