Results of laboratory researches of clay soil creepage according to regulations of N.N. Maslov's physicotechnical theory are stated. Tests were conducted at constant speed of deformation and continuous registration of vertical and horizontal deformations and pressure. Dependence of durability and creepage parameters from duration of preliminary condensation is established

Boley, K.

Strokova, L. А.

Electronic archive of Tomsk Polytechnic University

Research in creepage, long durability of clay soils isof exclusive value for designing various constructions.To describe the properties of clay soil flow various methods based on mechanical models, on the theory of hereditary creepage, the physicotechnical theory of creepage, the theory of plastic current, the molecular theory ofcurrent which are in details stated in S.S. Vyalov’s bookare applied [1]. As a result, all these theories lead to various equations of condition containing some parameters that are subject to experimental determination. Determination of flow parameters demands, on the onehand, complex equipment and technique of laboratoryand field tests, and on the other – calculation of the intensedeformed condition of soil massif in time by computer numerical methods. The experiments conductedby K. Tertsagi, S.S. Vyalov, M.N. Goldstein, N.N. Maslov, G.I. TerStepanyan, V.A. Florin, N.A. Tsytovich,S.R. Meschyan, Z.G. NerMartirosyan, U.K. Zaretsky,et al, showed that creepage of clay soils occurs both atvolumetric deformations and deformations of formchange (shift), often proceeding together [1, 2]. Dependence on pressure, deformation and time (the conditionequation) of clay soils is nonlinear. The process of soildeformation in time depends on the content of clayfractions, mineral hydrophility, soil density and humidity, drainage conditions, as well as on the value of operating normal and tangent pressures, and also duration ofshifting loading action, temperature, means and modeof load application [3–6].The purpose of the present research is to establishthe influence of duration of condensing loadings on parameters of durability and creepage.To determine these parameters the devices of oneplane section of WilleGeotechnik Company (Fig. 1)were used. The device provides onedimensional condensation of the sample vertically. Horizontal and vertical movements are fixed by digital indicators with theaccuracy of 0,001 mm. The distinctive feature of thisdevice is pressure and deformation digital registrationand storage of these data in a computer.The tests were conducted on clay samples of clay forthe dam body near Galdensleben (Germany). The basicparameters of granulometric composition, conditionand physical properties of soil are presented in Table 1.In accordance with GOST 2510095 – heavy softflexibility clay, by the Kazagrande classification highflexibility clay (Fig. 2).Table 1. Main characteristics of clayThree series of tests were conducted, at that variablemagnitudes were the size of normal loading and time ofits action. For error estimation the series of test wereconducted parallelly at three installations.The samples of identical density 1,75 g/sm3 and humidity 43,2 % were prepared for the tests. The identicaldensity was provided by constant mass of the ring244,5 g with ring area 70 sm2 and height 20 mm. Constant humidity was provided by accommodation of testsin special premise at constant temperature of 20 °С andair relative humidity of 100 %.The tests were conducted under the scheme «consolidateddrainage section». The value of vertical loadingswas taken as 100, 200, 400 kН/m2, the speed loading application was set equal to 10 kН/m2 per minute and wasmaintained then for 2880, 4320 and 8640 minutes. Aftercondensation, without unloading the device, the shiftwas conducted.The section was carried out at a constant sectionspeed in time γ. =0,02 mm/min – the socalled kinematic loading at which the tangent loading is applied continuously. The shift proceeded on the average for12...14 ours up to the maximal value of 15 mm.Each 10 seconds were registered during the tests:normal σ and tangential τ pressures, magnitude of vertical and horizontal deformations of the sample fromenclosed loading influence during condensation as wellas shift. The maximal (peak) τмах and the residual τresttangents of pressure, corners of internal friction ϕ andcohesion c at maximal and residual tangent pressure weParameter name ValueNatural humidity, % 43,2Density, g/sm3 1,780Density of oil particles, g/sm3 2,713Porosity, д.ед. 0,53Porosity coefficient, д.ед. 1,12Degree of watersaturation, д.ед. 0,95Top limit of plasticity, % 68,1Bottom limit of plasticity, % 19,5Number of plasticity, % 48,6Condensation parameter, д.ед. 0,51Content of clay fraction, % 62,3Content of dusty fraction, % 25,5Content of sand fraction, % 12,2Earth science39UDC 624.131.1DETERMINATION OF CLAY SOIL CREEPAGE CHARACTERISTICS K. Boley, L.A. StrokovaThe Military University, Munich, GermanyEmail: conrad.boley@unibw.de, ludmila.geyer@unibw.deResults of laboratory researches of clay soil creepage according to regulations of N.N. Maslov’s physicotechnical theory are stated. Testswere conducted at constant speed of deformation and continuous registration of vertical and horizontal deformations and pressure. Dependence of durability and creepage parameters from duration of preliminary condensation is established.re defined by the results of the test. The results of soilshift tests are shown in Table 2.Fig. 2. The Kazagrande graph for soil classification, •{ – the investigated soilExplanation to Fig. 2:Число пластичности – Number of plasticity Высокопластичнаяглина – Highflexibility clayГлина средней пластичности – Mediumflexibility clay Глинанизкопластичная – Lowflexibility clayВысокопластичные ил и органическая глина – Highflexibilitysilt and organic clayСреднепластичные ил и органическая глина – Mediumflexibility silt and organic clayПылеватая глина – Dusty clay Низкопластичный ил – Lowflexibility siltThe dependence of tangents pressure value on valueand duration of normal pressure is precisely stated byresults of the shift test. The increment of tangent pressure makes up 30...35 % at doubling of the enclosednormal pressures. The increase in duration of condensing loadings influence gives an increment of the maximal tangential pressure on 1,15...1,4 %.Table 2. Average values of oil shift tests resultsCondensation time, t, minAngle of internal friction,ϕ mахCohesion сmax, kН/m2Angle of internal friction,ϕ restCohe sion, сrest, kН/m2Normal exertion, σkН/m2Maxi mal tangen tial exertion, τ мах, kН/m2Residualexertion, τ rest, kН/m2Vertical deformation at shift,s 2, mmFull sedimentation at shift,s rest, mmSedimentation at condensation,s 1, mm2880 14,54 16,73 11,82 15,91100 42,28 36,85 0,16 0,31 2,11200 70,14 57,76 0,23 0,41 3,79400 122,71 99,71 0,25 0,38 5,064320 13,97 19,4 11,14 16,87100 42,80 35,94 0,12 0,29 2,51200 70,54 57,20 0,17 0,36 3,30400 124,15 95,31 0,20 0,37 5,018640 13,88 19,7 11,54 17,87100 43,17 36,24 0,16 0,28 1,32200 71,48 58,13 0,20 0,33 2,02400 127,48 100,3 0,23 0,37 5,11Bulletin of the Томsк Pоlytеchnic University. 2007. V. 310. № 240Fig. 1. The device for determination of compressibility and durability parameters made by Wille Geotechnik CompanyAfter shift completion the humidity from the shiftzone was defined. With increase of applied loading by100 kН/m2 oil humidity decreased respectively by4,2...4,6 % (Fig. 3).Fig. 3. Sample humidity change after the shiftDetermination of flow parameters was performed bythe Maslov’s technique [2, 5]. Schedules of soil horizontal deformation dependence from time λ=f(t) and growthof shearing effort τ in time were constructed based on testresults. Under schedules of dependence τ=f(t) Thethreshold of creepage τlim as well as crossing of tangents totwo curve sites (Fig. 4) was defined based on dependencies graph τ=f(t). The analysis of the constructed graphsshowed that with increase of sample preliminary condensation time the interval of time before sample destructiontкр under action of tangent pressures increases, thus thedifference τmax–τlim (Table 3) also decreases. The threshold of creepage comes to the maximal tangential pressure with time increase of the preliminary condensation.Fig. 4. Determination of creepage thresholdThe intensity of creepage process is estimated by coefficient of dynamic viscosity η calculated by N.N. Maslov’s formula [2. P. 138]:where τmax is the maximal (peak) tangential pressure atshift; τlim is the creepage threshold, γ. is the deformationspeed of sample shift equal to 0,02 mm/min; d is theheight of the sample before shift, mm. Results of creepage parameters determination are presented in Table 3.Table 3. Parameters of soil creepageVertical soil deformations at shift, socalled dilatancy is the phenomenon of material volume change caused by shift deformations, discovered in 1885 by O. Reynolds, was noticed at soil test by sensors.Thus, the obtained results of experimental researches showed that duration of condensing loading action before section renders essential influence on structure and properties of clays being reflected in parameters of durability and creepage. These results represented practical interest at forecast of landslide deformations and also at horizontal displacement of the projecteddam base.Time ofpreliminary condensation, minNormalpressure,kН/m2Durabilitythresholdat shift,τmax,кН/m2Creepagethreshold, τlim,кН/m2Dynamicviscositycoefficient, Pа·sShiftdeformation,λ, mmTimebeforesampledestruction, tкр,min2880100 42,28 38,18 2,22·108 2,64 124200 70,14 62,5 3,75·108 3,33 166400 122,71 117,5 2,35·108 4,31 2154320100 42,80 38,5 2,28·108 2,77 138200 70,54 67,3 1,64·108 3,57 178400 124,15 118,4 2,61·108 4,76 2388640100 43,17 41,8 7,76·107 3,31 169200 71,48 71,1 2,07·107 4,51 225400 127,48 126,6 3,65·107 5,77 288max lim ,dτ τη γ−= Tangential exertion, кН/м20510152025303540450 100 200 300 400 500ɍɩɥɨɬɧɹɸɳɚɹ ɧɚɝɪɭɡɤɚ, ɤɇ/ɦ2ȼɥɚɠɧɨɫɬɶ, %Humidity, %Condensing loading кН/м2Earth science41REFERNCES1. Vyalov S.S. Reologic fundamentals of soil mechanics. – Moscow:Vysshaya shkola, 1978. – 447 p.2. Maslov N.N. Physicotechnical theory of clay soil creepage in construction practice. – Moscow: Stroyizdat, 1984. – 175 p.3. Meschyan S.R. Initial and long durability of clay soils. – Moscow:Nedra, 1978. – 207 p.4. Meschyan S.R. Experimental reology of clay soils. – Moscow: Nedra, 1985. – 342 p.5. Recommendations at definition of soil creepage and consolidationparameters by laboratory methods / Product. and Scientific Research Institute on Engineering Research in Construction. – Moscow: Stroyizdat, 1989. – 59 p.6. TerMartirosyan Z.G. Reologic parameters of soil and calculationsof construction foundations – Moscow: Stroyizdat, 1990. – 199 p.Received on 12.12.2006

Determination of clay soil creepage characteristics

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