Comparative laboratory and in-situ measurements were used to establish the relationships between the static moduli of deformation calculated under the ED methodology and the DB methodology. The measurements proved that the moduli of deformation determined in accordance with the two methodologies cannot be substituted for each other.

Horníček, L.

Krejčiříková, H.

Lidmila, M.

Tyc, P.

Acta Polytechnica

English

CTU Open Journal Systems (Czech Technical University, Prague / České vysoké učení technické v Praze)

1 IntroductionWhile building the fixed track section from Třebovice toRudoltice in 2005, the substructure was designed in accor-dance with the regulations in force for DB (German FederalRailways). The requirement for the bearing capacity of thesubstructure subgrade was 120 MPa, i.e. a value greatlyexceeding the requirements of SŽDC (Czech Railway Infra-structure Administration) for corridor tracks. Ministry ofTransport of the Czech Republic research projectNo.1F52H/052/130 [1] was therefore charged with inves-tigating the correlations between the static modulus ofdeformation determined under the regulations of ČD (CzechRailways) and DB. Comparative measurements were carriedout in laboratory conditions in an experimental box (ongravel and granulated gravel) and in in-situ conditions (onsand and soil).2 Measurement of moduli ofdeformation at SŽDC (ČD)The requirements for the measuring apparatus, a detailedtest procedure and its assessment are regulated in instructionČD S4 Substructure [2] and in standard ČSN 72 1006 Check-ing the compaction of soils and fills [3]. At the begining of themeasurements, to ensure tight fitting of individual parts ofthe load device, short-term loading not exceeding 10 s is acti-vated, which must not generate a pressure on the loaded layergreater than 20 % of the maximum plate load. The initialreading is taken after the load is removed and the path indica-tors are stabilized. The plate is then gradually loaded in foursteps of equal magnitude. For each loading step, the deforma-tion of the subsoil under the plate is recorded. If the change indeformation during 1 minute is less than 0.02 mm, it is con-sidered as stabilized and the next loading step follows. Theprocedure continues in the same way until the maximum loadrequired for the loaded layer is reached. Later the load plateis relieved in the same steps down to zero load, and the cycle isrepeated for the second time.During the test, the plate load values are read on the loadgauge and the plate insertion is read on the path indicators.The mean load plate insertion values in each loading andload removal step are plotted in a chart expressing the rela-tionship between the specific pressure acting on the load plateand the load plate insertion. The value of the total mean plateinsertion from the loading branch of the second cycle is en-tered in the chart with a simultaneous calculation of themodulus of deformation using general formula:Ep ry1 5. ,where E is static modulus of deformation [MPa],p specific pressure acting on the load plate [MPa],r load plate radius, i.e. 0.15 [m],y total mean load plate insertion determined inthe loading branch of the second cycle [m].The specific pressure on the load plate is selected as fol-lows: on earth subgrade p  0.2 MPa with a loading step of0.05 MPa, for less bearing soils p  0.1 MPa with a loading stepof 0.025 MPa; on a structural layer of the substructure bodyp  0.2 MPa with a loading step of 0.05 MPa; and on the railbed at sleeper loading area  0.4 MPa with a loading stepof 0.10 MPa (Note: since 1. 1. 2003 the bearing capacity atthis level has no longer been assessed). The measurement ofthe modulus of deformation in the experimental box on thesurface of a granulated gravel layer is shown in Fig. 1.3 Measurement of moduli ofdeformation at DBThe requirements for the measuring apparatus, the de-tailed test procedure and its assessment are regulated inGerman standard DIN 18 134 Plattendruckversuch [3]. Atthe begining of the measurement, a preload of ca 0.01 MPa isactivated to be removed in about 30 seconds, and the readingon the path indicators is set at 0.00 mm. The test proce-dure consists of two loading branches and one load removalbranch. A plate with a diameter of 300 mm is loaded untilthe plate insertion reaches a value of ca 5 mm or a specificpressure of 0.50 MPa. The load is added step by step in at least6 roughly identical steps. In each loading step, the path indi-52 ©  Czech Technical University Publishing House http://ctn.cvut.cz/ap/Acta Polytechnica Vol. 46  No. 3/2006 Czech Technical University in PragueProblems in Different Measuring andAssessment the Modulus of DeformationUsing the Czech and GermanMethodologiesM. Lidmila, L. Horníček, H. Krejčiříková, P. TycComparative laboratory and in-situ measurements were used to establish the relationships between the static moduli of deformationcalculated under the ČD methodology and the DB methodology. The measurements proved that the moduli of deformation determined inaccordance with the two methodologies cannot be substituted for each other.Keywords: Modul of deformation, conventional Trans-European System, the substructure, Classification of Soils, the earth subgrade, thefixed track section, the corridor track, rubber plates, granulated gravel, the correlation coefficient.cators are read at 120 second intervals, and in the case ofload-bearing layers this time may be reduced to 60 seconds.When measuring with 3 path indicators, the reading on thefirst indicator is taken 10 seconds before the waiting time ex-piry. The path indicators are always read in the same orderand at identical time intervals. Load removal is carried out in3 steps – 50 %, 25 % and 0 % of the maximum plate load. Thesecond loading branch terminates in the last but one step ofthe first loading branch.The modulus of deformation (Verformungsmodul) is cal-culated from both the first and the second loading branch. Itis determined from the loading chart, from the inclination ofthe secant line between two points given by the value of the0.3- and 0.7-multiple of the maximum load, using the generalformula:E rsv  15.,where Ev is static modulus of deformation [MPa],r load plate radius, i.e. 0.15 [m],y total mean load plate insertion determined inthe loading branch of the second cycle [m], difference in the value of the 0.3- and 0.7-multi-ple of the maximum load [MPa],s difference in the load plate insertion betweenthe value of the 0.3- and 0.7-multiple of themaximum load [MPa].4 Measurement of moduli ofdeformation on rail bed modelsIn order to establish the correlation between the moduli ofdeformation of rail bed structures determined in accordancewith the Czech and German methodologies in laboratoryconditions, the experimental box of the Department of Rail-way Structures of the Faculty of Civil Engineering, CTU inPrague was used. The experimental box consists of weldedsteel sections and removable walls of wooden planks. Thewalls of the box walls were lined with a thin galvanized plate tominimize the friction of the model at contacts with the wallsof the box. The basic dimensions of the inside space of theexperimental box are: length: 2095 mm, width: 990 mm,height: 800 mm. The experimental box also includes a mov-able frame, which enables load press to be propped whilemeasuring the moduli of deformation on models in theexperimental box.The experimental box was used for experimental moni-toring of 4 rail bed models in a 1:1 scale composed of rubberplates simulating earth subgrade with different bearing ca-pacities (10.9 MPa, 25 MPa), structural layers of granulatedgravel of 0/32 mm grading with different thicknesses (15 cm,30 cm) and a rail bed of gravel of 32/63 mm grading witha constant thickness of 35 cm. The gravel and granulatedgravel were exposed to a grain composition test, whichproved that the grain size composition of these materials issuitable for use in rail beds or in structural layers of thesubstructure body.The moduli of deformation were determined at threeheight levels: on a simulated earth subgrade, on a layer ofgranulated gravel and on a layer of gravel. The individualmodels were labelled with codes containing information onthe thickness of the structural layer in cm, abbreviations ofthe material used for the structural layer and the approxi-mate bearing capacity of the simulated earth subgrade in MPa(e.g. 15SD E10). Characteristic data for each model is pre-sented in Tab. 1. The model of the 5SD E10 structure in theexperimental box is shown in Fig. 2.The structural layer was composed of either one or twolayers, 150 mm in thickness, and the rail bed consisted of twolayers, 175 mm in thickness. The individual layers were com-pacted with a special manual vibrating compacting devicewith a compacting area of 174×174 mm, and each layer wasuniformly compacted for 30 minutes along the whole surfaceof the experimental box.©  Czech Technical University Publishing House http://ctn.cvut.cz/ap/ 53Czech Technical University in Prague Acta Polytechnica Vol. 46  No. 3/2006Fig. 1: Measuring the static modulus of deformation on a granu-lated gravel layer in the experimental boxModellabellingEarth subgradebearing capacityin MPaStructural layerthickness inmmRail bedthicknessin mm15SD E10 10.9 150 35030SD E10 10.9 300 35015SD E25 25.0 150 35030SD E25 25.0 300 350Table 1: Labelling of rail bed models and their characteristics5 Measurements of moduli ofdeformation on a layer of gravelAfter each model, had been constructed, the three plateload tests on a layer of gravel were performed following theČD methodology and then, in identical positions, three plateload tests were performed following the DB methodology.This measurement method was selected due to the confinedplan of the model. Inaccuracy in determining of the modulusof deformation under the DB methodology, however, willbe insignificant. The composition of the 15SD E10 modelwith schematic positions of the circular load plate is shown inFig. 2. The determined values of the moduli of deformationare given in Table 2.6 Measurements of moduli ofdeformation on a layer ofgranulated gravelOnce the plate load tests on a layer of gravel were com-pleted, the gravel was removed from each model, and threeplate load tests were performed on a layer of granulatedgravel under the ČD methodology and subsequently, in iden-tical positions, three plate load tests were performed underthe DB methodology. The determined values of the moduliof deformation are given in Table 3.7 Measurements of moduli ofdeformation on sandThe location selected for in-situ measurements of themoduli of deformation was the Klíčany sand pit, where sandwith fine soil admixtures is quarried. The measurements werecarried out at two points (field No. 1 and field No. 2) withthe natural placement of sand layers showing no significantdisintegration due to the extraction machinery. The counter-weight used during the measurement of the static moduli ofdeformation was a loaded lorry. In all, six plate load tests wereperformed using the ČD methodology and six plate load testsusing the DB methodology. Once the plate load tests werecompleted, holes were dug at the measurement points to adepth of 1.0 m. These dug holes served for taking disinte-grated samples for geotechnical laboratory analyses whichproved that the tested layer of sand can be classified underČSN 72 1002 [5] as sand with fine soil admixtures (S3 S-F)with a mean natural moisture content of 7.8 % in field No. 1and 5.5 % in field No. 2. The determined values of the moduliof deformation are given in Table 4. Fig. 3 shows the modulusof deformation being measured on a layer of sand in theKlíčany sand pit.54 ©  Czech Technical University Publishing House http://ctn.cvut.cz/ap/Acta Polytechnica Vol. 46  No. 3/2006 Czech Technical University in Praguea) b)Fig. 2: Rail bed structure model 15SD E10 in the experimental box: a) longitudinal section, b) cross sectionModel labellingMean modulus of deformation in MPaČD methodology DB methodology15SD E10 63.8 71.330SD E10 79.4 98.315SD E25 90.0 104.530SD E25 103.9 117.7Table 2: Moduli of deformation on a gravel surface for eachmethodologyModel labellingMean modulus of deformation in MPaČD methodology DB methodology15SD E10 26.1 23.030SD E10 53.3 48.915SD E25 50.1 44.130SD E25 82.9 86.4Table 3: Moduli of deformation on a granulated gravel surfacefor each methodology8 Measurements of moduli ofdeformation on soilThe location selected for in-situ measurements of themoduli of deformation was the construction site of an em-bankment at Svojšovice as part of corridor IV within theŘíčany – Stránčice section. The measurement was carried outon a compacted layer of highly non-homogeneous materialcompacted at two points (field No. 1 and field No. 2). Thecounterweight used was a flat vibratory roller or a loadedlorry. In all, six plate load tests were performed using the ČDmethodology and six plate load tests using the DB metho-dology. Once the plate load tests were completed, holes weredug at the measurement points to a depth of 0.5 m. Thesedug holes served for taking disintegrated samples for geo-technical laboratory analyses which proved that the layer ofsoil can be classified under ČSN 72 1002 [5] as dirty gravel(G5 GC) to gravel with fine soil admixtures (G3 GF) with amean natural moisture content of 12.7 % in field No. 1, whilethe soil layer in field No. 2 is composed of gravely clay(F2 CG) to gravely loam (F1 MG) with a mean moisturecontent of 15.8 %. The values of the moduli of deformationare shown in Table 5.9 Correlation coefficientsIn order to express the relationship of the moduli ofdeformation determined under the ČD methodology andunder the DB methodology, the correlation coefficients werecalculated from the formula:kEEDBČD,where k is correlation coefficient [-],EDB modulus of deformation determined under theGerman methodology from the second loadingbranch [MPa],EČD modulus of deformation determined under theCzech methodology [MPa].The correlation coefficients of the moduli of deformationon a layer of gravel are shown in Table 6, and on a layer ofgranulated gravel in Table 7.©  Czech Technical University Publishing House http://ctn.cvut.cz/ap/ 55Czech Technical University in Prague Acta Polytechnica Vol. 46  No. 3/2006Fig. 3: Static modulus of deformation being measured on a layer of sand in the Klíčany sand pitFieldlabellingMean naturalmoisturecontent in %Mean modulus of deformationin MPaČDmethodologyDBmethodologyField No. 1 8.7 82.2 136.8Field No. 2 5.5 38.7 67.4Table 4: Moduli of deformation on sand for each methodologyFieldlabellingMean naturalmoisturecontent in %Mean modulus of deformationin MPaČDmethodologyDBmethodologyField No. 1 12.7 92.1 66.3Field No. 2 15.8 56.0 45.6Table 5: Moduli of deformation on soil for each methodologyThe correlation coefficients of the moduli of deformationon sand are given in Table 8 and on soil in Table 9.10 ConclusionThe correlation coefficients determined in our experi-ment lead to the following conclusions:1. The ČD and DB methodologies for measuring the staticmoduli of deformation apply the same testing apparatus(a circular load plate with a diameter of 30 cm), butthe prescribed plate load loading is different and so isthe calculation procedure for the static modulus ofdeformation.2. Comparative measurements of static moduli of defor-mation show that the correlation dependency emergingfrom the determined moduli of deformation k  EDB/EČDshows considerable differences both for different materi-als and for multi-layer systems of various materials. Forexample, the measurements revealed fluctuations in cor-relation coefficient “k” in the range of 0.76 to 1.70. Indesigning the track body, the values of the static moduliof deformation as determined under the ČD metho-dology and the DB methodology cannot be substitutedfor each other.3. In designing the rail bed on SŽDC tracks, the require-ments for the load-bearing capacity of individual layersmust be respected as regulated in instruction ČD S4 Sub-structure. The requirements given by instruction ČD S4Substructure cannot be substituted for the requirementsgiven by instruction DS 836 Vorschrift für Erdbauwerkeapplied by DB.4. In the case of a potential change in the ČD methodologyfor measuring of the static modulus of deformation (e.g.by taking over a uniform European standard), instructionČD S4 Substructure, ČSN 72 1006 Checking the compac-tion of soils and fills and other related regulations wouldhave to undergo considerable modifications.11 AcknowledgmentThis paper was written within the research projectNo. 1F52H/052/130 funded by Ministry of Transport of theCzech Republic.References[1] Krejčiříková, H., Tyc, P., Lidmila, M., Horníček, L.,Voříšek, P., et al.: Methodology of Transitional Parametersfor the Construction of Substructure and Tracks of the Conven-tional Trans-European System. Research reports of project1F52H/052/130, Faculty of Civil Engineering, CTU inPrague, Department of Railway Structures, 2005 and2006.[2] Instruction ČD S4 Substructure, 1997 (in force since1. 7. 1998).[3] ČSN 72 1006 Checking the Compaction of Soils andFills. Český normalizační institut, 1998.[4] DIN 18 134 Plattendruckversuch. Deutsches Institut fürNormung e. V., 1993.[5] ČSN 72 1002 Classification of Soils for TransportationStructures. Český normalizační institut, 1993.Ing. Martin Lidmila, Ph.D.e-mail: lidmila@fsv.cvut.czIng. Leoš Horníček, Ph.D.e-mail: leos.hornicek@fsv.cvut.czDoc. Ing. Hana Krejčiříková, CSc.phone: +420 224 354 756e-mail: krejcirikova@fsv.cvut.czProf. Ing. Petr Tyc, DrSc.e-mail: petr.tyc@fsv.cvut.czDepartment of Railway StructuresCzech Technical University in PragueFaculty of Civil EngineeringThákurova 7166 29 Praha 6, Czech Republic56 ©  Czech Technical University Publishing House http://ctn.cvut.cz/ap/Acta Polytechnica Vol. 46  No. 3/2006 Czech Technical University in PragueModellabellingMean correlationcoefficient “k”Total mean correlationcoefficient “k”15SD E10 1.121.1730SD E10 1.2415SD E25 1.1630SD E25 1.13Table 6: Correlation coefficients on a layer of gravelModellabellingMean correlationcoefficient “k”Total mean correlationcoefficient “k”15SD E10 0.880.9430SD E10 0.9215SD E25 0.8830SD E25 1.04Table 7: Correlation coefficients on a layer of granulated gravelModellabellingNaturalmoisturecontent in %Meancorrelationcoefficient “k”Total meancorrelationcoefficient “k”Field No. 1 12.7 0.720.76Field No. 2 15.8 0.81Table 9: Correlation coefficients on soilModellabellingNaturalmoisturecontent in %Meancorrelationcoefficient “k”Total meancorrelationcoefficient “k”Field No. 1 8.7 1.661.70Field No. 2 5.5 1.74Table 8: Correlation coefficients on sand

Problems in Different Measuring and Assessment the Modulus of Deformation Using the Czech and German Methodologies

Abstract

Similar works

Full text

Available Versions

CTU Open Journal Systems (Czech Technical University, Prague / České vysoké učení technické v Praze)

Directory of Open Access Journals