AP06_3.vp 1 Introduction While building the fixed track section from Třebovice to Rudoltice in 2005, the substructure was designed in accor- dance with the regulations in force for DB (German Federal Railways). The requirement for the bearing capacity of the substructure subgrade was 120 MPa, i.e. a value greatly exceeding the requirements of SŽDC (Czech Railway Infra- structure Administration) for corridor tracks. Ministry of Transport of the Czech Republic research project No.1F52H/052/130 [1] was therefore charged with inves- tigating the correlations between the static modulus of deformation determined under the regulations of ČD (Czech Railways) and DB. Comparative measurements were carried out in laboratory conditions in an experimental box (on gravel and granulated gravel) and in in-situ conditions (on sand and soil). 2 Measurement of moduli of deformation at SŽDC (ČD) The requirements for the measuring apparatus, a detailed test procedure and its assessment are regulated in instruction ČD S4 Substructure [2] and in standard ČSN 72 1006 Check- ing the compaction of soils and fills [3]. At the begining of the measurements, to ensure tight fitting of individual parts of the load device, short-term loading not exceeding 10 s is acti- vated, which must not generate a pressure on the loaded layer greater than 20 % of the maximum plate load. The initial reading is taken after the load is removed and the path indica- tors are stabilized. The plate is then gradually loaded in four steps of equal magnitude. For each loading step, the deforma- tion of the subsoil under the plate is recorded. If the change in deformation during 1 minute is less than 0.02 mm, it is con- sidered as stabilized and the next loading step follows. The procedure continues in the same way until the maximum load required for the loaded layer is reached. Later the load plate is relieved in the same steps down to zero load, and the cycle is repeated for the second time. During the test, the plate load values are read on the load gauge and the plate insertion is read on the path indicators. The mean load plate insertion values in each loading and load removal step are plotted in a chart expressing the rela- tionship between the specific pressure acting on the load plate and the load plate insertion. The value of the total mean plate insertion from the loading branch of the second cycle is en- tered in the chart with a simultaneous calculation of the modulus of deformation using general formula: E p r y � � 1 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 in the 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 of 0.05 MPa, for less bearing soils p � 0.1 MPa with a loading step of 0.025 MPa; on a structural layer of the substructure body p � 0.2 MPa with a loading step of 0.05 MPa; and on the rail bed at sleeper loading area � 0.4 MPa with a loading step of 0.10 MPa (Note: since 1. 1. 2003 the bearing capacity at this level has no longer been assessed). The measurement of the modulus of deformation in the experimental box on the surface of a granulated gravel layer is shown in Fig. 1. 3 Measurement of moduli of deformation at DB The requirements for the measuring apparatus, the de- tailed test procedure and its assessment are regulated in German standard DIN 18 134 Plattendruckversuch [3]. At the begining of the measurement, a preload of ca 0.01 MPa is activated to be removed in about 30 seconds, and the reading on the path indicators is set at 0.00 mm. The test proce- dure consists of two loading branches and one load removal branch. A plate with a diameter of 300 mm is loaded until the plate insertion reaches a value of ca 5 mm or a specific pressure of 0.50 MPa. The load is added step by step in at least 6 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 Prague Problems in Different Measuring and Assessment the Modulus of Deformation Using the Czech and German Methodologies M. Lidmila, L. Horníček, H. Krejčiříková, P. Tyc Comparative laboratory and in-situ measurements were used to establish the relationships between the static moduli of deformation calculated under the ČD 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. Keywords: Modul of deformation, conventional Trans-European System, the substructure, Classification of Soils, the earth subgrade, the fixed track section, the corridor track, rubber plates, granulated gravel, the correlation coefficient. cators are read at 120 second intervals, and in the case of load-bearing layers this time may be reduced to 60 seconds. When measuring with 3 path indicators, the reading on the first indicator is taken 10 seconds before the waiting time ex- piry. The path indicators are always read in the same order and at identical time intervals. Load removal is carried out in 3 steps – 50 %, 25 % and 0 % of the maximum plate load. The second loading branch terminates in the last but one step of the first loading branch. The modulus of deformation (Verformungsmodul) is cal- culated from both the first and the second loading branch. It is determined from the loading chart, from the inclination of the secant line between two points given by the value of the 0.3- and 0.7-multiple of the maximum load, using the general formula: E r sv � � �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 in the 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 between the value of the 0.3- and 0.7-multiple of the maximum load [MPa]. 4 Measurement of moduli of deformation on rail bed models In order to establish the correlation between the moduli of deformation of rail bed structures determined in accordance with the Czech and German methodologies in laboratory conditions, the experimental box of the Department of Rail- way Structures of the Faculty of Civil Engineering, CTU in Prague was used. The experimental box consists of welded steel sections and removable walls of wooden planks. The walls of the box walls were lined with a thin galvanized plate to minimize the friction of the model at contacts with the walls of the box. The basic dimensions of the inside space of the experimental 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 while measuring the moduli of deformation on models in the experimental box. The experimental box was used for experimental moni- toring of 4 rail bed models in a 1:1 scale composed of rubber plates simulating earth subgrade with different bearing ca- pacities (10.9 MPa, 25 MPa), structural layers of granulated gravel of 0/32 mm grading with different thicknesses (15 cm, 30 cm) and a rail bed of gravel of 32/63 mm grading with a constant thickness of 35 cm. The gravel and granulated gravel were exposed to a grain composition test, which proved that the grain size composition of these materials is suitable for use in rail beds or in structural layers of the substructure body. The moduli of deformation were determined at three height levels: on a simulated earth subgrade, on a layer of granulated gravel and on a layer of gravel. The individual models were labelled with codes containing information on the thickness of the structural layer in cm, abbreviations of the 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 the experimental box is shown in Fig. 2. The structural layer was composed of either one or two layers, 150 mm in thickness, and the rail bed consisted of two layers, 175 mm in thickness. The individual layers were com- pacted with a special manual vibrating compacting device with a compacting area of 174×174 mm, and each layer was uniformly compacted for 30 minutes along the whole surface of the experimental box. © Czech Technical University Publishing House http://ctn.cvut.cz/ap/ 53 Czech Technical University in Prague Acta Polytechnica Vol. 46 No. 3/2006 Fig. 1: Measuring the static modulus of deformation on a granu- lated gravel layer in the experimental box Model labelling Earth subgrade bearing capacity in MPa Structural layer thickness in mm Rail bed thickness in mm 15SD E10 10.9 150 350 30SD E10 10.9 300 350 15SD E25 25.0 150 350 30SD E25 25.0 300 350 Table 1: Labelling of rail bed models and their characteristics 5 Measurements of moduli of deformation on a layer of gravel After each model, had been constructed, the three plate load tests on a layer of gravel were performed following the ČD methodology and then, in identical positions, three plate load tests were performed following the DB methodology. This measurement method was selected due to the confined plan of the model. Inaccuracy in determining of the modulus of deformation under the DB methodology, however, will be insignificant. The composition of the 15SD E10 model with schematic positions of the circular load plate is shown in Fig. 2. The determined values of the moduli of deformation are given in Table 2. 6 Measurements of moduli of deformation on a layer of granulated gravel Once the plate load tests on a layer of gravel were com- pleted, the gravel was removed from each model, and three plate load tests were performed on a layer of granulated gravel under the ČD methodology and subsequently, in iden- tical positions, three plate load tests were performed under the DB methodology. The determined values of the moduli of deformation are given in Table 3. 7 Measurements of moduli of deformation on sand The location selected for in-situ measurements of the moduli of deformation was the Klíčany sand pit, where sand with fine soil admixtures is quarried. The measurements were carried out at two points (field No. 1 and field No. 2) with the natural placement of sand layers showing no significant disintegration due to the extraction machinery. The counter- weight used during the measurement of the static moduli of deformation was a loaded lorry. In all, six plate load tests were performed using the ČD methodology and six plate load tests using the DB methodology. Once the plate load tests were completed, holes were dug at the measurement points to a depth of 1.0 m. These dug holes served for taking disinte- grated samples for geotechnical laboratory analyses which proved that the tested layer of sand can be classified under ČSN 72 1002 [5] as sand with fine soil admixtures (S3 S-F) with a mean natural moisture content of 7.8 % in field No. 1 and 5.5 % in field No. 2. The determined values of the moduli of deformation are given in Table 4. Fig. 3 shows the modulus of deformation being measured on a layer of sand in the Klíčany sand pit. 54 © Czech Technical University Publishing House http://ctn.cvut.cz/ap/ Acta Polytechnica Vol. 46 No. 3/2006 Czech Technical University in Prague a) b) Fig. 2: Rail bed structure model 15SD E10 in the experimental box: a) longitudinal section, b) cross section Model labelling Mean modulus of deformation in MPa ČD methodology DB methodology 15SD E10 63.8 71.3 30SD E10 79.4 98.3 15SD E25 90.0 104.5 30SD E25 103.9 117.7 Table 2: Moduli of deformation on a gravel surface for each methodology Model labelling Mean modulus of deformation in MPa ČD methodology DB methodology 15SD E10 26.1 23.0 30SD E10 53.3 48.9 15SD E25 50.1 44.1 30SD E25 82.9 86.4 Table 3: Moduli of deformation on a granulated gravel surface for each methodology 8 Measurements of moduli of deformation on soil The location selected for in-situ measurements of the moduli of deformation was the construction site of an em- bankment at Svojšovice as part of corridor IV within the Říčany – Stránčice section. The measurement was carried out on a compacted layer of highly non-homogeneous material compacted at two points (field No. 1 and field No. 2). The counterweight used was a flat vibratory roller or a loaded lorry. In all, six plate load tests were performed using the ČD methodology and six plate load tests using the DB metho- dology. Once the plate load tests were completed, holes were dug at the measurement points to a depth of 0.5 m. These dug holes served for taking disintegrated samples for geo- technical laboratory analyses which proved that the layer of soil can be classified under ČSN 72 1002 [5] as dirty gravel (G5 GC) to gravel with fine soil admixtures (G3 GF) with a mean natural moisture content of 12.7 % in field No. 1, while the soil layer in field No. 2 is composed of gravely clay (F2 CG) to gravely loam (F1 MG) with a mean moisture content of 15.8 %. The values of the moduli of deformation are shown in Table 5. 9 Correlation coefficients In order to express the relationship of the moduli of deformation determined under the ČD methodology and under the DB methodology, the correlation coefficients were calculated from the formula: k E E � DB ČD , where k is correlation coefficient [-], EDB modulus of deformation determined under the German methodology from the second loading branch [MPa], EČD modulus of deformation determined under the Czech methodology [MPa]. The correlation coefficients of the moduli of deformation on a layer of gravel are shown in Table 6, and on a layer of granulated gravel in Table 7. © Czech Technical University Publishing House http://ctn.cvut.cz/ap/ 55 Czech Technical University in Prague Acta Polytechnica Vol. 46 No. 3/2006 Fig. 3: Static modulus of deformation being measured on a layer of sand in the Klíčany sand pit Field labelling Mean natural moisture content in % Mean modulus of deformation in MPa ČD methodology DB methodology Field No. 1 8.7 82.2 136.8 Field No. 2 5.5 38.7 67.4 Table 4: Moduli of deformation on sand for each methodology Field labelling Mean natural moisture content in % Mean modulus of deformation in MPa ČD methodology DB methodology Field No. 1 12.7 92.1 66.3 Field No. 2 15.8 56.0 45.6 Table 5: Moduli of deformation on soil for each methodology The correlation coefficients of the moduli of deformation on sand are given in Table 8 and on soil in Table 9. 10 Conclusion The correlation coefficients determined in our experi- ment lead to the following conclusions: 1. The ČD and DB methodologies for measuring the static moduli of deformation apply the same testing apparatus (a circular load plate with a diameter of 30 cm), but the prescribed plate load loading is different and so is the calculation procedure for the static modulus of deformation. 2. Comparative measurements of static moduli of defor- mation show that the correlation dependency emerging from the determined moduli of deformation k � EDB/ EČD shows considerable differences both for different materi- als and for multi-layer systems of various materials. For example, the measurements revealed fluctuations in cor- relation coefficient “k” in the range of 0.76 to 1.70. In designing the track body, the values of the static moduli of deformation as determined under the ČD metho- dology and the DB methodology cannot be substituted for each other. 3. In designing the rail bed on SŽDC tracks, the require- ments for the load-bearing capacity of individual layers must be respected as regulated in instruction ČD S4 Sub- structure. The requirements given by instruction ČD S4 Substructure cannot be substituted for the requirements given by instruction DS 836 Vorschrift für Erdbauwerke applied by DB. 4. In the case of a potential change in the ČD methodology for measuring of the static modulus of deformation (e.g. by taking over a uniform European standard), instruction ČD S4 Substructure, ČSN 72 1006 Checking the compac- tion of soils and fills and other related regulations would have to undergo considerable modifications. 11 Acknowledgment This paper was written within the research project No. 1F52H/052/130 funded by Ministry of Transport of the Czech Republic. References [1] Krejčiříková, H., Tyc, P., Lidmila, M., Horníček, L., Voříšek, P., et al.: Methodology of Transitional Parameters for the Construction of Substructure and Tracks of the Conven- tional Trans-European System. Research reports of project 1F52H/052/130, Faculty of Civil Engineering, CTU in Prague, Department of Railway Structures, 2005 and 2006. [2] Instruction ČD S4 Substructure, 1997 (in force since 1. 7. 1998). [3] ČSN 72 1006 Checking the Compaction of Soils and Fills. Český normalizační institut, 1998. [4] DIN 18 134 Plattendruckversuch. Deutsches Institut für Normung e. V., 1993. [5] ČSN 72 1002 Classification of Soils for Transportation Structures. Český normalizační institut, 1993. Ing. Martin Lidmila, Ph.D. e-mail: lidmila@fsv.cvut.cz Ing. Leoš Horníček, Ph.D. e-mail: leos.hornicek@fsv.cvut.cz Doc. Ing. Hana Krejčiříková, CSc. phone: +420 224 354 756 e-mail: krejcirikova@fsv.cvut.cz Prof. Ing. Petr Tyc, DrSc. e-mail: petr.tyc@fsv.cvut.cz Department of Railway Structures Czech Technical University in Prague Faculty of Civil Engineering Thákurova 7 166 29 Praha 6, Czech Republic 56 © Czech Technical University Publishing House http://ctn.cvut.cz/ap/ Acta Polytechnica Vol. 46 No. 3/2006 Czech Technical University in Prague Model labelling Mean correlation coefficient “k” Total mean correlation coefficient “k” 15SD E10 1.12 1.17 30SD E10 1.24 15SD E25 1.16 30SD E25 1.13 Table 6: Correlation coefficients on a layer of gravel Model labelling Mean correlation coefficient “k” Total mean correlation coefficient “k” 15SD E10 0.88 0.94 30SD E10 0.92 15SD E25 0.88 30SD E25 1.04 Table 7: Correlation coefficients on a layer of granulated gravel Model labelling Natural moisture content in % Mean correlation coefficient “k” Total mean correlation coefficient “k” Field No. 1 12.7 0.72 0.76 Field No. 2 15.8 0.81 Table 9: Correlation coefficients on soil Model labelling Natural moisture content in % Mean correlation coefficient “k” Total mean correlation coefficient “k” Field No. 1 8.7 1.66 1.70 Field No. 2 5.5 1.74 Table 8: Correlation coefficients on sand