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Charakterystyka lessów lubelskich jako podłoża budowlanego

Nepelski Krzysztof

Przegląd Geologiczny

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2021

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Vol. 69, nr 12

835--849

EN

The loess subsoil constitutes over 50% of the Lublin area and determines the geotechnical conditions of the western side of the River Bystrzyca. The paper discusses the geological structure of this part of Lublin and presents an analysis of the results of field research carried out by the author. The research methodology and the method of deriving parameters for the loess subsoil are also proposed. The Lublin loesses were divided into three main facies groups: aeolian (typical loess), aeolian-diluvial and aeolian-alluvial. The basis for the division and parametric characteristics of individual facies were mainly in-situ tests: CPT/CPTU static soundings, DMT/SDMT flat dilatometer tests and PMT Menard pressuremeter tests. The collected data allowed characterizing each of the facies groups and developing a synthetic geological cross-section representing the geological structure of the western part of Lublin. The number of analysed tests allowed stating that the data from CPT/CPTU static soundings are representative for Lublin. Data from DMT/SDMT tests can be considered representative, but further research is needed to refine them and, for example, to separate them by facies. Data from pressuremeter tests should be treated as preliminary. The analyses show that the most common facies in Lublin is silty aeolian one called typical loess, which, according to the author, constitutes approximately 75-80%, and their parameters are of key importance for the design of buildings. The remaining facies groups are about 8-15% for aeolian-diluvial loess and 8-10% for aeolian alluvial loess. Typical loesses are macroscopically homogeneous, but their varying stiffness is reflected in in-situ tests. The basic research method for loess subsoil should be CPT/CPTU static soundings, while the most representative parameter for geotechnical layers is the cone resistance qc. Details of the geological structure and parameters should be performed with DMT, SDMT and PMT tests, as well as laboratory tests, the necessary scope of which can be determined after the development of the subsoil model from the results of CPT tests.

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Podstawowe zasady i nowe możliwości wykorzystywania wyników badań presjometrycznych

Tarnawski M.

Przegląd Geologiczny

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2017

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Vol. 65, nr 10/2

725--736

EN

This article is an attempt to briefly summarize the achievements of the pressuremeter research methodology and its development paths in over sixty years of its existence. The current rules for the tests execution and interpretation of their results as well as their application in the foundation design and in geological-engineering evaluation of the sites are discussed and subjected to critical analysis. Attention has been drawn to the unique ability to identify and estimate errors that may occur during testing, and the last chapter outlines the prospects for the development of this research technique. The author has also presented his accomplishments, such as the introduction of the concept of maximum and minimum settlement, a new way for determining the creep pressure, and a simplified way of defining the so-called standard settlement. In conclusion, the author has drawn attention to the numerous advantages of the pressuremeter method. These include, in particular, a direct assessment of the two most important characteristics of the soil: strength (bearing capacity) and compressibility, reduction of scale effect and the ability to test the soil at any depth.

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The uses of the pressuremeter test for the design of North Transversal Tunnel in Grenoble

Chapeau C., Dembicki E., Kurek N., Marbach G., Monnet J.

Archives of Civil Engineering

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2006

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Vol. 52, nr 1

87-104

EN

The tunnel's construction in urban area is a particularly sensitive problem due to the careful security requirements, which must be applied to prevent tunnel from failure and from large displacements and to avoid damage to existing buildings. The tunnel of the North Transversal Road of Grenoble begins from Sablon district, crosses under river Isere, passes under Ile Verte district, crosses a second time under river Isere and joins the motorway A48 at Porte de France, and A480 at Pont du Vercors. In this area alluvial soils are observed with silty sands and clays and rock with the Chartreuse limestone. Along the tunnel construction the different layers of the soil were studied. Deformation and failure parameters are measured by cyclic and standard pressuremeter tests with push in slotted tube probe because sampling of silty sands under the water table is very difficult. The tests are used to determine the angle of friction of the soil, the cohesion of the clay and the Young's modulus. The results of the pressuremeter tests are used for the statistical calculations with the EXTREME program, which determine the mean value X, the standard deviation, the characteristic value Xk, and the theoretical distribution of each parameter. The characteristic values of the angle of friction for each families of the soil are computed. Characteristic values are calculated so that there is a probability (equal to 5%) that a new experimental value would be smaller than angle of friction. The Normal, Log Normal, Exponential, Weybull, Gamma, Chi2, Student, Pareto distributions are tested and are checked by the Anderson-Darling ( A-D ) test. The data variability of the geomechanical parameters is taken into account for the design of the project and for the safety of the tunnel drilling.

PL

Wykonanie konstrukcji tunelu w strefie mocno zurbanizowanej jest szczególnie trudnym zagadnieniem. Dlatego też należy spełnić liczne wymagania aby zapobiec zniszczeniu tunelu jak również istniejących budynków. Tunel będzie przebiegał przez okręg Sablon przecinając rzekę Isere, okręg Ile Verte oraz po raz drugi rzekę Isere a następnie zostanie przyłączony do autostrady A48. W tym obszarze obserwuje się grunty aluwialne nanoszone przez rzekę z przewarstwieniami mułów, glin oraz wapieni Chartreuse. W strefie gdzie ma przebiegać tunel wykonano badania parametrów gruntu za pomocą presjometru używając standardowej procedury obciążenie-odciążenie. To pozwoliło wyznaczyć kąt tarcia wewnętrznego, spójność oraz moduł Young'a. Wyniki otrzymane z badań presjometrycznych wykorzystano do obliczeń statystycznych za pomocą programu Extreme, który wyznacza wartość średnią X, odchylenie standardowe, wartość charakterystyczną Xk i rozkład teoretyczny każdego z parametrów. Obliczono wartość charakterystyczną kąta tarcia wewnętrznego dla każdej rodziny gruntów z prawdopodobieństwem (równym 5%), że nowa wartość doświadczalna będzie mniejsza niż kąt tarcia wewnętrznego. Badano rozkłady: normalny, log normalny, wykładniczy, Weybull, Gamma, Chi2, Student, Pareto, które sprawdzono testem Anderson-Darling. Zmienność parametrów geotechnicznych uzyskanych z obliczeń statystycznych przyjęto do projektu tunelu.