Geological nonhomogeneity of soils

Geological nonhomogeneity of soils

The nonhomogeneity of typical soils in Poland (Tertiary, Miocene and Pliocene clays, Quaternary glacial tills and loesses, Holocene fluvial sands) was analyzed in the paper. The analysis was limited to the presentation of the results of investigation of variability coefficient V and Kagan nonhomogen...

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Дата:2008
Автори: Kaczyński, R., Bąkowska, A.
Формат: Стаття
Мова:English
Опубліковано: Інститут прикладних проблем механіки і математики ім. Я.С. Підстригача НАН України 2008
Онлайн доступ:http://dspace.nbuv.gov.ua/handle/123456789/7695
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Цитувати:Geological nonhomogeneity of soils / R. Kaczynski, A. Bakowska // Приклад. пробл. механіки і математики. — 2008. — Вип. 6. — С. 207-211. — Бібліогр.: 9 назв. — англ.

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Digital Library of Periodicals of National Academy of Sciences of Ukraine
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spelling irk-123456789-76952010-04-09T12:01:05Z Geological nonhomogeneity of soils Kaczyński, R. Bąkowska, A. The nonhomogeneity of typical soils in Poland (Tertiary, Miocene and Pliocene clays, Quaternary glacial tills and loesses, Holocene fluvial sands) was analyzed in the paper. The analysis was limited to the presentation of the results of investigation of variability coefficient V and Kagan nonhomogeneity coefficient K1 determined for the basic parameters of lithological, microstructural, physical and mechanical properties used for designing the foundations of engineering objects. Nonhomogeneity of soils is determined by the geological conditions of their origin as well as by later changes. Проаналізовано неоднорідність типових ґрунтів на території Польщі. Аналіз обмежено до подання результатів дослідження зміни V, а також параметра змінності K1, визначених для основних літологічних мікроструктурних параметрів, і фізичних та механічних параметрів, які використовуються при проектуванні об’єктів. Неоднорідність ґрунтів зумовлена геологічними умовами, а також наступними змінами. Проанализирована неоднородность типовых почв на территории Польши. Анализ ограничен представлением результатов исследования изменения V, а также параметра K1, определяемых для основных литологических микроструктурных параметров, физических и механических свойств, используемых при проектировании объектов. Неоднородность почв обусловлена геологическими условиями, а также последующими изменениями. 2008 Article Geological nonhomogeneity of soils / R. Kaczynski, A. Bakowska // Приклад. пробл. механіки і математики. — 2008. — Вип. 6. — С. 207-211. — Бібліогр.: 9 назв. — англ. 1810-3022 http://dspace.nbuv.gov.ua/handle/123456789/7695 539.3 en Інститут прикладних проблем механіки і математики ім. Я.С. Підстригача НАН України
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
language English
description The nonhomogeneity of typical soils in Poland (Tertiary, Miocene and Pliocene clays, Quaternary glacial tills and loesses, Holocene fluvial sands) was analyzed in the paper. The analysis was limited to the presentation of the results of investigation of variability coefficient V and Kagan nonhomogeneity coefficient K1 determined for the basic parameters of lithological, microstructural, physical and mechanical properties used for designing the foundations of engineering objects. Nonhomogeneity of soils is determined by the geological conditions of their origin as well as by later changes.
format Article
author Kaczyński, R.
Bąkowska, A.
spellingShingle Kaczyński, R.
Bąkowska, A.
Geological nonhomogeneity of soils
author_facet Kaczyński, R.
Bąkowska, A.
author_sort Kaczyński, R.
title Geological nonhomogeneity of soils
title_short Geological nonhomogeneity of soils
title_full Geological nonhomogeneity of soils
title_fullStr Geological nonhomogeneity of soils
title_full_unstemmed Geological nonhomogeneity of soils
title_sort geological nonhomogeneity of soils
publisher Інститут прикладних проблем механіки і математики ім. Я.С. Підстригача НАН України
publishDate 2008
url http://dspace.nbuv.gov.ua/handle/123456789/7695
citation_txt Geological nonhomogeneity of soils / R. Kaczynski, A. Bakowska // Приклад. пробл. механіки і математики. — 2008. — Вип. 6. — С. 207-211. — Бібліогр.: 9 назв. — англ.
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fulltext ISSN 1810-3022. Ïðèêë. ïðîáëåìè ìåõ. ³ ìàò. – 2008. – Âèï. 6. – Ñ. 207–211. UDK 539.3 R. Kaczyński, A. Bąkowska GEOLOGICAL NONHOMOGENEITY OF SOILS The nonhomogeneity of typical soils in Poland (Tertiary, Miocene and Pliocene clays, Quaternary glacial tills and loesses, Holocene fluvial sands) was analyzed in the paper. The analysis was limited to the presentation of the results of investiga- tion of variability coefficient V and Kagan nonhomogeneity coefficient K1 determi- ned for the basic parameters of lithological, microstructural, physical and mecha- nical properties used for designing the foundations of engineering objects. Nonho- mogeneity of soils is determined by the geological conditions of their origin as well as by later changes. 1. Introduction. Soils are the subgrade for the majority of engineering structures. The subgrade is a part of the geological environment between the depth of foundation of the engineering object and the assumed range of prac- tical structure influence (0 3 zy zd ′σ = σ max. ). By its nature the subgrade built of various soils is a statistically unhomogeneous medium which is due primarily to original nonhomogeneity – geological origin, mainly sedimentation and con- solidation. The nonhomogeneity of soils can be intensified by later processes (factors) including those human-inducted. In solving concrete geotechnical and engineering geological problems the- oretical physical or mathematical models are applied. Parameters used in the- se models describing the physical and mechanical properties of soils and their behaviour under load are random values. Parameters used in engineering calculations e.g. when checking the limit state (load-bearing capacity and serviceability) are defined by the statistical analysis of field and laboratory results. The calculation parameter can be defi- ned only for a separate homogeneous soil layer. Therefore the crucial issue is to establish reliable homogeneity/nonhomogeneity criteria for soils. In building practice the standard coefficient of materials mγ is used to assess soil nonhomogeneity. In this case also the Kagan nonhomogeneity coef- ficient 1K can be taken into account (Table 1). Table 1. Nonhomogeneity of microstructural parameters of Pliocene clays from Warsaw Microstructural parameters R x σ V 1∆ mγ 1K Porosity n, % 37–52 43.94 3.86 0.09 8.1 0.91 0.48 Number of pores 310n ⋅ 0.8–347 87.66 106.42 1.21 259.3 – 0.41 Average pore diameter avD , µm 0.79–5.29 1.69 0.99 0.59 3.6 0.41 0.28 Total pore area 310tS ⋅ , 2mµ 27–1181 473.46 464.07 0.98 707.5 0.02 0.66 Average pore area avS , 2mµ 2.55–47.33 11.45 11.42 1.01 35.85 – 0.32 Total pore perimeter 310tP ⋅ , µm 27–2393 737.93 790.68 1.07 1655.1 – 0.48 Average pore perimeter 310avP ⋅ , µm 6.27–45.82 13.16 8.64 0.66 32.66 0.34 0.26 Average pore form index favK 0.432–0.599 0.51 0.05 0.09 0.089 0.91 0.56 Dominant orientation direction α °, 1.8–178.5 75.92 59.51 0.78 102.58 0.22 0.58 Microstructure anisotropy index aK , % 3.8–41.9 21.26 9.93 0.47 20.64 0.53 0.48 R – range of variability (R x x= −max min ), x – arithmetical mean, σ – standard deviation, V – variability coefficient, 1 x x∆ = −max , 1m Vγ = ± – 208 R. Kaczyński, A. Bąk standard coefficient of materials, 1 1/K = σ ∆ – Kagan nonhomogeneity coeffi- cient, 30N = – number of tests. The changeability (nonhomogeneity) of subgrade properties (parameters) is not always the same depends on microstructural and lithological (granulo- metric) features. Also soil parameters show a variable nonhomogeneity. In this paper analyzed are measures of nonhomogeneity mγ and 1K for various typical Polish soils including Tertiary clay, boulder clay and fluvial sands. Nonhomogeneities of various essential physical and mechanical soil pa- rameters are considered. 2. Characteristics of analyzed soils. Nonhomogeneity of the soils proper- ties is considered on the example of the following soils occurring in Poland: • Tertiary, Miocene and Pliocene clays; • Quaternary glacial tills, loesses and fluvial sands. The physical and mechanical properties of the clays were established du- ring their long and complicated geological history when they were subjected to several cycles of loading and unloading processes causing their overconsoli- dated state. The Tertiary (Miocene) clays from the Carpathian Foredeep (southern Poland) consist of marine, illitic and montmorillonitic, marly, laminated soils. These clays are very sensitive to exogenic factors. Due to cyclic drying/wet- ting processes they were passed from soils with very favourable properties to weathering waste with low strength parameters. The Tertiary (Pliocene) clays from the Warsaw area are generally quite monotonous. Their main components are clay minerals and quartz. Mineralogi- cal researches [2, 3, 5, 6, 7, 9] indicate that clay minerals are represented by mixed-packed minerals of beidellite-illite series. The Quaternary glacial tills are a typical result of glacial sedimentation. They include lodgement, melt-out and flow tills. They are composed of hete- rogeneous material and their composition depends on the rocks transported by the glacier from distant and nearby areas as well as the rocks taken from the glacier base. The tills contain quartz grains of various size as well as the grains of other rocks: gneiss, granite, quartzite, limestone. The sediment mat- rix is comprised of composition of fine grains calcite and particles of clay mi- nerals (illite or montmorillonite). Loesses represent a part of the sediments of Pleistocene origin. They are characterised by disordered texture and a carbonate content up to 10% CaCO3. Typical loesses have a silt structure. They exemplify eolic facies, un- weathered and mostly homogeneous, as it has been proved in various investi- gations. The Holocene fluvial sands deposited in rivers valleys are a product of mechanical crumbling of rocks by flowing water. The sedimentation of the material is very complex and depends mostly on the velocity and quantity of water in the river. Fluvial sediments almost always consist a composition of various fractions. The analyzed results concern the fluvial sands from the area of Warsaw. Mineral composition of these sands is monotonous – they mainly consist of feldspar and quartz grains. The sands are also characterized by va- riable compaction degree. 3. Nonhomogeneity of soils. Tables 1–3 present the results of soils inves- tigations. Nonhomogeneity of the tested soils are characterised by variability coefficient – V, standard coefficient of materials – mγ , Kagan’s nonhomoge- neity coefficient – 1K . Parameters describing the pore space of the Tertiary (Pliocene) clays re- veal a large nonhomogeneity. The coefficient V ranges between 9–121%, and 1 0.26 0.66K = − (Table 1). High values of V (sometimes above 100%) occur for: number of pores, average pore area, total pore perimeter. Geological nonhomogeneity of soils 209 Variability coefficient V for granulometric (lithological) composition of the tested soils presents following (Table 2): • Tertiary (Pliocene) clays 19 75%V = − ; 1 0.29 0.64K = − ; • glacial tills 37 101%V = − ; 1 0.32 0.60K = − ; • loesses 9 54%V = − ; 1 0.23 0.50K = − ; • fluvial sands 3 5%V = − ; 1 0.04 0.85K = − . Table 2. Lithological nonhomogeneity of various soils Type of soil Fraction content, % R x σ V 1∆ mγ 1K clayey < 0.002 mm 7.0–65.0 29.3 10.5 0.36 35.7 0.64 0.29 silty 0.002–0.05 mm 20.7–63.6 50.3 9.3 0.19 13.3 0.81 0.70 N = 6 36 P ia s- k ow sk i (1 96 3) sandy 0.05–2.0 mm 3.6–65.9 20.5 15.1 0.74 45.4 0.26 0.33 Clayey 28–89 56 19 0.34 33.0 0.66 0.58 Silty 11–64 37.5 17 0.46 26.5 0.54 0.64 P li oc en e cl ay N = 2 5 K B N (2 00 0) Sandy 0–29 6.5 8 0.75 22.5 0.25 0.36 Clayey 8–45 21.1 7.7 0.37 23.9 0.63 0.32 Silty 10–70 31.5 14.8 0.47 38.5 0.53 0.38 Sandy 2–78 45.0 19.6 0.44 33.0 0.56 0.60 B ou ld er cl ay N = 1 5 − 30 gravelly > 2.0 mm 0–10 2.4 2.4 1.01 7.6 – 0.32 Clayey 2–11 6.3 2.1 0.34 8.9 0.74 0.24 Silty 49–93 79.3 6.8 0.09 13.7 0.81 0.50 L oe ss N = 8 0 Sandy 2–47 14.2 7.6 0.54 32.8 0.46 0.23 clayey + silty 0–3 1.9 0.095 0.05 1.1 0.95 0.09 Sandy 92–100 95.5 3.82 0.04 4.5 0.96 0.85 S an d N = 5 0 Gravelly 0–4 2.21 0.066 0.03 1.79 0.97 0.04 Explanations according to Table 1. The nonhomogeneity of physical and mechanical properties is variable – the variability coefficient of physical parameters, generally, does not exceed 30–40%, whereas the same coefficient for strength and deformability parame- ters exceed 50%, and in the case of clays and tills even 100%. Very nonhomo- geneous parameter of analysed soils is the liquidity index (Table 3). Table 3a. Nonhomogeneity of the physical-mechanical parameters of various soils (explanations according to Table 1) Tertiary clay Parameter R x σ V 1∆ mγ 1K Specific density, Mg/m3 2.57–2.76 2.70 0.04 0.02 0.06 0.98 0.57 Volume density, Mg/m3 1.58–2.30 1.93 0.18 0.09 0.49 0.91 0.37 Volume density of soil skeleton, Mg/m3 1.18–2.04 1.51 0.23 0.15 0.53 0.85 0.43 Porosity, % 25.2–54.2 43.9 8.04 0.19 10.3 0.81 0.78 Natural water content, % 17.2–46.2 24.5 9.30 0.38 21.7 0.62 0.43 Liquidity limit, % 34.3–94.2 60.3 13.52 0.22 33.9 0.78 0.40 Plastic limit, % 14.0–41.0 33.5 8.67 0.26 7.5 0.74 >1 Plasticity index, % 18.9–53.2 33.5 7.0 0.21 19.7 0.79 0.36 Liquidity index –0.51–0.96 0.015 0.23 > 1 0.45 < 0 0.51 Angle of internal friction, ° 3.0–27.5 14.5 21.5 > 1 13 < 0 > 1 Cohesion, kPa 10–425 86 390 > 1 339 < 0 > 1 Modulus of compressibility, MPa 0.9–148 23 30 > 1 125 < 0 0.24 210 R. Kaczyński, A. Bąk Table 3b Boulder clay Parameter R x σ V 1∆ mγ 1K Specific density, Mg/m3 2.63–2.75 2.69 0.031 0.015 0.06 0.985 0.52 Volume density, Mg/m3 1.78–2.08 1.90 0.079 0.042 0.18 0.958 0.44 Volume density of soil skeleton, Mg/m3 1.48–1.85 1.62 0.035 0.022 0.23 0.98 0.15 Porosity, % 28.1–45.5 36.5 3.65 0.101 9.0 0.90 0.40 Natural water content, % 11.6–25.9 17.2 4.16 0.24 10.3 0.76 0.35 Liquidity limit, % 14.2–47.1 28.9 8.73 0.30 21 0.70 0.36 Plastic limit, % 11.9–20.7 15.4 3.15 0.20 6.7 0.80 0.43 Plasticity index, % 2.3–19.2 13.4 6.20 0.46 7.1 0.54 0.74 Liquidity index –0.31–0.65 0.13 0.20 > 1 0.52 < 0 0.38 Angle of internal friction, ° 6.0–25.5 11.8 5.0 0.42 14.5 0.58 0.28 Cohesion, kPa 0.5–43.5 24.0 9.1 0.38 18.5 0.62 0.48 Modulus of compressibility, MPa 5.1–35.6 12.5 21.35 > 1 23.1 < 0 0.92 Table 3c Loess Parameter R x σ V 1∆ mγ 1K Specific density, Mg/m3 2.64–2.71 2.68 0.02 0.01 0.03 0.99 0.33 Volume density, Mg/m3 1.35–2.05 1.77 0.12 0.07 0.28 0.93 0.43 Volume density of soil skeleton, Mg/m3 1.20–1.71 1.50 0.08 0.05 0.21 0.95 0.38 Porosity, % 32.9–57.6 41.0 3.8 0.09 17.6 0.91 0.22 Natural water content, % 7.2–21.9 12.5 3.0 0.24 9.8 0.76 0.31 Liquidity limit, % 23.8–27.3 25.5 0.8 0.04 1.8 0.96 0.44 Plastic limit, % 18.6–24.7 20.6 1.3 0.07 4.1 0.93 0.32 Plasticity index, % 1.0–6.5 4.9 1.3 0.27 1.6 0.73 0.81 Liquidity index, - – < 0 – – – – – Angle of internal friction, ° 15–31 25 4.5 0.18 6 0.82 0.75 Cohesion, kPa 10–90 35 15 0.43 55 0.57 0.27 Modulus of compressibility, MPa 0.39–5.0 2.01 0.94 0.46 2.99 0.54 0.31 Table 4. Criteria for determining of soil nonhomogeneity in terms of the variability coefficient V [%] for various parameters Parameter Author C la y f ra ct io n co n te n t S p ec if ic d en si ty V ol u m e d en si ty of n at u ra l so il V ol u m e d en si ty of t h e so il s k el et on P or os it y N at u ra l w at er c on te n t L iq u id it y l im it P la st ic l im it P la st ic it y i n d ex L iq u id it y i n d ex A n g le o f in te rn al fr ic ti on C oh es io n M od u lu s of co m p re ss ib il it y Ingles O. [4] – – 3 – 25 – 10 10 30 – 10 30 30 Biernatowski K. [1] – – 2.5 – 30 – 15 10 20(30) – 5(15) 12.5–30 5–20 Kagan A. [8] – – – 3 – – 20 20 – – – – – Proposal 25 2 3 5 25 20 20 20 25 50 20 20–40 50 4. Assessment of soil nonhomogeneity. The assessment of nonhomogene- ity may be made using various criteria, often basing on the limit values of the variability coefficient – V. The limit values which can be found in the litera- ture are given in Table 4. Different authors assume different values of V for particular parameters. The new criteria of nonhomogeneity of the properties of soils have been proposed taking into account the literature data, author’s experience, accuracy of the testing methods and natural variability of soils. Geological nonhomogeneity of soils 211 5. Conclusions. It should be emphasised that, generally, the soils are non- homogeneous media. Nonhomogeneity of soils is affected by the origin and la- ter changes, including the anthropogenic ones. 1. Nonhomogeneity of soils is mainly determined by granulometric and mi- neral composition and by their microstructures. 2. Soil nonhomogeneity depends on the various impurities, inclusions, and concretions. Variable consolidation and occurrence of weakened surfaces are also of great importance. 3. The highest nonhomogeneity has been noted in cohesive soils (clays and boulder clays). More homogeneous are loose soils. 4. Particular values are characterised with uniform values of variability co- efficient V. High values of coefficient V and Kagan nonhomogeneity coef- ficient 1K are revealed mainly in mechanical and deformability parame- ters: moduli, cohesion, angle of internal friction and liquidity index. 5. Considering engineering geological properties, for the purposes of engine- ering calculations, the analysed soils may be classified as the homogene- ous ones, characterised by a value of the variability coefficient the limit value. The proposed limit values of V are presented in the Table 4. We would like to thank the Dean of Geology Faculty of Warsaw University (BW–2006) for allowing us to contact the hereby survey. 1. Biernatowski K. Statystyczna charakterystyka środowiska geologiczno-inżyniers- kiego // Mat. Konf. «Metody statystyczne w geotechnice»: Prace Nauk. Inst. Geo- tech. Politechniki Wrocławskiej. – Wrocław, 1984. – 44. – P. 5–12. 2. Dobak P. Problemy oceny jednorodności ośrodka gruntowego na podstawie zmien- ności wybranych parametrów geotechnicznych // Ibid. – P. 23–30. 3. Frankowski Z., Kaczyński R., Bogucki A., Wołoszyn A. Nonhomogeneity of the phy- sical-mechanical properties of soil medium composed of Tertiary clays and Quater- nary loesses // J. Theor. and Appl. Mech. (Warsaw). – 1998. – 3, No. 36. – P. 1–14. 4. Ingles O. G. Soil variability, construction quality, control and performance reliabili- ty // Proc. University of New South Wales. – Sydney, 1979. – P. 1–49. 5. Kaczyński R. Geological nonhomogeneity of the subgrade // Proc. 1st Ukr.-Polish Sci. Symp. «Mixed problems of the mechanics of nonhomogeneous structures» (Lviv – Shack, 1995). Sbornik Naucznych Rabot. – 1997. – 36, No. 2. – P. 30–36. 6. Kaczyński R. Lithological and microstructural nonhomogeneity of Warsaw Mio- Pliocene clays // Ïðèêë. ïðîáëåìè ìåõàí³êè ³ ìàòåìàòèêè. – 2003. – Âèï. 1. – Ñ. 169–177. 7. Kaczyński R., Trzciński J. Microstructural nonhomogeneity of glacial tills // ³ñí. Ëüâ³â. óí-òó. Ñåð. ìåõ.-ìàò. – 1999. – Âèï. 55. – Ñ. 152–157. 8. Kagan A. A. Computational characteristics of soils. – Ìîñêâà: Ñòðîéèçäàò, 1985. (In Russian). 9. Trzciński J., Kaczyński R. Nonhomogeneity of the physical properties of glacial tills // ³ñí. Ëüâ³â. óí-òó. Ñåð. ìåõ.-ìàò. – 1999. – Âèï. 55. – Ñ. 158–160. ГЕОЛОГІЧНА НЕОДНОРІДНІСТЬ ҐРУНТІВ Ïðîàíàë³çîâàíî íåîäíîð³äí³ñòü òèïîâèõ ´ðóíò³â íà òåðèòî𳿠Ïîëüù³. Àíàë³ç îá- ìåæåíî äî ïîäàííÿ ðåçóëüòàò³â äîñë³äæåííÿ çì³íè V, à òàêîæ ïàðàìåòðà çì³í- íîñò³ K1, âèçíà÷åíèõ äëÿ îñíîâíèõ ë³òîëîã³÷íèõ ì³êðîñòðóêòóðíèõ ïàðàìåòð³â, ³ ô³çè÷íèõ òà ìåõàí³÷íèõ ïàðàìåòð³â, ÿê³ âèêîðèñòîâóþòüñÿ ïðè ïðîåêòóâàíí³ îá’ºêò³â. Íåîäíîð³äí³ñòü ´ðóíò³â çóìîâëåíà ãåîëîã³÷íèìè óìîâàìè, à òàêîæ íà- ñòóïíèìè çì³íàìè. ГЕОЛОГИЧЕСКАЯ НЕОДНОРОДНОСТЬ ПОЧВ Ïðîàíàëèçèðîâàíà íåîäíîðîäíîñòü òèïîâûõ ïî÷â íà òåððèòîðèè Ïîëüøè. Àíàëèç îãðàíè÷åí ïðåäñòàâëåíèåì ðåçóëüòàòîâ èññëåäîâàíèÿ èçìåíåíèÿ V, à òàêæå ïàðàìåòðà K1, îïðåäåëÿåìûõ äëÿ îñíîâíûõ ëèòîëîãè÷åñêèõ ìèêðîñòðóêòóðíûõ ïàðàìåòðîâ, ôèçè÷åñêèõ è ìåõàíè÷åñêèõ ñâîéñòâ, èñïîëüçóåìûõ ïðè ïðîåêòèðî- âàíèè îáúåêòîâ. Íåîäíîðîäíîñòü ïî÷â îáóñëîâëåíà ãåîëîãè÷åñêèìè óñëîâèÿìè, à òàêæå ïîñëåäóþùèìè èçìåíåíèÿìè. Warsaw Univ., Warsaw, Poland Received 11.03.08

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