OR/12/032 Geohazards - Revision history

Ajhil: /* General */

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General

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	==Sulphate==		==Sulphate==
	===General===		===General===
	Sulphates and sulphides are very common in British stratigraphic formations, occurring naturally in a variety of forms in mudstones and other sediments, including Lias Group mudstones and clays. The distribution and classification of sulphate in British rocks and soils is described in BRE Digest 363 (Building Research Establishment, 1991<ref name="Building Research Establishment 1991">BUILDING RESEARCH ESTABLISHMENT. 1991. Sulphate and acid resistance of concrete in the ground. Building Research Establishment, BRE Digest 363. </ref>; 1996<ref name="Building Research Establishment 1996">~~Building Research Establishment~~. 1996. Sulphate and acid resistance of concrete in the ground. Building Research Establishment, BRE Digest 363.</ref>) and Forster et al. (1995)<ref name="Forster 1995">FORSTER, A, CULSHAW, M G, and BELL, F G. 1995. Regional distribution of sulphate in rocks and soils of Britain. In: Eddleston, M, Walthall, S, Cripps, J C, and Culshaw, M G (editors). Engineering Geology of Construction. ''Geol. Soc. Spec. Publ''. No. 10, pp.95–104. </ref>. Typically, sulphate content varies with depth and weathering state. The damaging effects of sulphate salts on concrete, particularly below the water table, are well documented. For example, during construction of the M40 motorway in Oxfordshire, England, heave of the carriageway was caused when lime stabilisation of pyrite-bearing Charmouth Mudstone Formation (formerly the ‘Lower Lias Clay’) was attempted. The layer concerned had to be removed (Anon, 1991b<ref name="Anon 1991b">ANON 1991b. Soil lime reaction causes M40 heave. ''Ground Engineering'', Jan/Feb 1991, 8. </ref>).		Sulphates and sulphides are very common in British stratigraphic formations, occurring naturally in a variety of forms in mudstones and other sediments, including Lias Group mudstones and clays. The distribution and classification of sulphate in British rocks and soils is described in BRE Digest 363 (Building Research Establishment, 1991<ref name="Building Research Establishment 1991">BUILDING RESEARCH ESTABLISHMENT. 1991. Sulphate and acid resistance of concrete in the ground. Building Research Establishment, BRE Digest 363. </ref>; 1996<ref name="Building Research Establishment 1996">BUILDING RESEARCH ESTABLISHMENT. 1996. Sulphate and acid resistance of concrete in the ground. Building Research Establishment, BRE Digest 363.</ref>) and Forster et al. (1995)<ref name="Forster 1995">FORSTER, A, CULSHAW, M G, and BELL, F G. 1995. Regional distribution of sulphate in rocks and soils of Britain. In: Eddleston, M, Walthall, S, Cripps, J C, and Culshaw, M G (editors). Engineering Geology of Construction. ''Geol. Soc. Spec. Publ''. No. 10, pp.95–104. </ref>. Typically, sulphate content varies with depth and weathering state. The damaging effects of sulphate salts on concrete, particularly below the water table, are well documented. For example, during construction of the M40 motorway in Oxfordshire, England, heave of the carriageway was caused when lime stabilisation of pyrite-bearing Charmouth Mudstone Formation (formerly the ‘Lower Lias Clay’) was attempted. The layer concerned had to be removed (Anon, 1991b<ref name="Anon 1991b">ANON 1991b. Soil lime reaction causes M40 heave. ''Ground Engineering'', Jan/Feb 1991, 8. </ref>).

	The best-known forms of sulphate in mudrocks are gypsum and anhydrite formed by the oxidation of sulphides. Sulphides, particularly pyrite (FeS<sub>2</sub>), are formed in anaerobic conditions through the action of sulphate-reducing bacteria and are generally found as dispersed microscopic minerals. Pyrite oxidation is complex but may be summarised as follows:		The best-known forms of sulphate in mudrocks are gypsum and anhydrite formed by the oxidation of sulphides. Sulphides, particularly pyrite (FeS<sub>2</sub>), are formed in anaerobic conditions through the action of sulphate-reducing bacteria and are generally found as dispersed microscopic minerals. Pyrite oxidation is complex but may be summarised as follows:

Ajhil: /* Inland landslides */

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Inland landslides

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	The influence of weathering on slope stability has been examined by Chandler (1972)<ref name="Chandler 1972">CHANDLER, R J. 1972. Lias clay: weathering processes and their effect on shear strength. </ref>. Sites at Culworth, Stowehill, Gretton, and Rockingham (Northamptonshire), and at Wothorpe (near Stamford, Lincolnshire) were studied for relationships between degree of weathering and strength, in the light of landslides and cambers at the sites. The author noted that persistent instability of a road cut at Wothorpe appeared to be related to fabric disturbance of the Whitby Mudstone Formation, probably associated with cambering of the overlying ironstone (Northampton Sand Formation), and linked it with similar observations in the Bath and Wellingborough areas. The author also proposed a weathering scheme for the Whitby Mudstone Formation (Upper Lias Clay) (Chandler, 1972<ref name="Chandler 1972"></ref>). Periglacial freeze/thaw effects on the Lias have been described (Kovacevic et al., 2007<ref name="Kovacevic 2007">KOVACEVIC, N, HIGGINS, K G, POTTS, D M, and VAUGHAN, P R. 2007. Undrained behaviour of brecciated Upper Lias Clay at Empingham Dam. ''Geotechnique'', 57, No. 2, pp.181–195.</ref>). These have resulted in a distinctive brecciated fabric and highly variable geotechnical properties ([[OR/12/032 Weathering #Physical weathering \|''see'' Physical weathering]]).		The influence of weathering on slope stability has been examined by Chandler (1972)<ref name="Chandler 1972">CHANDLER, R J. 1972. Lias clay: weathering processes and their effect on shear strength. </ref>. Sites at Culworth, Stowehill, Gretton, and Rockingham (Northamptonshire), and at Wothorpe (near Stamford, Lincolnshire) were studied for relationships between degree of weathering and strength, in the light of landslides and cambers at the sites. The author noted that persistent instability of a road cut at Wothorpe appeared to be related to fabric disturbance of the Whitby Mudstone Formation, probably associated with cambering of the overlying ironstone (Northampton Sand Formation), and linked it with similar observations in the Bath and Wellingborough areas. The author also proposed a weathering scheme for the Whitby Mudstone Formation (Upper Lias Clay) (Chandler, 1972<ref name="Chandler 1972"></ref>). Periglacial freeze/thaw effects on the Lias have been described (Kovacevic et al., 2007<ref name="Kovacevic 2007">KOVACEVIC, N, HIGGINS, K G, POTTS, D M, and VAUGHAN, P R. 2007. Undrained behaviour of brecciated Upper Lias Clay at Empingham Dam. ''Geotechnique'', 57, No. 2, pp.181–195.</ref>). These have resulted in a distinctive brecciated fabric and highly variable geotechnical properties ([[OR/12/032 Weathering #Physical weathering \|''see'' Physical weathering]]).

	Landslides feature on the Lincolnshire Limestone Formation and Marlstone Rock Formation escarpments of the East Midlands, for example in the Grantham area (Forster, 1992<ref name="Forster 1992">~~Forster~~, A. 1992. The slope stability of the Lincolnshire limestone escarpment between Welbourne and Grantham. 1:50 000 Geological Map sheet 127. ''British Geological Survey'' Technical Report WN/92/5.</ref>; Berridge et al., 1999<ref name="Berridge 1999">BERRIDGE, N G, PATTISON, J, SAMUEL, M D A, BRANDON, A, HOWARD, A S, PHARAOH, T C, and RILEY, N J. 1999. Geology of the country around Grantham. ''Memoir British Geological Survey''. Sheet 127 (England and Wales).</ref>), Melton Mowbray area (Carney et al., 2002<ref name="Carney 2002">CARNEY, J N, AMBROSE, K, and BRANDON, A. 2002. Geology of the Melton Mowbray district: a brief explanation of the geological map Sheet 142, Melton Mowbray. ''British Geological Survey''. NERC.</ref>), and on the Lincoln Scarp (Penn et al., 1983<ref name="Penn 1983">PENN, S, ROYCE, C J, and EVANS, C J. 1983. The Periglacial modification of the Lincoln Scarp. ''Quarterly Journal of Engineering Geology'' 16 pp. 309–318.</ref>). Shallow slumps and mudflows characterise slope instability within the underlying Whitby Mudstone Formation between Grantham and Lincoln, and also to the southwest of Grantham bordering the Vale of Belvoir. These become readily re-activated and result in a hummocky surface. Cambering of the Marlstone Rock Formation has also been observed in the Grantham area (Berridge et al., 1999<ref name="Berridge 1999"></ref>). In Rutland there are scattered landslides on the Whitby Mudstone Formation, between Uppingham and Oakham. Further south, landslides have been investigated at Rockingham, near Corby [at SP 874 918 and between SP 874 918 and 889 925] (Chandler, 1972<ref name="Chandler 1972"></ref>). In the Market Harborough area, there are shallow landslides of shallow successive rotational slide type within the Whitby Mudstone Formation overlain by Northampton Sand Formation at Medbourne [SP 803 933] (Figure 5.8) and Slawston Hill [SP 782 941] (Poole et al., 1968<ref name="Poole 1968">POOLE, E G, WILLIAMS, B J, and HAINS, B A. 1968. Geology of the country around Market Harborough. ''Memoir of the Geological Survey of Great Britain'', explanation of sheet 170 (England and Wales). HMSO, London. </ref>).		Landslides feature on the Lincolnshire Limestone Formation and Marlstone Rock Formation escarpments of the East Midlands, for example in the Grantham area (Forster, 1992<ref name="Forster 1992">FORSTER, A. 1992. The slope stability of the Lincolnshire limestone escarpment between Welbourne and Grantham. 1:50 000 Geological Map sheet 127. ''British Geological Survey'' Technical Report WN/92/5.</ref>; Berridge et al., 1999<ref name="Berridge 1999">BERRIDGE, N G, PATTISON, J, SAMUEL, M D A, BRANDON, A, HOWARD, A S, PHARAOH, T C, and RILEY, N J. 1999. Geology of the country around Grantham. ''Memoir British Geological Survey''. Sheet 127 (England and Wales).</ref>), Melton Mowbray area (Carney et al., 2002<ref name="Carney 2002">CARNEY, J N, AMBROSE, K, and BRANDON, A. 2002. Geology of the Melton Mowbray district: a brief explanation of the geological map Sheet 142, Melton Mowbray. ''British Geological Survey''. NERC.</ref>), and on the Lincoln Scarp (Penn et al., 1983<ref name="Penn 1983">PENN, S, ROYCE, C J, and EVANS, C J. 1983. The Periglacial modification of the Lincoln Scarp. ''Quarterly Journal of Engineering Geology'' 16 pp. 309–318.</ref>). Shallow slumps and mudflows characterise slope instability within the underlying Whitby Mudstone Formation between Grantham and Lincoln, and also to the southwest of Grantham bordering the Vale of Belvoir. These become readily re-activated and result in a hummocky surface. Cambering of the Marlstone Rock Formation has also been observed in the Grantham area (Berridge et al., 1999<ref name="Berridge 1999"></ref>). In Rutland there are scattered landslides on the Whitby Mudstone Formation, between Uppingham and Oakham. Further south, landslides have been investigated at Rockingham, near Corby [at SP 874 918 and between SP 874 918 and 889 925] (Chandler, 1972<ref name="Chandler 1972"></ref>). In the Market Harborough area, there are shallow landslides of shallow successive rotational slide type within the Whitby Mudstone Formation overlain by Northampton Sand Formation at Medbourne [SP 803 933] (Figure 5.8) and Slawston Hill [SP 782 941] (Poole et al., 1968<ref name="Poole 1968">POOLE, E G, WILLIAMS, B J, and HAINS, B A. 1968. Geology of the country around Market Harborough. ''Memoir of the Geological Survey of Great Britain'', explanation of sheet 170 (England and Wales). HMSO, London. </ref>).

	[[Image:OR12032fig5.8.jpg\|thumb\|center\|500px\| '''Figure 5.8'''    Active shallow successive landslides in Whitby Mudstone Formation at Medbourne, Leics. (Feb 2003) [SP803 933]. ]]		[[Image:OR12032fig5.8.jpg\|thumb\|center\|500px\| '''Figure 5.8'''    Active shallow successive landslides in Whitby Mudstone Formation at Medbourne, Leics. (Feb 2003) [SP803 933]. ]]

Ajhil: /* Sulphate attack of concrete */

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Sulphate attack of concrete

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	===Sulphate attack of concrete===		===Sulphate attack of concrete===
	Thaumasite (derived from the Greek word ‘thaumasion’ meaning surprising) may be formed by sulphate attack on concrete and has been found on twenty to thirty year old concrete structures on the M5 and other major trunk roads in Gloucestershire, Somerset and Wiltshire, in the Charmouth Mudstone Formation. Of the concrete structures investigated 75% had been damaged, with abutments and columns being the most severely affected members. In each case Charmouth Mudstone Formation backfill had been used. There has been some confusion in the past regarding the classification schemes, based on the different sulphate tests described in BS1377:1990<ref name="BS1377 1990">~~British Standards~~: BS 1377. 1990. Methods of test for soils for civil engineering purposes. British Standards Institution, BS1377. </ref>, their precision, and their relationship to TSA (Longworth, 2004<ref name="Longworth 2004"></ref>). In the majority of cases, the sulphate class limits based on soil extract tests were both lower than sulphate class based on sulphate in groundwater and were also low when compared to the actual occurrence of TSA. The new limits given in BRE Special Digest 1 bring sulphate classification based on 2:1 water/soil extract tests into parity with the groundwater based tests.		Thaumasite (derived from the Greek word ‘thaumasion’ meaning surprising) may be formed by sulphate attack on concrete and has been found on twenty to thirty year old concrete structures on the M5 and other major trunk roads in Gloucestershire, Somerset and Wiltshire, in the Charmouth Mudstone Formation. Of the concrete structures investigated 75% had been damaged, with abutments and columns being the most severely affected members. In each case Charmouth Mudstone Formation backfill had been used. There has been some confusion in the past regarding the classification schemes, based on the different sulphate tests described in BS1377:1990<ref name="BS1377 1990">BRITSH STANDARDS: BS 1377. 1990. Methods of test for soils for civil engineering purposes. British Standards Institution, BS1377. </ref>, their precision, and their relationship to TSA (Longworth, 2004<ref name="Longworth 2004"></ref>). In the majority of cases, the sulphate class limits based on soil extract tests were both lower than sulphate class based on sulphate in groundwater and were also low when compared to the actual occurrence of TSA. The new limits given in BRE Special Digest 1 bring sulphate classification based on 2:1 water/soil extract tests into parity with the groundwater based tests.

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Ajhil: /* Inland landslides */

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Inland landslides

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	[[Image:OR12032fig5.5.jpg\|thumb\|center\|500px\| '''Figure 5.5'''    Landslides and Lias Group strata in the Cotswolds (southern section).<br>[Key: grey = Lower Lias, yellow = Middle Lias, purple = Upper Lias, hatching = landslide]. ]]		[[Image:OR12032fig5.5.jpg\|thumb\|center\|500px\| '''Figure 5.5'''    Landslides and Lias Group strata in the Cotswolds (southern section).<br>[Key: grey = Lower Lias, yellow = Middle Lias, purple = Upper Lias, hatching = landslide]. ]]
	Whilst the landslides mainly date from times of periglacial conditions, some areas are currently active, and examples in the Lias occur at Broadway (Rowlands et al., 2003<ref name="Rowlands 2003">		Whilst the landslides mainly date from times of periglacial conditions, some areas are currently active, and examples in the Lias occur at Broadway (Rowlands et al., 2003<ref name="Rowlands 2003">
			ROWLANDS, K A, JONES, L D, and WHITWORTH, M. 2003. Landslide laser scanning: a new look at an old problem. ''Quarterly Journal of Engineering Geology & Hydrogeology''. Vol. 36, Part 2, pp.155–157.</ref>; Whitworth et al., 2003<ref name="Whitworth 2003"></ref>), Moreton-in-Marsh, and around Cheltenham. The principal (though not the only) mode of slope failure in the Lias Group is as shown in Figure 5.6 taken from Butler (1983)<ref name="Butler 1983">BUTLER, P B. 1983. Landsliding and other large scale mass movements on the escarpment of the Cotswold Hills. ''BA Thesis (unpublished) Hertford College, Oxford''.</ref>:
	~~Rowlands~~, K A, ~~Jones~~, L D, and ~~Whitworth~~, M. 2003. Landslide laser scanning: a new look at an old problem. ''Quarterly Journal of Engineering Geology & Hydrogeology''. Vol. 36, Part 2, pp.155–157.</ref>; Whitworth et al., 2003<ref name="Whitworth 2003"></ref>), Moreton-in-Marsh, and around Cheltenham. The principal (though not the only) mode of slope failure in the Lias Group is as shown in Figure 5.6 taken from Butler (1983)<ref name="Butler 1983">BUTLER, P B. 1983. Landsliding and other large scale mass movements on the escarpment of the Cotswold Hills. ''BA Thesis (unpublished) Hertford College, Oxford''.</ref>:

	[[Image:OR12032fig5.6.jpg\|thumb\|center\|500px\| '''Figure 5.6'''    Mass movement processes in the Cotswolds (modified after Butler, 1983<ref name="Butler 1983"></ref>). ]]		[[Image:OR12032fig5.6.jpg\|thumb\|center\|500px\| '''Figure 5.6'''    Mass movement processes in the Cotswolds (modified after Butler, 1983<ref name="Butler 1983"></ref>). ]]

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Inland landslides

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	''Cotswold Hills''<br>		''Cotswold Hills''<br>
	The Cotswold Hills are well known for their escarpments, outlier hills, and the many examples of landslides and cambering associated with them (Goudie & Parker, 1996<ref name="Goudie 1996">GOUDIE, A S, and PARKER, A G. 1996. The geomorphology of the Cotswolds. Cotteswolds Naturalists’ Field Club</ref>; Jones & Lee, 1994<ref name="Jones 1994"></ref>; Whitworth et al., 2003<ref name="Whitworth 2003">WHITWORTH, M, GILES, D, and MURPHY, W. 2003. Landslides of the Cotswold Escarpment, Broadway, Worcestershire UK. ''Proc. Cotteswold Naturalists Field Club''. XLII (II).pp.118–127.</ref>; Seedhouse, 1987<ref name="Seedhouse 1987">~~Seedhouse~~, R L. 1987. Lias clay slopes in the Evesham area: a general assessment of slope stability. M.Sc Thesis, Dept. of Geology, ''Imperial College'', London.</ref>). To the south, the Great Oolite is the main scarp-forming caprock and the Fuller’s Earth Formation (Great Oolite Group) provides a weak underlying mudstone. To the north, however, the Inferior Oolite becomes the main caprock and the Lias Group mudrocks the substrate. Landslide frequency is strongly influenced by this change in geology, which occurs in the area of Stroud; the frequency increasing from south to north (Figures 5.3, 5.4 and 5.5).		The Cotswold Hills are well known for their escarpments, outlier hills, and the many examples of landslides and cambering associated with them (Goudie & Parker, 1996<ref name="Goudie 1996">GOUDIE, A S, and PARKER, A G. 1996. The geomorphology of the Cotswolds. Cotteswolds Naturalists’ Field Club</ref>; Jones & Lee, 1994<ref name="Jones 1994"></ref>; Whitworth et al., 2003<ref name="Whitworth 2003">WHITWORTH, M, GILES, D, and MURPHY, W. 2003. Landslides of the Cotswold Escarpment, Broadway, Worcestershire UK. ''Proc. Cotteswold Naturalists Field Club''. XLII (II).pp.118–127.</ref>; Seedhouse, 1987<ref name="Seedhouse 1987">SEEDHOUSE, R L. 1987. Lias clay slopes in the Evesham area: a general assessment of slope stability. M.Sc Thesis, Dept. of Geology, ''Imperial College'', London.</ref>). To the south, the Great Oolite is the main scarp-forming caprock and the Fuller’s Earth Formation (Great Oolite Group) provides a weak underlying mudstone. To the north, however, the Inferior Oolite becomes the main caprock and the Lias Group mudrocks the substrate. Landslide frequency is strongly influenced by this change in geology, which occurs in the area of Stroud; the frequency increasing from south to north (Figures 5.3, 5.4 and 5.5).

	[[Image:OR12032fig5.3.jpg\|thumb\|center\|500px\| '''Figure 5.3'''    Landslides and Lias Group strata in the Cotswolds (northern section).<br>[Key: grey = Lower Lias, yellow = Middle Lias, purple = Upper Lias, hatching = landslide]. ]]		[[Image:OR12032fig5.3.jpg\|thumb\|center\|500px\| '''Figure 5.3'''    Landslides and Lias Group strata in the Cotswolds (northern section).<br>[Key: grey = Lower Lias, yellow = Middle Lias, purple = Upper Lias, hatching = landslide]. ]]

Ajhil: /* Inland landslides */

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Inland landslides

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	Whilst the landslides mainly date from times of periglacial conditions, some areas are currently active, and examples in the Lias occur at Broadway (Rowlands et al., 2003<ref name="Rowlands 2003">		Whilst the landslides mainly date from times of periglacial conditions, some areas are currently active, and examples in the Lias occur at Broadway (Rowlands et al., 2003<ref name="Rowlands 2003">

	Rowlands, K A, Jones, L D, and Whitworth, M. 2003. Landslide laser scanning: a new look at an old problem. ''Quarterly Journal of Engineering Geology & Hydrogeology''. Vol. 36, Part 2, pp.155–157.</ref>; Whitworth et al., 2003<ref name="Whitworth 2003"></ref>), Moreton-in-Marsh, and around Cheltenham. The principal (though not the only) mode of slope failure in the Lias Group is as shown in Figure 5.6 taken from Butler (1983)<ref name="Butler 1983">~~Butler~~, P B. 1983. Landsliding and other large scale mass movements on the escarpment of the Cotswold Hills. ''BA Thesis (unpublished) Hertford College, Oxford''.</ref>:		Rowlands, K A, Jones, L D, and Whitworth, M. 2003. Landslide laser scanning: a new look at an old problem. ''Quarterly Journal of Engineering Geology & Hydrogeology''. Vol. 36, Part 2, pp.155–157.</ref>; Whitworth et al., 2003<ref name="Whitworth 2003"></ref>), Moreton-in-Marsh, and around Cheltenham. The principal (though not the only) mode of slope failure in the Lias Group is as shown in Figure 5.6 taken from Butler (1983)<ref name="Butler 1983">BUTLER, P B. 1983. Landsliding and other large scale mass movements on the escarpment of the Cotswold Hills. ''BA Thesis (unpublished) Hertford College, Oxford''.</ref>:

	[[Image:OR12032fig5.6.jpg\|thumb\|center\|500px\| '''Figure 5.6'''    Mass movement processes in the Cotswolds (modified after Butler, 1983<ref name="Butler 1983"></ref>). ]]		[[Image:OR12032fig5.6.jpg\|thumb\|center\|500px\| '''Figure 5.6'''    Mass movement processes in the Cotswolds (modified after Butler, 1983<ref name="Butler 1983"></ref>). ]]

Ajhil at 09:15, 6 August 2021

2021-08-06T09:15:44Z

Show changes

Ajhil: /* Sulphate attack of concrete */

2021-08-03T12:28:27Z

Sulphate attack of concrete

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	{\| class="wikitable"		{\| class="wikitable"
	<span id="Table 5.4"></span>		<span id="Table 5.4"></span>
	\|+ Table 5.4    Table of Lias Group sulphate medians with new classification based on SO<sub>4</sub> (aqueous extract) test data: medians and maxima.		\|+ Table 5.4    Table of Lias Group sulphate medians with new classification<br>based on SO<sub>4</sub> (aqueous extract) test data: medians and maxima.
	\|- style="vertical-align:top;"		\|- style="vertical-align:top;"
	\| style="background-color: #dcdcdc;" \| '''Formation'''		\| style="background-color: #dcdcdc;" \| '''Formation'''

Ajhil: /* Lias Group shrink/swell behaviour */

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Lias Group shrink/swell behaviour

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	{\| class="wikitable"		{\| class="wikitable"
	<span id="Table 5.2"></span>		<span id="Table 5.2"></span>
	\|+ Table 5.2    Results of ~~3-D~~ swelling strain test; values represent maxima.		\|+ Table 5.2    Results of 3D swelling strain test; values represent maxima.
	\| style="background-color: #dcdcdc;" \|		\| style="background-color: #dcdcdc;" \|
	\| style="background-color: #dcdcdc;" \|		\| style="background-color: #dcdcdc;" \|

Ajhil: /* Lias Group shrink/swell behaviour */

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Lias Group shrink/swell behaviour

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	The degree of over-consolidation or induration of the several Lias Group mudstones vary, and this variation imparts different shrink/swell behaviour and anisotropy, other factors being equal. Over-consolidation tends to result in greater lateral than vertical volume change. Increased induration tends to reduce the amount of overall volume change due to improved stiffness and the development of cementation. Weathering tends to have the reverse effect, whereby stiffness and stress-related anisotropy are reduced, thus tending to increase shrink/swell movement in the vertical plane.		The degree of over-consolidation or induration of the several Lias Group mudstones vary, and this variation imparts different shrink/swell behaviour and anisotropy, other factors being equal. Over-consolidation tends to result in greater lateral than vertical volume change. Increased induration tends to reduce the amount of overall volume change due to improved stiffness and the development of cementation. Weathering tends to have the reverse effect, whereby stiffness and stress-related anisotropy are reduced, thus tending to increase shrink/swell movement in the vertical plane.

	A small number of swelling and shrinkage tests were carried out on Lias Group samples by BGS and reported in Hobbs et al. (2007)<ref name="Hobbs 2007"></ref>. The results of one particular test, the ~~3-D~~ swell strain test, are summarised in Table 5.2. These show that the more thinly bedded and shaly specimens within (e.g. All Blue Lias; Whitby Mudstone, Sidegate Lane 1) produced greater swell strain anisotropy (up to 8 x) in a 50 mm cube-shaped specimen at natural initial water content, than more uniform, non-shaly or thicker bedded, specimens (e.g. Charmouth Mudstone, Blockley Site 1; Whitby Mudstone, Brixworth 1).		A small number of swelling and shrinkage tests were carried out on Lias Group samples by BGS and reported in Hobbs et al. (2007)<ref name="Hobbs 2007"></ref>. The results of one particular test, the 3D swell strain test, are summarised in Table 5.2. These show that the more thinly bedded and shaly specimens within (e.g. All Blue Lias; Whitby Mudstone, Sidegate Lane 1) produced greater swell strain anisotropy (up to 8 x) in a 50 mm cube-shaped specimen at natural initial water content, than more uniform, non-shaly or thicker bedded, specimens (e.g. Charmouth Mudstone, Blockley Site 1; Whitby Mudstone, Brixworth 1).

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