On the modeling of frequency- and intensity-dependent impedance functions at the head of horizontally loaded single piles

This paper proposes a phenomenological model that represents both the frequency and intensity dependencies of the dynamic force–displacement relationship at the head of horizontally loaded piles. The present model consists of a bilinear spring unit with hysteretic characteristics and a so-called “Gyro-Lumped Parameter Model (GLPM)” unit arranged in series. The former unit represents the static yielding procedure of soil-pile systems, while the latter represents the frequency-dependent characteristics of impedance functions. Firstly, this study validates the general behavior of the proposed model and then verifies it by simulating the experimentally obtained pile head impedance functions of a single pile for small to large amplitudes of loading in a wide range of frequencies. The results show that the proposed model can sufficiently reproduce variations in the frequency-dependent characteristics of impedance functions for a wide range of loading amplitudes.     

Reliability-based optimization of laterally loaded piles

A general approach to the reliability-based analyses and the optimum designs of laterally loaded piles (LLOP) is presented. This approach takes into consideration all behavior and side constraints specified by standard specifications for piles. Additionally, the casual effect of corrosion of piles with time is considered in formulation with limiting state functions. The solution to reliability-based problems is obtained by a computer program (RELLOP). A general reliability based methodology is developed and implemented in the developed computer program (RELLOP) for both element and system limit states. Numerical examples demonstrating the feasibility of considering multiple limit states and system reliability requirements in the design of laterally loaded piles are presented. Effects on the reliability-based design solution of allowable reliability levels, and time of exposure to corrosion are also illustrated.     

Design of laterally loaded piles in a nonlinearly deformable bed

Conclusions 1. The computational method that we have proposed makes it possible to study the performance of the "pile-soil" system in the elastoplastic stage and investigate the behavior of piles and pile frames in all stages of loading — right up to failure.2. Allowance for shear strains in the cross section enables us to reflect the stress-strain state of the "pile-soil" system more precisely and provide high serviceability to the pile beds.Astrakhan Technical Institute, RPKh. Far East Scientific-Research Institute for the Design and Planning of Marine Structures. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 4, pp. 9–11, July–August, 1980.     

水平搅拌桩技术在浅埋隧道施工中的应用

介绍水平搅拌桩法在软土、浅埋隧道施工中的应用及分析其应用效果。     

Engineering method of analyzing the bearing capacity of horizontally loaded pile groups

An engineering method is presented for analysis of the bearing capacity of a horizontally loaded pile group on the basis of the resistance of a single pile with a free head; the method accounts for the interaction between piles in the foundation, and the rigid fixity of their heads in an undeformable grillage. Results of the analysis performed in accordance with the developed procedure are compared with data derived from field tests of pile foundations. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 7–11, March–April, 2000.     

Analysis and design of axially loaded piles in rock

Despite significant advancements in in situ test techniques, construction practices, understanding of rock joint and rock mass behaviours, and numerical analysis methods, the design of bored concrete cast-insitu piles in rock is still largely based on the assessment of bearing capacity. However, for many of the rock conditions encountered, the bearing capacity of piles is a nebulous concept and a figment of the designer's imagination. Even if it can be reasonably quantified, it has little, if any, significance to the performance of a pile in rock. The load carrying capacity of even low strength rock(in most situations) is far in excess of the strength of the structure(for example, a building column) transmitting the load.Unsatisfactory performance of a pile in rock is usually a displacement issue and is a function of rock mass stiffness rather than rock mass strength. In addition, poor pile performance is much more likely to result from poor construction practices than excessive displacement of the rock mass. Exceptions occur for footings that are undermined, or where unfavourable structure in the rock allows movement towards a free surface to occur. Standards, codes of practices, reference books and other sources of design information should focus foundation design in rock on displacement rather than strength performance.Ground investigations should measure rock mass stiffness and defect properties, as well as intact rock strength. This paper summarises the fundamental concepts relating to performance of piles in rock and provides a basis for displacement focused design of piles in rock. It also presents comments relating to how piles are modelled in widely used commercial finite element software for soil-structure interaction analysis, within the context of the back-analysis of a pile load test, and proposes recommendations for pile analysis and design.     

双排桩桩间土加固作用在长江一级阶地深基坑工程中的应用分析

简化双排桩桩间土加固体为实体杆单元,采用水平向的桩土作用弹簧与前后排支护桩相连接,考虑其抗剪及抗弯能力,在双排桩桩土相互作用计算模型的基础上,提出了计算前后排桩间土加固作用对支护结构内力及变形影响的方法。结合武汉市长江一级阶地基坑工程实例,将计算结果与实测值进行对比分析,以验证该计算方法的可行性与实用性,以期为同类型基坑支护设计提供有益参考。     

An approach for 2D modelling of laterally loaded piles

Despite a considerable progress in the analysis and design of monopiles, many methods are based on complex mathematical structures with doubtful or hard assumptions to verify. Therefore, there is still a need for simple and yet accurate methods for the analysis of monopiles under drained and undrained lateral cyclic loading conditions. In this work, a simple yet efficient two-dimensional modelling approach for the analysis of monopiles is proposed. To account for out-of-plane frictional forces, counter-forces derived from virtual frictional forces generated at the out-of-plane pile interface are applied along the pile length together with the scaled pile stiffness. The predictive capabilities of the proposed approach were validated by back-calculating two different experimental sets. The first consists of a small-scale field monopile test on a coarse-grained soil subjected to lateral cyclic loading under drained conditions. The second is a centrifuge test involving a fine-grained soil subjected to lateral cyclic loading under practically undrained conditions. Simulation results with the proposed approach suggest an accurate prediction of pile displacements and bending moments under both drained and undrained lateral cyclic conditions. The method is, however, unable to reproduce pore water pressures generated behind the pile in low permeability materials.