Physical modelling of rainfall induced landslides under
controlled climatic conditions
A. Askarinejad, J. Laue, A. Zweidler, M. Iten, E. Bleiker, H. Buschor, S.M. Springman
Institute for Geotechnical Engineering, ETH Zurich, SwitzerlandAbstract: A series of small scale physical modelling tests are performed in a geotechnical drum centrifuge in order to investigate the triggering mechanisms of landslides due to rainfall. They are conducted under controlled conditions of rainfall intensity and duration, ambient relative humidity, wind, and temperature. These tests have been designed to study the possible failure mechanisms proposed for a full scale landslide experiment. Accordingly, different shapes and hydraulic properties of the bedrock, in terms of drainage and exfiltration, are provided for the model. A three dimensional close range photogrammetric technique is used to track the movements and monitor the volumetric changes of the ground during the cycles of wetting and drying. The slope elevation is filmed during and following the rainfall events using a high speed camera and the deformation vectors and strains are elaborated using the PIV method. Details of the design of the climate chamber are discussed in this paper.
Keywords: Landslides, rainfall, bedrock, exfiltration, physical modelling, climate chamber.
1
INTRODUCTION
Landslides induced by rainfall impose considerable damage to infrastructure and cause major casualties worldwide. Several attempts have been undertaken to investigate the triggering mechanisms of these frequent and often powerful natural hazards. These studies were done using analytical approaches, numerical simulations and also physical modelling techniques. The physical modelling of landslides due to rainfall covers the wide range of full scale testing (e.g. Harp et al., 1990, Moriwaki et al., 2004, Ochiai et al., 2004) to smaller scale laboratory experiments under 1g conditions (e.g. Eckersley, 1990, Wang & Sassa, 2003, Picarelli et al., 2006) or under increased acceleration using centrifuges (e.g. Kimura et al., 1991, Take et al., 2004, Ling et al., 2009, Hudacsek et al., 2009, Ling et al., 2010). Many different aspects of the problem have been addressed but less emphasis has been put on the hydro-mechanical interactions between the bedrock and the soil slope.
Accordingly, a climate chamber has been designed and constructed at the Institute for Geotechnical Engineering at the Swiss Federal Institute of Technology in Zurich (ETHZ). This work is performed in the framework of the TRAMM project (Triggering of RApid Mass Movements1). Two landslide experiments were conducted in October 2008 and March 2009 on a 38° steep slope on the east facing banks of the river Rhine in northern Switzerland near the village of Ruedlingen (Springman et al., 2010, Askarinejad et al., 2012). An amount of about 1500 mm rainfall was sprinkled over the slope within 4.5 days (including 1 day drying period) during the first experiment with more concentration on the lower part where large fissures in the bedrock were detected. No failure was observed in the slope after this extreme event, although the whole profile of the soil cover had very low values of suction and piezometers showed slight increases (maximum of 170 mm) in the water table. According to the probing results conducted all around the test field, the bedrock is longitudinally parallel to the surface but laterally inclined. The depth of the bedrock varied between 0.5 m to more than 5 m. A convex bulge was identified in the lower part of the slope, which may have a stabilising effect. The shape of the bedrock is
1
illu fis dra up ex 13 gro fis wa an Fig and aff soi (sh ex an of
2
Th 44 ma tab sev rel als Zu ustrated in ssures, espe ainage netw pper part of periment. In 0 m3 lands oundwater ssured rock ater was ex nd less veget gure 1. Shap d different fecting the st A series il mass duri hape and p filtration fr nd hydrogeo the designGEOT
he geotechn 40 g and cap ain channel ble is locate A new t veral electr lative move so connectin urich geotec Figure 1. G cially, in th work in stab the slope w n this test, r slide. The p table above in the uppe filtrating fr tation effect pe of the bed mechanical tability of the s of centrifu ing cycles o permeability om the bed ological inte of differentTECHNIC
nical drum c pacity of 88 l by means ed in the mid tool table ha rical and da ements durin ng them wit chnical drum Geological i he lower pa bilizing the where less ro rainfall with piezometers e the bedro er part of therom the bac ts, this exfil drock in the R and hydrog e slope (after uge tests ha of wetting a y of the be drock) mech eractions be t parts of the
CAL DRU
centrifuge o 80 ton.g. Th of two 700 ddle and ca as been des ata transfer ng the tests th chains as m centrifuge investigatio art of the sloslope durin oot reinforc h a total am s located in ck. These m e slope. Mo ck of the fa ltrated wate Ruedlingen e geological m r Brönnimann as been star and drying a drock) and hanisms of R tween the s e constructe
UM CENT
of the ETH Z he channel h 0 mm squar n rotate eith signed for th r devices. T s. This is as s a backup s e is shown i ons revealed ope. These ng the first cement and mount of 22 n the failed measuremen oreover, bas ailure wedge er might hav experiment mechanisms nn, 2011). rted to inve and also to d triggering Ruedlingen slope and th ed climate cTRIFUGE
Zurich has has a volum re infill sup her together his series o Therefore, t ssured by co system to lim in Figure 2 w d the existe fissures mi t experimen shallower b 25 mm with d area show nts can be sed on the p e (Figure 1 ve been a ke Figure 2. G Zurich with estigate the study differ (loss of su experimen he bedrock a chamber areE AT ET
a diameter me of 1.45 m pport plates r with the ch of tests, and the channe oupling the mit potentia with the raince of an i ight have fu nt. Rainfall bedrock wer in 15 hours wed signific attributed to photographs ). Together ey factor in Geotechnical h the rain sim
hydro-mech rent hypothe uction due ts. The effe are studied e explained i
H ZURIC
of 2.2 m, m m3. Strong b (Springma hannel or at d it hosts the l and the t channel an al differenti n simulator interconnec functioned a was conce re expected s was enoug cant rises ( to the shallo s taken durin r with shall destabilisin l drum cent mulator setup hanical beh eses about t to rain inf ects of the b in these tes in this contrCH
maximum a boxes are in an et al., 20 t a different e main wat tool table m nd tool table ial moveme r setup. ted system as an efficie ntrated in t in the seco gh to trigger (~1 m) in t ower and le ng the failu ower bedro ng the slope trifuge at ET p. haviour of t the stabilisi filtration, a bedrock sha sts. The stag ribution. cceleration nstalled in t 001). The to speed. er supply a must have e together a ents. The ET of ent the ond r a the ess ure, ock e. TH the ing and ape ges of the ool and no and TH3
SCALING LAWS
The scaling laws for the infiltration of rainfall into the soil mass and the resultant laws for the rain intensity and duration will be determined in this section. Moreover, the scaling law for static liquefaction, as a possible triggering mechanism of fast landslides, is discussed.
3.1 Scaling law for the infiltration and rainfall specifications (macroscopic)
According to Darcy’s law, the seepage velocity ( ) in a porous medium between two points is proportional to the hydraulic gradient ( ) between them. The constant of this proportionality is called hydraulic conductivity ( ). As established by Schofield (1980), the seepage velocity is N times higher in the model under Ng centrifugal acceleration. Accordingly, the seepage time will be N2 times less than the prototype, as the seepage length is N times shorter in the model. Therefore, the duration of the rainfall in the N times scaled down model will also be N2 times less than that of the prototype. The length equivalent of the total precipitated rainfall in the model will be N times less than that of the prototype and the rain intensity (which is a ratio between the total rain and the rain duration) will be N times higher in the model. Other scaling laws are discussed in the next section and summarized in Table 1.
Table 1. Scaling laws for the rainfall parameters, infiltration process and static liquefaction.
Term [Dimension] Prototype Model
Length (macroscopic) [L]
Seepage velocity (macroscopic & microscopic) [L/T] Seepage time (macroscopic) [T]
Total rain [L] Rain duration [T] Rain intensity [L/T] Length (particle scale) [L] Seepage time (microscopic) [T]
Hydraulic gradient (macroscopic) [L/L] Hydraulic gradient (microscopic) [L/L]
1 1 1 1 1 1 1 1 1 1 1/N 1/N2 1/N 1/N2 N 1 1/N N N
3.2 Scaling laws for the static liquefaction mechanism (microscopic)
One of the commonly proposed mechanisms of fast landslides triggered by rainfall is static liquefaction. Static liquefaction is generally defined as the loss of strength of the loose contractive material under undrained conditions (Olson et al., 2000, Chu et al., 2003, Casini et al., 2010). The internal mechanism leading to static liquefaction can be explained by the collapse of saturated voids which may result in local and abrupt increase of the pore pressure (Take et al., 2004). Consequently, this locally increased pore pressure reduces the shear strength and can trigger movements in the soil mass. This chain of events may lead to the general instability of the slope.
The main focus is on the structure of the soil used in modelling the static liquefaction process, and if similar structure is reproduced in the model using the same material as that in the prototype, the scaling factor of the length (L) in this particle size scale will be Lp/Lm=1 (The subscripts p and m stand for
prototype and model, respectively). This assumption is based on the fact that the structure of the soil in these series of centrifuge tests will be reproduced by preparation of the models with a given initial water content and void ratio, although ‘younger’ reconstituted models normally have larger voids compared to the natural samples.
The time scale for gravitational falling (Timpact) of a particle would be:
, , 1 , m 1, m impact m impact p p impact p T L a L T N a L a T N (1)
where L is the falling height, and a is the acceleration. In this equation it is assumed that the particle falls in the air medium and the drag force is negligible. The impact of the falling of a particle on a saturated void causes a sudden increase of the pore fluid pressure. The velocity of dissipation of this generated
ex (T (Fi co be H sat Fig ver mo fas A V 1 pro po to Ho soi fri
4
Th me a r wi sho cess pore p aylor, 1995 igure 3) w nductivity o calculated , p f A p f h H where, H turated pore gure 3. a) sch rtical directio The hyd odel and the ster in the m AB A B AB H k D It is con 1⁄ , while ototype. Th ore pressure use a pore owever, Bec il with visc ction angleTHE B
he main go echanisms o rain simulat ith different ould be take pressure ca 5) but with will be gove of the medi using equat , , f p p f W H S H is the tot e, is the u hematic of th on c) concep draulic cond e prototype model comp , B A B m B V ncluded that e the localis herefore, it i dissipates e fluid √ ck, (2011), cose pore fl .BASIC C
oal of the c of landslide tor has bee t durations en into cons an be calcu scaling fact erned by th ium. The to tion (2). , 0 , B p H H al hydraulic unit weight he slope b) m ptual model u ductivity an , according pared to the A AB N H k D t under Ng sed dissipat is inferred 1⁄ faste times mor based on a luid, concluONCEPT
climate cha es due to rai n designed according t sideration w ulated using tor of 1 for he hydrauli tal hydrauli , p f A m f h H c head, W i of the pore microstructur under Ng acc nd the distan ly the seepa prototype: , B p A N V acceleratio tion of the that increas er than the c re viscous t a series of s uded that thT OF THE
mber is to infall and hy that enable to the scali when planni g Darcy’s the drainag ic gradient ic head (H) , f m m f W S is the weigh fluid at 1g, re of the soil celeration. nce betwee age and the, dissipa B p dissip T T
on, the impa excess por sed accelera collapse of t than water saturated an he soil with
E CLIMA
provide th ydro-mecha es the user ing laws. T ing applicat law (simila ge length). T between th at points A p N N h S ht of the fa , and S is th l-pores show en the point e pore pressu , , 1 ation m ation p N act time of re fluid pre ation provid the soil struto reduce nd unsaturat h a viscose
ATE CHA
he possibili anical intera to apply di he size of t ion of the ra ar to the co The flow of hese two p A and B in m p f W N H alling partic e cross sect wing particle ts A and B ure dissipat a particle i essure will des a condit ucture. Ther the dissipa ted direct sh fluid has mAMBER
ty to inves actions with ifferent rain the droplets ainfall. onsolidation f fluid from points and model and , , , A p B m H H cle, h is the tion area of impacting an are tion time w is reduced b N times fa ition in whi refore, it is r ation time i hear tests o marginally l stigate seve h the bedroc n intensities s and the C n phenome m point A to the hydrau prototype c 0 (2) height of t the pore. nother one in similar in t will be N tim (3) by a factor aster than t ich the exce recommend in the mod on Ruedling lower intern eral triggeri ck. Therefo s on the slo Coriolis Effe ena o B ulic can the n a the mes of the ess ded del. gen nal ing re, ope fectmm 10 int mo 31 pre cer we wh oc an of flo wh Th res tw inf Fig po me ph co the
5
Th pip a c cap The size m in diamet 000 mm is tensities wh odel rain dr .4 to 54.9 m The rain edefined he rtain distan ere conducte hich was d currence of nd rain inten the slope. In the dr ow and incre hich is insta hese two va sistance wir wo points ov formation to gure 4. The c Measurin ore pressure echanical an hotogramme llapse of th The cham e spinning oRAIN
he rain simu pes, water c cylindrical pacity of 24 e of the rain ter for heav measured f hen perform rops are sca microns in d nfall is ap eights above nce to the so ed to invest determined f surface flo nsity. An ef rying phase ease in the a alled in the d alves open a re coil to he ver the slope o control th conceptual sc ng the soil e fluctuation nalysis of r etric method e soil struct mber should of the centriSIMULA
ulator of thi channels gro aluminium 4.6 litres. T n drops in a vy rain and for light ra med at 50g i aled 50 time diameter. plied over e the slope oil, the fine tigate the m to be 70 to ow is depen fficient drain of the tests ambient tem direction of and close t eat the air. T e and these e evaporatio chematic of t movements ns, are the rainfall indu ds are used ture during d also be co ifuge. The cATOR AN
s climate ch ooved into t container t he water in prototype v squalls, dep ain (<1 mm in the tests es smaller t the slope surface to r e particles o minimum dis o 100 mm ndent on the nage system s, it is neces mperature. T f the centrifu ogether. Th The relative measureme on process. the climate c s and volum key aspect uced landsli d in these te the wetting ompletely ai climate chamND THE T
hamber is c the top plate that is insta the CWT i varies from pending on m/hr) (Tama of this stud than the reaby means reduce the of the soil c stance from , depending e difference m with filte ssary to con The air flow fugal rotatio he pipe con e humidity ents, togeth chamber with metric chang ts in unsatu ides. Accor ests to mon g and drying ir tight to av mber is illus
TOOL TA
composed o es of the ch alled in the is pressurise m 300 micron the rain int ate et al., 2 dy are more al rain drop s of non-un Coriolis eff can be wash the nozzles g on the n between th r layers is r ntrol the pro w is provided n and the ot nnected to t and temper er with the h dimensions ges of the so urated soil rdingly, Par nitor the mo g cycles.void the eff strated in Fi
ABLE
f a central w hamber, and middle of ed by a sma ns for fine d ensity. The 2010). How e than 1 mm s of an inte niformly d fect. If the n hed out. Th s to the soil ozzle type he hydraulic required to ocess of eva d by means ther facing he inlet val ature of the suction bui s in centimetr oil microstr mechanics rticle Image ovements an fects of the t igure 4. water tank ( the nozzles the tool tab aller air tankdrizzles to m e range of 3 wever, the p m/hr and ac ense rainfall distributed n nozzles are herefore, a surface to a and rain i c permeabil avoid pond aporation by of two air v in the oppo lve is cover e chamber i ild up in the tres. ructure, tog and the co e Velocime nd possible turbulent ai (CWT), ma s (Figure 5) ble on a pla k to 10 bar more than 2 00 microns prototype ra ccordingly t l and they a nozzles, w closer than series of te avoid erosio intensity. T lity of the s ding at the t y means of valves, one osite directio red by a hi s measured e soil, provi ether with t oupled hydr try (PIV) a swelling a r flows due gnetic valv ). The CWT atform with and regulat 2.6 to ain the are ith n a sts on, The oil toe air of on. igh d at ide the ro-and and to es, T is h a ted
by rea Th the cen wa are ch gro no esp sep Mo (Sc tes no int wa Fig mo co inv fro ins ins ins tra y a valve w aches the no The wat his sensor is ese two poi ntre of the ater level ar The wat e connected ambers, wh The pip ooved to pr ozzles and t pecial epox parate chan oreover, the chofield, 19 Differen sted careful ozzles are d tensities ba ater from th gure 5. Wa ounted on the The wat nvey it to vestigated. om outside stalled only stalled on th The hub stalled on t ansmitted in 1 http://hag with an outp ozzles. ter height in s connected ints. Since tank (125 rising from t ter flow from d to two T-v hich are inst
es are conn rovide two s the outer ch xy glue and nnel system e large num 980). nt types of lly to check determined sed on thes he CWT dur ater supply e tool table. er is distrib the back o Two infra-r during the y for safety he drum and b of the pho the tool tab nflight throu go.danfoss.co put pressure n the CWT to the top a the connec mm from t the increase m the CWT valves. Hig talled comp nected to th systems of c hannel to 1 d several scr provides th mber of nozz Hago mini k that they at differen se data. The ring the test
system to uted from t of the bedr red cameras tests. Thes reasons. Th d transmitte otogrammet ble, the latt ugh a wirele om/ e at 2.5 bar T is monitor and bottom ction of the the centre), e in the cent T is controll gh pressure letely diame he top plat channels for 8 outer noz rews along he possibilit zles provide misting no are function nt pressures e applied ra s. the climat he T-valves rock of the s are also in se cameras he data from ed to the con try cameras ter is bene ess connecti rs to ensure red by a pr of the CWT sensor to , the results trifugal acce led by mean pipes conv etrically op tes of the c r the water zzles (Figur the channe ty of apply es flexibility ozzles1 are ning proper s and the n ain intensit te chamber s via Water e models in nstalled on cannot obs m these cam ntrol room b s and the c eath the pla ion to the co e there is e ressure diffe T and measu the bottom s should be eleration. ns of two m ey the wate pposite to ea chamber. Th flow. The in re 6). The t els to make ing 3 differ y to limit th used. Befo rly. The sp nozzles are ty is also ca Figure 6. with the tw Distributio n which th the tool tab serve the re meras are se by slip rings computer to atform of th ontrol room enough wat ference sens
ures the diff part of CW e corrected magnetic wa er from the ach other in he inner pa nner channe two plates e them com rent rain int he effect of ore each tes ray angle a e selected t alculated ba
The top plat wo channel s
on Boxes (W he exfiltratio
ble to monit esponse of ent via vide s and remot o store the d he CWT. T . ter pressure sor (PDS- K fference in t WT is not e according ater valves. tool table t the centrifu art of the u el is connec are attache mpletely wat tensities du the Corioli st, all of th and discharg to deliver ased on the tes of the cl system for ra WDB) into f on from th tor the clim the soil mo eo server to
te desktop c data for the The capture e as the wat Keller PD1 the pressure exactly at t to the curv These valv to the clima uge channel upper plate cted to 4 inn d together ter tight. Th uring the tes
s accelerati he nozzles a ge rate of t different ra e flow rate imate chamb infall supply four pipes th he bedrock mate chambe odels and a the comput connection. e pictures a ed photos a ter 1). e at the ved ves ate l. is ner by his sts. ion are the ain of ber y. hat is ers are ter are are
6
An lay in et on on fro dra Ke be Fig hy7
7.1 PD mo wh rel eq PP ap en Ho air flu suc sen eq Fig loc cuBEDR
n aluminium yer for the sthe overlyi al., 2011) a n the top sur ne hand, wa om the bedr ained throug The top eller 2MIX tween the b gure 7. The draulic intera
INSTR
1 Pore wa DCR81 PPT onitor both hen they ar lative to the quilibrium q PTs were sa proximately ntry value o owever, due r molecules, It has be uid. The res ction are qu nsors satur quilibrium p gure 9. P2 cated in the utting the slROCK
m triangular soil slope. T ng layer. A at the lower rface to inst ater can be rock. On th gh these con surface of Pore Press bedrock and e bedrock, action betweRUMENT
ater pressu Ts are used i positive an re installed e volume of quickly after aturated wit y 5.5 times of the porou e to the fact , the porous een demonst sults from t uite consist ated with t rocess for P and P3 are e upper par lope to mak r frame, wit The top surf A semi-circu r part of the all filter sto pumped thr he other han nnections in the bedrock sure Transd d the slope, o location of een the soil aTATION
ure measur in these ser nd negative in unsatur f water exch r pore press th a mixture that of the us stone, wh t that the inc s stone can r trated that t the negative tent with ththe two flu PPTs at diff e located at rt. The sligh ke the mod th an inclin face of this ular element e slope (Fig ones below, rough these nd, the rain n modelling k has 8 plac ducers (PPT or inside the f the sensor and rigid bed
AND MO
rements ries of tests e pore pres rated fine g hange. How sure change e of 50% G e water. The hich results creased visc remain satu the calibrati e pore pres e water rete uids measu ferent positi t the same ht increase del for the cnation of 38 bedrock is t is also con gure 1 and F from which e pipes into n water that g underlying ces to instal Ts). The s e soil mass. rs, and the drock.
ONITORI
to measure ssures. How grained mat wever, this f s and hence Glycerine an e higher vis s in a lowe cosity of the urated for a ion chart of ssure measu ention curv ured similar ions on the horizontal in suction centrifuge t 8°, is constr roughened nstructed to Figure 7). A h there are c the slope t t has infiltr g fractured b ll different ensors can . e Figure 8. water pipeING
the pore w wever, these terial becau feature mak e ideal for f nd 50% of w scosity of th er value for e fluid incre longer time f each senso urements wi ves of the R r values of interface be level in the at the end test. Subseq ructed to pr by gluing t model the A shallow n connections to simulate rated into th bedrock (Fi sensors, su be located The connect es beneath th ater pressur e sensors d use their flu kes them ve fast measure water. The v he saturatio the maxim eases the dr e (Muraleeth or is indepen ith PPTs sh Ruedlingen s f suction in etween soil e lower par of the equi quently, the rovide a rig the same so buttress eff notch is gro s to 4 water the exfiltra he soil mas igure 7). uch as Druc d either at ction of the s he bedrock.re. They are de-saturate luid reservo ery suitable ements. Acc viscosity of on fluid dec mum measu rag force on haran & Gra ndent from howed that soil. Moreo n the same and bedroc rt of the slo ilibrium cur e suction d gid underlyi oil to it as th ffect (Doglio oved latera pipes. On t ation of wat ss can also k PDCR81 the interfa sensors and t e calibrated quite quick oirs are sm for achievi cordingly, t f this blend creases the urable suctio n the diffusi anger, 1999 the saturati the values over, differe e model. T ck is shown ope and P6 rves is due ecreases aft ing hat oni lly the ter be or ace the to kly mall ing the d is air on. ing 9). ion of ent The in is to fter
spraying small amounts of water over the surface of the model. The comparison between the measurements using PPTs saturated with water and viscose blend shows that the time to reach equilibrium for the PPTs that are saturated with viscose fluid is slightly longer but the final values of suction agree quite well (Figure 10). These results are from the model preparation stage at 1g.
Figure 9. The time to reach equilibrium for the PPTs in unsaturated silty sand (w=15%, e=1.3).
Figure 10. Comparison between the PPTs saturated with different fluids.
7.2 Slope monitoring
Volumetric strains of the soil structure and movements of the slope are monitored by means of four 1.3 Megapixel IDS uEye UI-6240 C video cameras, which have been used in the full scale landslide triggering experiments in Ruedlingen (Akca et al., 2011). However, the lens of the cameras have been changed to cover the whole slope from the mean height of 300 mm, therefore wide angle SV_03514 lenses have been used. The lenses have been calibrated to reduce the distortion effect on the results. The specifications of the cameras and lenses are reported in Table 2. A series of reference points are attached to the walls of the climate chamber and the slope is illuminated by means of two white LED panels (Figure 11). The fixed reference points for the photogrammetry analysis are glued as sheets onto the walls of the boxes where they could be seen by all of the cameras. The cameras are fixed on the top plates of the climate chamber (Figure 12 and Figure 13).
A high speed camera is used to monitor the elevation of the slope during the tests (Figure 14). A recording code has been developed by which the pictures are taken in loops and only the last picture of each loop is saved unless a triggering mechanism is activated. This measure is taken due to the restrictions in the saving capacity of the computer and also it provides the opportunity to monitor both slow movements during the infiltration and fast slides during the failure.
Table 2. The specifications of the photogrammetry cameras and lenses. Specification Sensor type Sensor size Image resolution Frame rate Pixel pitch Lens focal length Lens view angle
CCD ½ inch 1280 x 1024 2 fps 4.65 microns 3.5 mm 76.6°x 103.6° (Diagonal:132.1°)
8
SUMMARY
Two landslide triggering experiments have been conducted on a natural slope in Northern Switzerland. The first experiment was not successful in terms of triggering a landslide, although higher average rain intensity for a longer period was applied to the slope. On the contrary, in the second experiment a landslide was triggered on the same slope but with different distribution of the rain concentration. A new climate chamber has been designed and constructed for a geotechnical drum centrifuge at ETHZ to investigate the stabilising factors in the first experiment and triggering mechanisms in the second one. Controlled conditions of rainfall intensity and duration together with temperature and relative humidity are provided in this chamber to study the hydrological and mechanical responses of the slope to different cycles of wetting and drying. A rigid slope underlying the soil is placed that enables the researcher to
-10 -5 0 0 50000 100000 150000 Pore w a ter pressuer (kPa) Time (s) P3-11392 P6-11189 P2-11391 -10 -5 0 0 50000 100000 150000 Pore w a ter pressue (kPa) Time (sec) P2-11395-viscose blend P2-11391-de aired water
stu vo pro ev Fig po Fig fro cra
AC
Th (C Re graudy the eff olumetric st ovide the ke
ents and/or
gure 11. Th ints and illum
gure 13. Pict om two para acking.
CKNOW
his research CCES) withi esearch Fun ateful to Mr fects of the trains, pore ey informat exfiltration e photogram mination sys tures from d allel tests shWLEDGEM
h was parti in the fram nd and EU r. Alfred Eh e drainage water pres tion to inves n from the u mmetry refer tem. different pho howing failuMENTS
ially funde mework of t project of hrbar for hisinto and ssure and th stigate the t underlying f rence Figur and l otogrammetry ure scarp an d by the C he TRAMM SafeLand s help in the exfiltration he rate of triggering m fractured be re 12. The s location of th y cameras nd tension Competence M – Projec (EU FP7 g e workshop. from the the movem mechanisms drock. schematic of he photogram Figure 14. a analysis, b) e Centre fo t. Other res grant agreem . bedrock. D ments of the of fast land
f the top plat mmetry came
a) The high s The side view
or Environm sources wer ment no. 22 Detailed ch e slopes ar dslides due tes of the cl eras. b) speed camer ew to the slop nment and re provided 26479). Th hanges in t e recorded to the rainf imate chamb a) ra used for P pe. Sustainabil d by the ET he authors a the to fall ber PIV ity TH are
REFERENCES
Akca, D., Gruen, A., Askarinejad, A. and Springman, S. M. (2011). Photogrammetric monitoring of an artificially generated landslide. Paper presented at the International Conference on Geo-information for Disaster Management (Gi4DM), Antalya, Turkey.
Askarinejad, A., Bischof, P., Beck, A., Casini, F. and Springman, S. M. (2012). Rainfall induced instabilities in a silty sand slope: a case history in northern Switzerland. submitted to RIG (Italian Geotechnical Journal).
Beck, A. (2011). Characterisation of a silty sand having a viscouse pore fluid. Master thesis, ETH. Brönnimann, C. (2011). Effects of Groundwater on Landslide Triggering. PhD thesis, EPFL.
Casini, F., Jommi, C. and Springman, S. M. (2010). A laboratory investigation on an undisturbed silty sand from a slope prone to landsliding. Granular Matter, 12 (3), 303-316.
Chu, J., Leroueil, S. and Leong, W. K. (2003). Unstable behaviour of sand and its implication for slope stability. Canadian Geotechnology Journal, 40, 873-885.
Doglioni, A., Galeandro, A. and Simeone, V. (2011), A simple model for passive failure compression structure at the toe of landslide. in The Second World Landslide Forum, eds. 98-113.
Eckersley, J. D. (1990). Instrumented laboratory flowslides. Géotechnique, 40, 489-502.
Harp, E. L., Wells, W. G. and Sarmiento, J. (1990). Pore pressure response during failure in soils. Geological Society of America Bulletin, 102, 428-438.
Hudacsek, P., Bransby, M. F., Hallett, P. D. and Bengough, A. G. (2009). Centrifuge modelling of climatic effects on clay embankments. Engineering Sustainability, 162 (ES2), 91-100.
Kimura, T., Takemura, J., Suemasa, N. and Hiro-Oka, A. (1991), Failure of fills due to rainfall. in Centrifuge 91, eds. H. Y. Ko & F. G. McLean, 509-516.
Ling, H., H.I., L., Li, L. and Kawabata, T. (2010), Centrifuge modeling of slope failures induced by rainfall. in 7th International Conference of Physical Modelling in Geotechnics, eds. S. M. Springman, J. Laue & L. Seward, 1131-1136.
Ling, H. I., Wu, M. H., Leshchinsky, D. and Leshchinsky, B. (2009). Centrifuge Modeling of Slope Instability. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 135 (6), 758-767.
Moriwaki, H., Inokuchi, T., Hattanji, T., Sassa, K., Ochiai, H. and Wang, G. (2004). Failure processes in a full-scale landslide experiment using a rainfall simulator. Landslides, 1, 277-288.
Muraleetharan, K. K. and Granger, K. K. (1999). The Use of Miniature Pore Pressure Transducers in Measuring Matric Suction in Unsaturated Soils. Geotechnical Testing Journal, 22 (3), 226-234. Ochiai, H., Okada, Y., Furuya, G., Okura, Y., Matsui, T., Sammori, T., Terajima, T. and Sassa, K.
(2004). A fluidized landslide on a natural slope by artificial rainfall. Landslides, 1, 211-220. Olson, S. M., Stark, T. D., Walton, W. H. and Castro, G. (2000). Static liquefaction flow failure of the
north dike of Wachusett dam. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 126 (12), 1184–1193.
Picarelli, L., Olivares, L. and Damiano, E. (2006). Discussion to “Evaluation of landslide triggering mechanisms in model fill slopes” by W.A. Take, M.D. Bolton, P.C.P. Wong, and F.J. Yeung, and “A fluidized landslide on a natural slope by artificial rainfall” by H. Ochiai, Y. Okada, G. Furuya, Y. Okura, T. Matsui, T. Sammori, T. Terajima, and K. Sassa ”. 3, 269–272.
Schofield, A. N. (1980). Cambridge Geotechnical Centrifuge Operations. Géotechnique, 30 (3), 227-268. Springman, S. M., Askarinejad, A., Kienzler, P., Casini, F., Sperl, M., Bleiker, E., Akca, D. and Gruen,
A. (2010). The Rüdlingen Monitoring and Landslide Experiment. D-Baug Highlights 2009, ETH Zürich, 26-31.
Springman, S. M., Laue, J., Boyle, R., White, J. and Zweidler, A. (2001). The ETH Zurich geotechnical drum centrifuge. International Journal of Physical Modelling in Geotechnics, 1 (1), 59-70.
Take, W. A., Bolton, M. D., Wong, P. C. P. and Yeung, F. J. (2004). Evaluation of landslide triggering mechanisms in model fill slopes. Landslides, 1, 173-184.
Tamate, S., Suemasa, N. and Katada, T. (2010), Simulating shallow failure in slopes due to heavy precipitation. in 7th International Conference of Physical Modelling in Geotechnics, eds. S. M. Springman, J. Laue & L. Seward, 1143-1149.
Taylor, R. N. (1995). Geotechnical centrifuge technology. Blackie Academic & Professional (Pub), Glasgow.
Wang, G. and Sassa, K. (2003). Pore-pressure generation and movement of rainfall-induced landslides: effects of grain size and fine-particle content. Engineering Geology 69, 109-125.
