Bearing Capacity Of Pile Group Research Articles

Effects of disc overhang diameter on the uplift bearing capacity of new-type concrete expanded-plate pile groups

The disc overhang diameter can significantly affect the uplift bearing capacity of new concrete expanded-plate pile groups, affecting their design and practical applications. Accordingly, this effect was investigated considering the failure laws of the soil surrounding various pile types and groups. Based on the uplift bearing capacities of single and double piles, a finite element simulation was adopted to establish models for the four-, six-, and nine-pile groups. The relationship between the disc overhang diameter and uplift-bearing capacity of each pile group was explored: as the disk overhang diameter increased, the uplift-bearing capacities of the pile groups increased; however, this relationship is nonlinear. The optimal disc overhang diameter was determined as 1.5–1.75 times the pile diameter. For a constant disc overhang diameter, corner piles have a greater uplift bearing capacity than side piles in the six-pile group, and a greater uplift bearing capacity than the side and center piles in the nine-pile group. Thus, the pile-group effect depends on the pile position. The uplift bearing capacity did not increase linearly with the number of piles, and the average uplift bearing capacity of a pile in a pile group was less than that of a single pile. Therefore, the uplift bearing capacity of the pile groups decreased as the number of piles increased. The reliability of the simulation was verified via visual testing of a small-scale half-cut pile model.

Influence of Pile Spacing on the Compressive Bearing Performance of CEP Groups

Pile spacing is an important factor affecting the bearing capacity of concrete expansion pile (CEP) groups. In this study, a pile group was simulated and analyzed using ANSYS software R19.0. The influence of pile spacing on the bearing capacity of the pile group under a vertical load was determined using three sets of four-, six-, and nine-pile models with different pile spacings. The grid division of the pile soil model adopts a mapping method, using the contact types of rigid and flexible bodies and applying surface loads to the model piles step-by-step. After vertical pressure was applied to the model pile, in-depth analysis was conducted on the displacement cloud map, pile top displacement, and other data. The different stress conditions of corner, edge, and center piles in each model group were compared and analyzed, revealing the relationship between the stress mechanism and failure law of the soil around the pile and the pile spacing. It was found that the soil displacement range of edge piles is slightly larger than that of corner piles. This phenomenon gradually decreases with increasing pile spacing. When the pile spacing increases to four times the cantilever diameter, the difference in soil displacement at different pile positions is small, and the pile spacing has little effect on the compressive bearing capacity of the pile group. Thus, it is reasonable to control the pile spacing at three to four times the cantilever diameter. In the nine-pile model, when the load is loaded to the 20-step level, the displacement value of the central pile is −72.278 mm, while the displacement values of the edge pile and corner pile are −69.012 mm and −66.806 mm. It is shown that increasing the pile spacing can effectively reduce the pile group effect and improve the bearing capacity of the pile foundation. At present, CEP pile groups are gradually being applied in practical engineering, but research on the influence of pile spacing on the compressive bearing performance of CEP pile groups is still at a very early stage. This article reinforces the influence of pile spacing on the compressive bearing performance of CEP pile groups. It provides theoretical support for its application in practical engineering.

Analisis Daya Dukung Fondasi Bored Pile Pada Rumah Sakit Sultan Imanuddin Pangkalan Bun

This study intended to analyze the bearing capacity of single bored pile, the bearing capacity of the bored pile group, the load carried, the safety factor, and the settlement that occurs. The first calculation method is Schmertmann and Nottingham method, and the second calculation method is Meyerhof method. Based on the calculation of the bearing capacity of a single bored pile using the Schmertmann and Nottingham method obtained a value Qu = 49005,88 kN, while the Meyerhof method obtained a value Qu = 1633.71 kN. The calculation results for bearing capacity of the pile group using the Schmertmann and Nottingham method obtained a value Qg = 164169,70 kN and the Meyerhof method obtained a value Qg = 5472.93 kN. The results of the load carried by the bored pile group using Schmertmann and Nottingham method is Qi = 353.98 kN ≤ Qg = 164169.70 kN which means it’s still within safe limits. Using the Meyerhof method is Qi = 353.98 kN ≤ Qg = 5472.93 kN which means it is still within safe limits. The safety factor using the Schmertmann and Nottingham method obtained SF = 463.78 and using the Meyerhof method obtained SF = 15.46 which means it is very safe. Total settlement of a single bored pile is S = 0.0142 m ≤ 0.04 m which means it is safe. And the settlement of the bored pile group is Sg = 0.03 m ≤ 0.08 m which also means it is safe

Physical Modeling and Analysis of Cast -In-Situ Reinforced Cement Concrete Piled Raft in Clayey Soil

The combined piled raft foundation (PRF) arrangement has been frequently used for various constructions across the globe such as high-rise buildings, railways and varies structures imposing heavy loads etc. This combined system plays an important role in minimizing the settlement and more importantly the differential settlement without compromising with safety of the structure. However, strategically located piles improve the overall structural performance of the system by minimizing settlement and improving its load carrying capacity. The load carrying capacity of either the pile or the raft is considered in traditional design methods. Number of research papers has revealed that this method is uneconomical. Such design method is correct when soil support below raft may vanish like in offshore structure. The present paper investigates the settlement behavior, structural interaction between pile, soil and the raft and load sharing ratio using series of in-house experiments. For this, tests were conducted on physically modelled reinforced concrete piles and raft embedded in compacted soil under steady static loads with different pile configurations viz., free standing pile, pile group, only raft, pile group without raft and piled raft foundation etc. The results of this analysis show that the pile raft foundation's ultimate bearing capability is significantly higher than the sum of load bearing capacity of pile group without raft and load bearing capacity of individual raft. The innovative design method in which bearing capacity of raft and pile considered is compared with traditional design method where raft capacity is neglected. Then there is increase in load bearing capacity by 175% to 600%. This variation depends on size of raft and number of piles provide. Also the load sharing of between pile and raft dependents upon individual capacities and is self-compensating or self-healing.

Underwater blast response and pile failure analysis of submerged reinforced concrete piles and pile group foundations

This paper presents three-dimensional (3D) nonlinear finite element analyses of pile foundations in saturated sand deposits subjected to submerged explosions. In this contribution, the explosive response and failure analysis of reinforced concrete piled foundations and blast induced wave propagation are investigated. The arbitrary Lagrangian-Eulerian (ALE) analysis tool available in the finite element software LS-DYNA is employed to simulate blast loadings. Parametric sensitivity studies are conducted for pile reinforcement arrangements, explosive charge mass, and the effect of pile head constraint conditions. Also, explosive stress wave propagation in saturated media is investigated. For this purpose, extensive numerical modellings are performed under different explosive charge shape and weights. By adopting suitable material models, the strain-rate-dependent behavior of saturated soil domain, steel reinforcements, concrete piles, and cap piles are simulated. Pile lateral displacements, explosion wave velocity, stress distributions, and pile foundation damages are illustrated in order to study the dynamic response of submerged pile foundations. It has been observed that, the reinforcement arrangement has significant effects on the behavior of the piles subjected to submerged explosions. It was also observed from results that the pile spacing in a pile group affects the bearing capacity of pile groups under explosive conditions. The findings of this research provide valuable information regarding the effects of underwater explosions on submerged piled foundations, guide engineering designers and are considerable for design codes.

A Simplified Calculation Formula for Horizontal Bearing Capacity of Micro-piles Foundation

When m value is above 21, If the horizontal load has not reached the design value of the theoretical ultimate bearing capacity, the foundation pile will first appear bending failure. That is to say, when m value is greater than 21, the horizontal bearing capacity of pile group bearing platform foundation begins to depend on the bending strength of pile itself. The ultimate horizontal bearing capacity of pile group bearing platform foundation in actual engineering has been difficult to reach the ideal design value。 When the value of M is less than 21, the actual horizontal ultimate bearing capacity is consistent with the theoretical calculation, when the m value is greater than 21, the actual horizontal ultimate bearing capacity can be calculated according to the simplified formula proposed in this paper.

Relationship between p-multiplier and force ratio at pile head considering non-linear soil–pile interaction

The p-multiplier concept has been widely used to analyse the response of laterally loaded pile groups. Conventionally, the p-multiplier fm is evaluated iteratively by trial and error comparisons of p–y curves and field measurements. However, these approaches could face numerical difficulties and often require subjective adjustment and therefore could result in non-unique solutions. This paper derives a power relationship between fm and the force ratio at the pile head ηhead, defined by the ratio of the lateral force acting at the head of a group pile to that of a single pile, where ηhead equals fm to the power of n. In the case of long piles, it was found that (a) n = 3/4 when the initial modulus of subgrade reaction kini and the ultimate soil resistance pult are constant with depth; and (b) n = 3/5 when both kini and pult increase linearly with depth. This analytical relationship can then be utilised to determine fm from the test results of group piles and single piles, and quickly estimate the lateral bearing capacity of pile groups.

The piled-raft behavior installed in unsaturated collapsible soils

Pile-raft foundation has been used to increase the bearing capacity of pile group. Most of the studies have been conducted on the pile group, and the effect of pile cap on the bearing capacity is largely neglected. The pile cap system plays an important role in increasing the bearing capacity of the cap group constructed on collapsible soils. In the present study, the collapsibility effect on settlement of pile-raft foundation based on water content and cap rigidity was taken into consideration using experimental procedures. These experiments were carried out on pile-raft, pile group, single flexible cap, and single rigid cap at different water contents. The results revealed that in unsaturated soils, increasing the water content led to decreasing the bearing capacity of the pile-raft system. Furthermore, in the saturation state, the portion of raft effect is negligible and the loads are completely tolerated by piles. The results also showed that decreasing the soil water content increased the efficiency of rigid and flexible cap, pile-raft, and free pile group. Moreover, the efficiency of the rigid pile-raft system is more than that of the flexible system, and the difference is insignificant when the water content reaches to saturation status. Finally, at similar water content and stress, the settlement of the flexible pile-raft system would be greater than that of the rigid pile-raft system.

Bearing capacity of pile groups under vertical eccentric load

The paper deals with the problem of the bearing capacity of pile groups under vertical eccentric load. Widespread practice is to consider the achievement of the axial capacity on the outermost pile as the ultimate limit state of the pile group. However, this approach neglects the ductility of the foundation system and may be thereby overconservative. With the aim of proposing an alternative and more rational approach, a novel formulation for interaction diagrams based on theorems of limit analysis is presented and discussed. The methodology is applicable to the general case of groups of unevenly distributed, dissimilar piles. Piles’ connections to the pile cap are modeled as either hinges or rigid-plastic internal fixities. An application example to a slender structure is also provided, showing that the proposed approach can lead to significant advantages over the traditional design.

Risk Analysis of Vessel-Bridge Collision Based on AASHTO Method

One bridge in the southeast coast was cited as an example and the risk analysis theory was introduced into the study of vessel-bridge collision problem of the bridge. From the survey of the current situation development in the bridge site area and 5000 tons collision-prevention requirements, the annual probability of collapse of the bridge in the year 2020 is over the criterion by the AASHTO model algorithm. In accordance with the AASHTO acceptance criteria for vessel-bridge collision risk, the mentioned vessel collision risk of the bridge was not acceptable. In this paper, based on “m” method and FLAC3D program, the research on horizontal bearing capacity of pile group of one bridge in the southeast coast under vessel impact is performed, and the effects of the anchor is considered, which is significant for the risk analysis and bridge anti-collision study.

Experimental Study on the Interaction Mechanism of Cap—Pile Group—Soil

Static load tests on pile group with prototype size were carried out in order to study the behavior and the working properties of the cap—pile group—soil interaction in the pile group foundation. The soil resistance under the cap, the pile shaft resistance and the tip resistance were measured by installing various measuring gauges. Based on these test results, the cap—pile group—soil interaction characteristics were analyzed. The regulations of the soil reaction on the cap, the shaft resistance and the tip resistance of pile, the mechanism of load transfer have been discussed with comparison to the result of the single pile tests. The bearing capacity of pile group is greater than the sum of the bearing capacity of the single pile obtained from testing in the same site in pile group foundation in the case presented here.

Bearing capacity of pile groups in soils prone to slump-type settlement

Equations for determination of the bearing capacity of pile groups in soils prone to slump-type settlement and the optimal distance between piles in the groups are presented on the basis of solution of the problem of the limiting equilibrium of a single pile using the soil-strength parameters ϕ and c. The results of experimental scientific investigations confirm the computational assumptions made by the author, and also suggest good agreement between computational and field data.

Comprehensive effect coefficients calculating method for lateral bearing capacity of pile groups : Liu, J L Proc Ninth Asian Regional Conference on Soil Mechanics and Foundation Engineering, Bangkok, 9–13 December 1991V1, P247–250. Publ Thailand: Southeast Asian Geotechnical Society, 1991

Comprehensive effect coefficients calculating method for lateral bearing capacity of pile groups : Liu, J L Proc Ninth Asian Regional Conference on Soil Mechanics and Foundation Engineering, Bangkok, 9–13 December 1991V1, P247–250. Publ Thailand: Southeast Asian Geotechnical Society, 1991

Investigation of the bearing capacity of pile groups in clay : Tavares, A X Proc 1st International Conference on Geomechanics in Tropical Lateritic and Saprolitic Soils, Brasilia, 11–14 February 1985V4, P387–393. Publ Sao Paulo: Brasilian Society for Soil Mechanics, 1985

Investigation of the bearing capacity of pile groups in clay : Tavares, A X Proc 1st International Conference on Geomechanics in Tropical Lateritic and Saprolitic Soils, Brasilia, 11–14 February 1985V4, P387–393. Publ Sao Paulo: Brasilian Society for Soil Mechanics, 1985

The bearing capacity of rigid piles and pile groups under inclined loads in layered sand

The ultimate bearing capacity of rigid vertical and batter piles and pile groups in layered sand has been determined under various inclinations of the load varying from the vertical to horizontal directions. The results of load tests on single model piles of different inclinations and on free-standing groups are compared with theoretical estimates. The influence of load inclination on the bearing capacity can be represented by simple interaction relationships between the axial and normal components of the ultimate load. The effect of eccentricity of the load on the ultimate bearing capacity of pile groups is discussed on the basis of previous theory and model test results.

The bearing capacity of rigid piles and pile groups under inclined loads in clay

The ultimate bearing capacity of rigid vertical and batter piles and pile groups in clay has been determined under various inclinations of the load, varying from the vertical to horizontal directions. The results of load tests on single model piles of different lengths and inclinations and on free-standing groups and piled foundations are compared with theoretical estimates. The influence of load inclination on the bearing capacity can be represented by simple interaction relationships between the axial and normal components of the ultimate load. The effect of eccentricity of the load on the ultimate bearing capacity of pile groups is discussed on the basis of previous theory and model test results.

Computer-Based Optimal Design of Sewer Systems

Based on a wide scope of model tests performed in cohesionless soils media, the bearing capacity and efficiency of various pile groups and the action of piles in a group have been considered in detail. The test results have shown that under certain conditions the ultimate load of a group could not be identical with the sum of the bearing capacity of single piles constituting the group, and that action of the pile groups depends in particular on: (1) initial compaction of soil; (2) spacing of piles in a group; and (3) the shape of groups and the number of piles in a group. Some suggestions for calculation of the bearing capacity of pile groups have been presented.