Numerical evaluation of the soil behavior during impact driving of pipe-piles

During the impact driving of pipe-piles, the soil is influenced in different ways including the void ratio, stress distribution, and plugging formation. Such effects may play an important role in structural design criteria such as the pile’s lateral support provided by the soil. Hence, this work is focused on investigating the change in the mechanical characteristics of the soil during impact driving using an advanced numerical analysis tool which is validated against an experiment. The investigation includes the pile penetration behavior, plugging formulation inside the pile, and the change of the lateral stress in the soil during the pile installation. The proposed numerical model is shown to provide similar results compared to experimental measurements. The void ratio of the soil is influenced due to pile driving up to a lateral and vertical distance of 2D and 1D, respectively, where D is the pile diameter. Compared to the initial void ratio, the soil inside the pile experienced loosening about 20% while the soil outside is densified about 30% during driving. Moreover, the induced lateral stress inside is more than the one outside the pile, indicating the formation of plugging. Compared to the initial lateral stress state, the pile installation increased the lateral stress up to four times inside and two times outside the pile. Based on the findings of this work, the effects of driving on soil mechanical properties are not minimal and may affect the pile performance including the lateral resistance of the pile. By using the numerical approaches such as one in this study, the evaluation of the various effects on the soil due to pile driving and gaining a better understanding of the such complex problems are possible

Numerical evaluation of the pipe-pile buckling during vibratory driving in sand

The buckling of steel pipe piles during vibratory driving is numerically studied using the Multi-Material Arbitrary Lagrangian-Eulerian (MMALE) method. This method handles the large soil deformations that occur during pile driving and other geotechnical installation processes. The Mohr-Coulomb and an elastic-perfectly plastic material model are used to model the soil and the pile mechanical behavior, respectively. The result of a small-scale pile driving experiment is used to validate the numerical model. The penetration trend agrees well with the experimental measurements. Thereafter, four case scenarios and their possible effects on pile buckling, namely the presence of heterogeneity in the soil (a rigid boulder inside the soil) and the existence of geometrical imperfection modes in the pile (ovality, out-of-straightness, flatness) are investigated. This study shows that a combination of local and global buckling initiates at the pile tip and the pile shaft, respectively. During the initiation of buckling, a decrease in the penetration rate of the pile is observed compared to the case where no or minimal buckling occurs. It is shown that a less portion of the driving energy is spent on the pile penetration and the rest is spent on other phenomena such as buckling, resulting in less pile penetration. The cross section of the pile tip after buckling takes a form of a “peanut”, yet with a different geometry for each case. In cases where the model was initially symmetric, an asymmetric shape in cross section of the pile tip was obtained at the final stage which can be attributed to complex soil-structure interaction. The results of the numerical approach provide promising results to be used as an evaluation tool to reach reliable predictions in pile installation practice

Segmental stabilizing exercises and low back pain: What is the evidence?

Study design: A systematic review of randomized controlled trials. Objectives: To evaluate the effectiveness of segmental stabilizing exercises for acute, subacute and chronic low back pain with regard to pain, recurrence of pain, disability and return to work. Methods: MEDLINE, EMBASE, CINAHL, Cochrane Controlled Trials Register, PEDro and article reference lists were searched from 1988 onward. Randomized controlled trials with segmental stabilizing exercises for adult low back pain patients were included. Four comparisons were foreseen: (1) effectiveness of segmental stabilizing exercises versus treatment by general practitioner (GP); (2) effectiveness of segmental stabilizing exercises versus other physiotherapy treatment; (3) effectiveness of segmental stabilizing exercises combined with other physiotherapy treatment versus treatment by GP and (4) effectiveness of segmental stabilizing exercises combined with other physiotherapy treatment versus other physiotherapy treatment. Results: Seven trials were included. For acute low back pain, segmental stabilizing exercises are equally effective in reducing short-term disability and pain and more effective in reducing long-term recurrence of low back pain than treatment by GP. For chronic low back pain, segmental stabilizing exercises are, in the short and long term, more effective than GP treatment and may be as effective as other physiotherapy treatments in reducing disability and pain. There is limited evidence that segmental stabilizing exercises additional to other physiotherapy treatment are equally effective for pain and more effective concerning disability than other physiotherapy treatments alone. There is no evidence concerning subacute low back pain. Conclusion: For low back pain, segmental stabilizing exercises are more effective than treatment by GP but they are not more effective than other physiotherapy interventions

Geotechnical and Environmental Consideration by Planning and Construction of the Transportation Infrastructure in the Centre of Berlin

Since the mid of the nineties in the City of Berlin there have been built underground installations, i.e. railway and street tunnels as well as foundations deep embedded in the groundwater, with some extraordinary measures. The surface area of all tunnel constructions of the VZBProject (inner city traffic tunnels in Berlin) amounts to approx. 240,000 square meters. The excavation pits for the tunnel structures have depths of more than 20 meters and widths of more than 100 meters. All this projects lead in the mid nineties to the characterization of the City of Berlin as Europe`s biggest construction site. A general overview of the transportation infrastructure project will be given here. A number of technical problems had to be resolved and new strategies devised at the planning stage because of the geotechnical and hydrogeological conditions in the central area of Berlin, the environmental requirements concerning groundwater conditions, and interaction with the surrounding green area and the nearby existing buildings. Several methods of tunnelling constructions in cohesionless soils with high ground water level were applied, such as caissons, shield driven tunnels and trough-type excavations (cut-and-cover tunnels). The geotechnical and hydrogeological conditions will be presented and the planning and realization of the tunnelling construction methods will be explained in the paper. Quality assurance was an important issue of the project and included an extensive monitoring system to ensure the quality of the constructions and to control the prior design and calculations. The impact of the project on the urban life and on the environment wouldn`t be minimized without a sophisticated project and ground water management. A very extensive measurement program in the frame of the quality assurance and geotechnical observation method was performed. It consisted of tension loading tests of single piles and groups of piles as well as measurements of anchor forces, wall deformations, uplift and leak water. Some data of monitoring are presented and discussed in this case history report

Butyrate Permeation across the Isolated Ovine Reticulum Epithelium

We hypothesized that, due to the high pH of this compartment, the reticulum epithelium displays particular features in the transport of short-chain fatty acids (SCFA). Ovine reticulum epithelium was incubated in Ussing chambers using a bicarbonate-free buffer solution containing butyrate (20 mmol L−1). p-hydroxymercuribenzoic acid (pHMB), 5-(N-Ethyl-N-isopropyl)amiloride (EIPA), or ouabain were added to the buffer solution as inhibitors of monocarboxylate transporters, sodium-proton-exchangers, or the Na+/K+-ATPase, respectively. The short-circuit current (Isc) and transepithelial conductance (Gt) were monitored continuously while the flux rates of 14C-labelled butyrate were measured in the mucosal-to-serosal (Jmsbut) or serosal-to-mucosal direction (Jsmbut). Under control conditions, the mean values of Isc and Gt amounted to 2.54 ± 0.46 µEq cm−2 h−1 and 6.02 ± 3.3 mS cm−2, respectively. Jmsbut was 2.1 ± 1.01 µmol cm−2 h−1 on average and about twice as high as Jsmbut. Incubation with ouabain reduced Jmsbut, while Jsmbut was not affected. The serosal addition of EIPA did not affect Jmsbut but reduced Jsmbut by about 10%. The addition of pHMB to the mucosal or serosal solution reduced Jmsbut but had no effect on Jsmbut. Mucosally applied pHMB provoked a transient increase in the Isc. The serosal pHMB sharply reduced Isc. Our results demonstrate that butyrate can be effectively transported across the reticulum epithelium. The mechanisms involved in this absorption differ from those known from the rumen epithelium

Digital transformation: from hierarchy to network-based collaboration? The case of the German "Online Access Act"

To unlock the full potential of ICT-related public sector innovation and digital transformation, governments must embrace collaborative working structures and leadership, is commonly argued. However, little is known about the dynamics of such collaborations in contexts of hierarchy, silo cultures, and procedural accountability. A widely voiced but empirically insufficiently substantiated claim is that bringing cross-cutting digital endeavours forward requires more lateral, network-based approaches to governance beyond traditional Weberian ideals. We test this claim by shedding light on three distinct challenges (complexity, risk, and power imbalance) encountered when implementing the specific collaborative case of the German Online Access Act (OAA) and by examining how they have been addressed in institutional design and leadership. Our analysis, which combines desk research and semi-structured expert interviews, reveals that flexible, horizontal approaches are on the rise. Taking a closer look, however, vertical coordination continues to serve as complementary means to problem-solving capability.Dass Regierungen kooperative Arbeitsstrukturen und Führungsformen annehmen müssten, ist eine gängige Forderung, um das Potenzial von IKT-bezogener Innovation und digitaler Transformation im öffentlichen Sektor auszuschöpfen. Bislang ist jedoch wenig über die Dynamik solcher Kooperationen unter Rahmenbedingungen bekannt, die durch Hierarchie, Silokulturen und prozedurale Verantwortlichkeit charakterisiert sind. Auch empirisch nicht ausreichend untermauert ist die weit verbreitete Behauptung, die Förderung bereichs-übergreifender, digitaler Bestrebungen erfordere laterale, netzwerkbasierte Governance-Ansätze, die über die traditionellen Weber'schen Ideale hinausgehen. Wir prüfen diese Annahme, indem wir drei spezifische Herausforderungen (Komplexität, Risikowahrnehmung und Machtasymmetrien), die bei der Umsetzung des deutschen Onlinezugangsgesetz (OZG) aufgetreten sind, näher beleuchten, und untersuchen, wie diesen mit Maßnahmen des institutionellen Designs und Leadership begegnet wurde. Unsere Analyse kombiniert Literaturrecherchen mit semi-strukturierten Experteninterviews und zeigt, dass flexible, horizontale Ansätze an Relevanz gewinnen. Gleichzeitig wird jedoch deutlich, dass vertikale Koordination weiterhin als komplementäres Mittel zur Problemlösung Anwendung findet

Management of large construction projects and risk minimization by web-based software technology

Risk and Reliability in Geotechnical Engineerin

Theory and Numerical Modeling of Geomechanical Multi-material Flow

Multi-material flow describes a situation where several distinct materials separated by sharp material interfaces undergo large deformations. The research presented in this paper addresses a particular class of multi-material flow situations encountered in geomechanics and geotechnical engineering which is characterized by a complex coupled behavior of saturated granular material as well as by a hierarchy of distinct spatial scales. Examples include geotechnical installation processes, liquefaction-induced soil failure, and debris flow. The most attractive numerical approaches to solve such problems use variants of arbitrary Lagrangian–Eulerian descriptions allowing interfaces and free surfaces to flow through the computational mesh. Mesh elements cut by interfaces (multi-material elements) necessarily arise which contain a heterogeneous mixture of two or more materials. The heterogeneous mixture is represented as an effective single-phase material using mixture theory. The paper outlines the specific three-scale mixture theory developed by the authors and the MMALE numerical method to model and simulate geomechanical multi-material flow. In contrast to traditional flow models which consider the motion of multiple single-phase materials or single multi-phase mixture, the present research succeeds in incorporating both the coupled behavior of saturated granular material and its interaction with other (pure) materials.DFG, 76838227, Numerische Modellierung der Herstellung von Rüttelinjektionspfähle