Climate�Impact�Forecasting�for� Slopes Slope�Remediation�� Current�Practice Stuart�Hardy ���
Contents�of�Talk • What�Do�We�Do? • Why�Do�We�Do�It? • How�Do�We�Do�It? • The�Future�For�Slope�Stability�Assessment • Questions�We�Would�Like�To�Raise ���
Contents�of�Talk • What�Do�We�Do? • Why�Do�We�Do�It? • How�Do�We�Do�It? • The�Future�For�Slope�Stability�Analysis • Questions�We�Would�Like�To�Raise ���
What�Do�We�Do? We�work�for�all�the�major�earthwork�infrastructure� • owners British�Waterways – Network�Rail – London�Underground�Limited – Highways�Agency – ���
Contents�of�Talk • What�Do�We�Do? • Why�Do�We�Do�It? • How�Do�We�Do�It? • The�Future�For�Slope�Stability�Assessment • Questions�We�Would�Like�To�Raise ���
Why�Do�We�Do�It? Interruption�of� • services Emergency�works • High�costs • Loss�of�revenue • Loss�of�customers • ���
Contents�of�Talk • What�Do�We�Do? • Why�Do�We�Do�It? • How�Do�We�Do�It? • The�Future�For�Slope�Stability�Assessment • Questions�We�Would�Like�To�Raise ���
How�Do�We�Do�It? 1. Inspection�of�earthworks�&�risk�assessment 2. Detailed�investigation�and�design�of�stabilisation�measures 3. Applied�research�projects ���
1.�Earthwork�Inspections • Each�operator�has�developed�their�own�system – Network�Rail�(RT/CE/S/065) – LUL�(E�3735) – HA�(HD�41/03) ���
2.�Detailed�Analysis • Limit�Equilibrium�Techniques�to�Assess�Stability ���
2.�Detailed�Design • Contiguous�Bored�Pile�Wall ���
2.�Detailed�Design • Soil�Nailing ���
2.�Detailed�Design • Gabion�Walls/Reinforced�Earth ���
2.�Detailed�Design • None�of�the�inspection�standards�fully�address�the� influence�of�vegetation�on�slope�stability�or� vulnerability�to�seasonal�rainfall�effects • None�of�the�commonly�used�design�methods�can� take�account�of�the�effect�of�vegetation�or�seasonal� rainfall�effects ���
3.�Research�Projects • LUL�Research�Stage�II�– Assessment�of�Cuttings�and� Embankments�(LUL) • Queensbury�Instrumented�Embankment�(LUL) • Seasonal�Preparedness�(NR) • The�Effect�of�Vegetation�on�Slope�Stability�(RSSB) ���
Contents�of�Talk • What�Do�We�Do? • Why�Do�We�Do�It? • How�Do�We�Do�It? • The�Future�For�Slope�Stability�Assessment • Questions�We�Would�Like�To�Raise ���
The�Future�For�Slope�Stability� Assessment • Extended�Use�of�SMD�for�risk�assessment Rainfall SMD ���
The�Future�For�Slope�Stability� Assessment� • Use�of�more�advanced�analysis�tools – Finite�Element/Difference • ���������������������������� • ����������������������� ��� ���
CHASM�– Modelling�rainfall�effects�on����������� slope�pore�pressures • CHASM�can�be�used�to�model�the�effect�of�any� combinations�of�rainfall�events�on�the�stability�of�a� slope Reduction in Suctions with Time pore pressure (m) -10 -8 -6 -4 -2 0 2 4 0 depth below slope surface (m) 0.5 1 10 days 1.5 2 15 days 2.5 ��� 20 days 3 25 days 3.5
CHASM�– Modelling�rainfall�effects�on����������� slope�pore�pressures Reduction in FoS from Initial Value 110% F o S a s % o f b a s e lin e 100% 90% 80% 70% 0 5 10 15 20 25 30 time (days) ���
Progressive�Failure • FLAC�can�be�used�to�model�the�effect�of�vegetation� on�progressive�failure Winter�– Embankment� Swells ���
Progressive�Failure Track� Winter�– Heaves Embankment� Swells ���
Progressive�Failure Winter�– Plastic�Strains� Embankment� Develop�at�toe Swells Φ peak Φ residual ���
Progressive�Failure Zero�Pore�pressure�line Low�Pore�Water� Summer�– Pressures Embankment� Shrinks ���
Progressive�Failure Track� Summer�– Settles Embankment� Shrinks ���
Progressive�Failure Plastic�Strains�Not� Summer�– Recovered Embankment� Shrinks Φ peak Φ residual ���
Progressive�Failure Continued� Cycling ���
Progressive�Failure Continued� Cycling ���
Progressive�Failure Failure! ���
Questions�We�Would�Like�to�Raise • Can�we�gain�a�better�understanding�of�the�interaction�of� climate�and�vegetation�with�slope�behaviour? • Can�this�be�engineered�to�positively�benefit�a�slope? • Can�Soil�Moisture�Deficit�be�modified�to�take�account�of�slope� orientation�and�slope�angle�when�making�the�risk�assessment� for�a�certain�slope? • Will�this�greater�understanding�allow�us�to�move�away�from� hard�structural�solutions�like�bored�piles/soil�nails? ���
��� www.mottmac.com
Life�expired�embankments On�going� • deformation Speed�restrictions • Expensive� • maintenance Unpredictable�costs • Dissatisfied� • customers ���
1.�Earthwork�Inspections • Inspection�procedures�take�into�account – Slope�geometry�(angle�and�height) – Observations�of�water�(seepage,�ponding) – Evidence�of�instability�(bulges,�tension�cracks�or�crooked�trees) • Condition�rating� – Serviceable,�marginal�or�poor�for�LUL�and�NR�procedure� – Class�1,�2,�or�3�for�HA • Crude�Risk�Assessment – Inspection�regime – Remediation�of�slope ���
2.�Detailed�Analysis • LUL�Design�Standards – For�a�London�Clay�Embankment – Foundation�Material:� φ � =�21°,� � ‘ =�2kPa� γ =�19�kN/m 3 – Embankment�Material:� φ � =�21°,� � ‘ =�1kPa� γ =�19�kN/m 3 – Four�options�available�for�pore�pressure�conditions – For�slope�covered�with�mature�trees,�the�pore�pressure�is� hydrostatic�below�zero�pressure�line�which�is�assumed�2m�below� surface – Track�loading�of�30kPa�applied�from�sleeper�end�to�sleeper�end ���
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