RESULTS OF VIBRATION MONITORING OF VIBRO-DRIVING AND VIBRO-EXTRACTION OF SHEET PILES

The geology of St. Petersburg is represented with a heavy layer of weak structurally unstable soils. Using of vibro-extraction and vibro-driving of sheet piles in such conditions requires a particularly responsible approach in order to predict the emerging dynamic effects and the zones of their influence on the surrounding buildings and structures. Therefore, the task of looking for possible patterns describing these processes is highly relevant. For this purpose, the authors have updated the map of engineering-geological zoning according to Zavarzin with use of more than 50 reports of engineering-geological surveys. On this map the sensitive to the high-frequency vibrations soil layers are identified. Also, more than 70 reports on vibration monitoring of vibration driving and vibration extraction of sheet piles in St. Petersburg have been analyzed. The influence on the value of vibration acceleration of the following factors has been investigated: the geological features of the site, the distance to the source of vibrations, the characteristics of the vibrating hammer (operating frequency, driving force) and sheet pile (length, cross section), the location of measurements (on the ground or on a structural element of the building). The result of the work is the diagrams that clearly show the presence or absence of a relationship between the studied parameters. The absence of dependencies for some of the investigated parameters may be caused by the factors which influence cannot be predicted. These factors are the occurrence of large friction forces in the joints of sheet piles; the presence of lenses of dense soils or boulders during sheet piles driving; violations of the technological process. The zone of the influence of high-frequency dynamic impact was identified as 25 meters, which is in good agreement with the results of in-situ monitoring.

Centrifuge tests on axially loaded tapered piles with different cross-sections under compressive and tensile loading

The compressive behavior of tapered piles, particularly those with circular cross-sections, has been investigated during the last few decades. However, the tensile behavior of such piles has been rarely studied in the literature. In this paper, 12 static axial tests, including six compressive and also six tensile tests, were performed on instrumented piles with uniform and tapered cross-sections by using a geotechnical centrifuge. Three of the piles had correspondingly circular, square and X-shaped uniform cross-sections along their length, while the other three ones were non-uniform (tapered), all of which had the same length and volume. The results are presented in three main forms: the variation of load versus pile head displacement, the distribution of axial force along the pile length, and the distribution of the unit shaft resistance along the pile length. The behavior of tapered piles is compared with that of uniform cross-section piles. The results confirm the superiority of tapered piles over uniform cross-section piles in terms of load-bearing capacity and construction costs under both tensile and compressive loading.

Analysis of the Embankment Settlement on Soft Soil Subgrade with a Cement Mixed Pile

The settlement of the widening of soft soil subgrade highways is typically associated with different treatment positions of cement mixed piles. In order to overcome this, in the current paper we employ the finite element method to simulate and analyze the influence of piles under an existing road slope and under an existing subgrade and new embankment on the settlement characteristics of the subgrade and foundation. In particular, we focus on the influence of the pile length and pile spacing on the subgrade and foundation settlements based on a northern high-speed reconstruction and expansion project. The subgrade and foundation soils in the finite element analysis are considered to be homogeneous, continuous, and isotropic elastoplastic materials. The Mohr–Coulomb ideal elastoplastic constitutive model is implemented as the constitutive soil model. The impact of piles under an existing subgrade and new embankment on the settlement is observed to be more significant than that of piles under the existing road slope. Moreover, the subgrade and foundation settlements increase with the pile spacing under the existing road slope and under the existing subgrade and new embankment. More specifically, an increase of the pile spacing from 200% to 400% of the pile diameter is associated with an increase in the maximum settlement of the foundation surface from 1.76 to 1.85 cm (existing road slope) and from 1.44 to 1.96 cm (existing subgrade and new embankment). In addition, the subgrade and foundation settlements decrease for increasing pile lengths under the existing road slope and under the existing subgrade and new embankment, the pile length increases from 4.7 to 9.2 m, and the maximum foundation surface settlement is reduced from 6.2 to 5.52 cm and from 9.73 to 5.43 cm, respectively. The results can provide reference for future subgrade widening projects.

Assessing the effect of governing parameters of bearing capacity determination of small piled rafts on clay soil

In the present study, a small piled raft foundation has been simulated numerically through PLAXIS 3-D software. The objective of this study was to investigate the effect of governing parameters such as pile length, pile spacing, pile diameter, and number of piles on the settlement and load-bearing behavior of piled raft, so as to achieve the optimum design for small piled raft configurations. An optimized design of a piled raft is defined as a design with allowable center and differential settlements and satisfactory bearing behavior for a given raft geometry and loading. The results indicated that, with increase in pile length, pile spacing, pile diameter, and number of piles, both the center settlement ratio and differential settlement ratio decreased. The load-bearing capacity of piled raft increased with increase in pile length, pile spacing, pile diameter, and number of piles. Furthermore, the percentage load carried by the piles increased as the pile length, pile spacing, pile diameter, and number of piles increased. The bending moment and shear force in corner pile are noted to be more, and they decreased towards the center pile. With increase in pile length, the maximum raft bending moment decreased, whereas the maximum shear force in the raft increased. Further, with increase in pile spacing, pile diameter, and number of piles, the maximum bending moment and maximum shear force in the raft increased. The optimum parameters for the piled raft foundation can be selected efficiently with the consideration of maximum bending moment and maximum shear force while designing the piled raft foundation. Thus, the results of this study can be used as guidelines for achieving optimum design for small piled raft foundation.

Analisa Perhitungan Dimensi Turap Kayu (Panjang Kayu Ditanam Dan Tebal) Sebagai Dinding Penahan Tanah Sementara

At this time, the development of retaining structures continues to be optimized according to the available land use, to deal with current and future landslides. The structure of the retaining wall (Turap) is expected to provide a solution for the handling. Based on the type of material used, several types of sheet pile are known, namely; wood sheet pile, concrete sheet pile and steel sheet pile, and based on the type of construction there are two types, namely; cantilever type and anchor type. Sheet pile made of wood, the function of this material is to retain the soil which is not so high. This is because the wood material will not be able to withstand excessive soil or gravel loads. In a handling, knowing the function or planning for handling avalanches is very important, because by knowing the purpose and function of the plan, it can be easier in the design and planning process. Calculations for the quality and efficiency of handling can be achieved as desired. The purpose of this study was to analyze the planning calculation of the dimensions of the temporary wood sheet pile (length of planted wood and thickness) as a soil barrier that was built to prevent landslides caused by the intensity of rain. From the results of the research that has been carried out, the planning of wooden sheet piles with a width of 1 meter and 2 meters as retaining walls and for soil volume ranges from 20 KN/M3-30 KN/M3 while the height of sheet piles is 1 meter - 4 meters. It was found that the length of the sheet pile planted did not affect changes in the volume of the soil while the thickness of the wood did.

Model Study of a Single Pile With Varied Configuration in Sand

In this experimental work, the influence of pile cross-section with varied configurations on the axial compression load capacity of a single pile and related settlement in sand are investigated. The influence of relative sand density (Dr), the pile length to diameter (L/D) ratios and the pile installation techniques are presented. A testing program comprising seven model steel piles with varied shapes of 20 mm width/diameter was conducted. The tests are performed on model piles with the pile length to diameter ratios of 10 and 30 installed in the three cases of sand modeling as loose, medium dense and dense sand. Results indicated that, the rectangular pile is the optimization cross-sectional under the same pile geometry and soil conditions. Also, the increase of the relative sand density has a significant influence on the ultimate compression pile load. Furthermore, the ultimate axial loads of flexible piles in the case of loose sand using the non-displacement method were found to be increased by 119%, 114%, 143%, 82% 139%, 89% and 100% comparing with the ultimate axial loads of rigid piles for the seven models of closed-ended pipe, open-ended pipe, conical base pipe, square closed-ended, square open-ended, tapered and rectangular piles respectively. While, these percentages were found to be increased by (49%, 37%, 26%, 78%, 35%, 71% and 91%) and (77%, 50%, 13%, 116%, 61%, 89% and 85%) in the cases of medium dense and dense sand respectively. The results also indicated that, piles installed in sand using jacking technique have more resistance compared with piles installed in sand using non-displacement technique.

A New Multi-objective Comprehensive Optimization Model for Design of Anti-slide Piles

Landslides have posed a huge threat to the ecological environment and human society all over the world. As the most conventional reinforcement method, anti-slide piles are widely used in the reinforcement of slopes. Currently, more and more attentions have been paid to the low-cost and high-efficiency optimal design of anti-slide piles. However, limitations in the method of the optimization design for slope reinforced with piles still exist. In this paper, a new multi-objective comprehensive optimization method was proposed for the optimization of the slope reinforced with anti-slide piles. The factor of safety, internal force and deflection of piles were selected as the optimization indexes and the optimization index weight was determined by integrating the subjective and objective weight. The influence of the pile location, pile length and pile spacing on the reinforcement effect was analyzed by the numerical simulation. Through the simulation case analysis, the proposed model had achieved good effects on the optimization design of anti-slide piles, which could effectively reduce the engineering costs. The optimization results showed that the best reinforcement effect for the homogeneous slope could be obtained when the anti-slide piles with the critical pile length and small pile spacing was located in the middle of the slope. This provides a new solution for the optimization design of other types of complex slopes, and has broad application prospects.

Prediction of Change Rate of Settlement for Piled Raft Due to Adjacent Tunneling Using Machine Learning

For tunneling in urban areas, understanding the interaction and behavior of tunnels and the foundation of adjacent structures is very important, and various studies have been conducted. Superstructures in urban areas are designed and constructed with piled rafts, which are more effective than the conventional piled foundation. However, the settlement of a piled raft induced by tunneling mostly focuses on raft settlement. In this study, therefore, raft and pile settlements were obtained through 3D numerical analysis, and the change rate of settlement along the pile length was calculated by linear assumption. Machine learning was utilized to develop prediction models for raft and pile settlement and change rate of settlement along the pile length due to tunneling. In addition, raft settlement in the laboratory model test was used for the verification of the prediction model of raft settlement, derived through machine learning. As a result, the change rate of settlement along the pile length was between 0.64 and −0.71. In addition, among features, horizontal offset pile tunnel had the greatest influence, and pile diameter and number had relatively little influence.

The Prediction of Pile Foundation Buried Depth Based on BP Neural Network Optimized by Quantum Particle Swarm Optimization

Due to the fluctuation of the bearing stratum and the distinct properties of the soil layer, the buried depth of the pile foundation will differ from each other as well. In practical construction, since the designed pile length is not definitely consistent with the actual pile length, masses of piles will be required to be cut off or supplemented, resulting in huge cost waste and potential safety hazards. Accordingly, the prediction of pile foundation buried depth is of great significance in construction engineering. In this paper, a nonlinear model based on coordinates and buried depth of piles was established by the BP neural network to predict the samples to be evaluated, the consequence of which indicated that the BP neural network was easily trapped in local extreme value, and the error reached 31%. Afterwards, the QPSO algorithm was proposed to optimize the weights and thresholds of the BP network, which showed that the minimum error of QPSO-BP was merely 9.4% in predicting the depth of bearing stratum and 2.9% in predicting the buried depth of pile foundation. Besides, this paper compared QPSO-BP with three other robust models referred to as FWA-BP, PSO-BP, and BP by three statistical tests (RMSE, MAE, and MAPE). The accuracy of the QPSO-BP algorithm was the highest, which demonstrated the superiority of QPSO-BP in practical engineering.

Buckling Stability Analysis for Piles in the Slope Foundation Based on Cusp Catastrophe Theory

The aim of this paper is to analyze the buckling stability problem for piles in the slope foundation based on cusp catastrophe theory. Formulation of critical buckling load of piles in the slope foundation is obtained. The influential factors of slope angle, distribution of landslide thrust behind the pile, pile-embedded ratio, pile constraints, pile-side friction, pile-side soil resistance, and pile socketed ratio upon buckling stability characteristic for piles in the slope foundation are examined. The results reveal that when pile diameter remains unchanged, critical buckling load increases with the increase of pile length when pile-embedded ratio reaches 60%. When pile length remains unchanged, critical buckling load increases with the increase of pile diameter. Critical buckling load with the assumption of nonlinear horizontal elastic resistance of pile-side soil in the paper is more close to the value based on horizontal elastic resistance of pile-side soil suggested in the code. When slope angle increases, decreased extent of buckling critical load for piles 30–60 m in length is more obvious than the piles which are 10–30 m in length. Strengthening of pile constraints and increase of pile-embedded ratio and socketed ratio are helpful to pile critical buckling load increase. The influential factors of pile-side friction and landslide thrust behind the pile upon pile critical buckling load are tiny and can be neglected.