Jozef Vlček

Contribution to Estimating Bearing Capacity of Pile in Clayey Soils

Abstract The estimation of real geotechnical parameters is key factor for safe and economic design of geotechnical structures. One of these are pile foundations, which require proper design and evaluation due to accessing more deep foundation soil and because remediation work of not bearable piles or broken piles is a crucial operation. For this reason, geotechnical field testing like cone penetration test (CPT), standard penetration (SPT) or dynamic penetration test (DP) are realized in order to receive continuous information about soil strata. Comparing with rotary core drilling type of survey with sampling, these methods are more progressive. From engineering geologist point of view, it is more important to know geological characterization of locality but geotechnical engineers have more interest above the real geotechnical parameters of foundation soils. The role of engineering geologist cannot be underestimated because important geological processes in origin or during history can explain behaviour of a geological environment. In effort to streamline the survey, investigation by penetration tests is done as it is able to provide enough information for designers. This paper deals with actual trends in pile foundation design; because there are no new standards and usable standards are very old. Estimation of the bearing capacity of a single pile can be demonstrated on the example of determination of the cone factor Nk from CPT testing. Then results were compared with other common methods.

CPT Profiling and Laboratory Data Correlations for Deriving of Selected Geotechnical Parameter

Abstract Currently, can be seen a new trend in engineering geological survey, where laboratory analysis are replaced by in situ testing methods, which are more efficient and cost effective, and time saving too. A regular engineering geological survey cannot be provided by simple core drillings, macroscopic description (sometimes very subjective), and then geotechnical parameters are established based on indicative standardized values or archive values from previous geotechnical standards. The engineering geological survey is trustworthy if is composed of laboratory and in-situ testing supplemented by indirect methods of testing, [1]. The prevalence of rotary core drilling for obtaining laboratory soil samples from various depths (every 1 to 3 m), cannot be a more enhanced as continues evaluation of strata and properties e.g. by CPT Piezocone (every 1 cm). Core drillings survey generally uses small amounts of soil samples, but this is resulting to a lower representation of the subsoil and underestimation of parameters. Higher amounts of soil samples make laboratory testing time-consuming and results from this testing can be influenced by the storage and processing of the soil samples. Preference for geotechnical surveys with in situ testing is therefore a more suitable option. In situ testing using static and dynamic penetration tests can be used as a supplement or as a replacement for the (traditional) methods of surveying.

Experimental Investigation of Properties of Foam Concrete for Industrial Floors in Testing Field

Foam concrete (FC), as a mixture of cement, water, additives and technical foam, is well known for more than 30 years. It is building material with good mechanical properties, low thermal conductivity, simple and even high technological treatment. Foam concrete contains closed void pores, what allows achieving low bulk density and spare of raw materials. Thanks to its properties, it is usable as a replacement of conventional subbase layers of the industrial floors, the transport areas or as a part of the foundation structures of the buildings. Paper presents the preparation of the testing field (physical model) which was created for experimental investigation of the foam concrete subbase layer of the industrial floor in a real scale.

Experimental Investigation of the Vehicle–Ground Interaction – Experiment Preparation and Preliminary Results

Abstract Interaction of the moving vehicle and the ground represents the actual engineering, environmental and economic problem. Due to the complexity of the problem, a combination of the experimental measurement and the computational simulation to understand the interaction mechanism is the most beneficial approach. Results of the in-situ observation serve as an input for the numerical analysis and also as a background for the calibration of the model. Presented paper brings the summary of the experiment preparation and preliminary results which are necessary for further analyses and numerical models. Computational simulations will be helpful for understanding the vehicle-ground interaction when inputs will be verified by the experimental way at known boundary conditions.

Computational Simulation of Dynamic Response of Vehicle Tatra T815 and the Ground

The effect of a moving load represents the actual problem which is analysed in engineering practice. The response of the vehicle and its dynamic effect on the pavement can be analysed by experimental or computational ways. The aim of this paper was to perform computer simulations of a vehicle-ground interaction. For this purpose, a half-part model of heavy lorry Tatra 815 and ground was modelled in computational programmes ADINA and PLAXIS based on FEM methods, utilizing analytical approaches. Two procedures were then selected for further calculations. The first one is based on the simplification of the stiffer pavement layers to the beam element supported by the springs simulating the subgrade layers using Winkler-Pasternak theory of elastic half-space. Modulus of subgrade reaction was determined in the standard programme trough the simulation of a plate load test. Second approach considers a multi-layered ground system with layers of different thicknesses and material properties. For comparison of outputs of both approaches, the same input values were used for every calculation procedure. Crucial parameter for the simulations was the velocity of the passing vehicle with regard to the ground response to the impulse of the pass. Lower velocities result in almost static response of the pavement, but higher velocities induce response that can be better described by the dynamic theory. For small deformations, an elastic material model seems to be sufficient to define the ground response to the moving load, but for larger deformations advanced material models for the ground environment would be more reliable.

Analytical and Numerical Evaluation of Limit States of MSE Wall Structure

Reinforced soil structures (RSS) or mechanically stabilized earth structures (MSE) are widely used in transport construction now. These structures take advantage of reinforcement, which is defined as soil-inclusion stress transfer occurring continuously along the inclusion or reinforced element. Inclusion (reinforced element) is a generic term that encompasses all man-made elements incorporated in the soil to improve its behaviour, e.g. steel strips, geotextile, steel or polymeric grids – geogrids (GGR), nails and steel tendons between anchorage elements. Mechanically Stabilized Earth Wall (MSE wall or MSEW) is a generic term that includes reinforced soil (a term used when multiple layers of inclusions act as reinforcement in soils placed as fill), [1]. Reinforced soil structures since its introduction are designed and evaluated by the analytical methods of calculation, which in itself must include a certain amount of simplification and generalization. These methods are particularly effective for the geometry design, ultimate limit state evaluation, and the determination of the maximum tensile strength of the reinforcing elements and the necessary anchoring length to embankment fill. In contrast, numerical modelling allows a better view of the behaviour of structures in the phase of construction and operation as analytical methods, especially when assessing the serviceability limit state structures the level of maximum deflection. In addition to performing auxiliary tasks in assessing the serviceability limit state design, numerical modelling is an appropriate tool for complex design and assessment of reinforced retaining structures by geosynthetics.

Analysis of the Tyre Loads of the Truck Tatra 815 in Interaction with the Ground

Abstract Interaction between moving vehicle and ground represents the actual problem. Traffic seismicity affects the environment and causes worsening of its parameters. Several approaches have been developed to solve the phenomena of the vehicle-ground interaction. This problem needs to be analysed as a complex system when particular elements interact together. The interaction results in unique magnitudes of the contact forces. This paper presents the results of the analysis of vehicle-ground interaction. Calculations have been made in software ADINA using Finite Element Method. Dynamic characteristics of the vehicle have been determined according to the lorry Tatra 815. Contact forces of the tyres have been applied as point and distributed load respectively.

The Role of Geotechnical Monitoring at Design of Foundation Structures and their Verification – Part 1

Abstract For a long time, design of the square foundations has not posed a problem in engineering practice. Foundations are designed on the basis of determining the bearing capacity of the subsoil, where irregularities in its determination oftentimes affect the efficiency (economy), while possible failures of bearing resistance of foundation soil are rare. More important factor is the resulting deformation of second limit state under consideration - settlement, relative settlement, tilting and excessive deformation. The current pressure on the cost reduction of design preparation and obtaining important data from geotechnical survey often results in many cases into adverse effects of settlement and differential settlement of foundations of the buildings. The question lies in a variety of analytical methods for assessing the service ability of limit states used in European countries as well as the underestimation of the proposal risks. Authors of the article want to document the fact that the most important influence on adequate and safe design is the most accurate determination of geotechnical parameters and the appropriate selection of the calculation method. For the purposes of explanation, Monte Carlo simulation technique was used to test a variety of geotechnical parameters, which will be presented in second part of article. If all construction processes are carried out successfully, rarely are the buildings evaluated once again. However, when the opportunity to participate in the stage of engineering survey and collection of geotechnical parameters as well as the control of the construction process by tools of geotechnical monitoring presents itself, it is valuable to perform the analysis of the entire process for pointing out hidden risks.

ANALYSIS OF LIMITS STATES OF HIGH RETAINING WALLS REINFORCED WITH GEOSYNTHETICS

The main questions at design of the reinforced structures are: necessary tensile strength of reinforced elements depending on the face part type, inclination and chosen backfill material. The limit states are verified by analytical design methods. The evaluation of deformations of the reinforced retaining walls is a problem, especially at high walls. Numerical modelling has advantages in a detail simulation of construction processes, time factor and load intensity. Correct description of face element behaviour, especially the soft layout of wrap-around face or gabions, becomes crucial because of its high influence on the overall visible and measurable deformations on the face. In this case, basket and fill of gabions were modelled separately to achieve more realistic results. Realization of in-situ and laboratory tests on reinforced elements or application of large scale physical modelling can offer additional data to restrict the indefiniteness in modelling of key parts of the structure. Afterwards, it will be possible to evaluate the potential unsuitability of flexible face elements for high retaining walls as shows results of the numerical modelling.

Application of static penetration test for the determination ofgeotechnical parameters

The actual trends in geotechnical engineering, concerning assessment of geotechnical problems by numerical analysis by Plaxis, Flac, ZSoil, Abaqus, Crisp or Midas require adequate input settings, values, parameters. In addition to sophisticated laboratory procedures, the main reason to support the use of field testing is continuous characterization of the testing profile, immediate evaluation of the characteristics and type of soil and determination of geotechnical parameters needed for constitutive models of soils. Conventional surveying methods like core boring with sample extraction for laboratory tests can offer only limited point information about rock environment. In geological environments with clayey and silty soils the most common in-situ testing methods are static penetration test CPTm, CPTu with piezocone, and seismic cone SCPT. Estimation of soil properties based on results of the penetration tests is reliable only if the probe is made with provided boreholes, supplemented by laboratory tests. Sample data from CPT examination of foundation conditions along the route R1 Nitra, west - Beladice - Tekovske Nemce are presented to show the calculation of parameters for advanced constitutive models of soils.