Creep Movement Research Articles

Modelling consolidation accelerated by vertical drains in soils subject to creep

The settlement of embankments and reclamations over soft soils is frequently accelerated by the use of vertical drains. The magnitude of long-term settlement is sometimes reduced by the use of surcharge, although there is often uncertainty about how long the surcharge should be maintained to minimise creep movement. The design of vertical drains is generally based on closed-form solutions of Terzaghi's consolidation equation, and rarely takes into account non-linear stiffness and creep of the soil. In this paper a one-dimensional finite difference consolidation analysis is outlined showing how vertical and radial drainage of a multi-layer soil profile in the zone of influence of a vertical drain may be modelled. The analysis allows inclusion of a zone of peripheral smear around the drain and drain resistance, permeabilities may be varied with void ratio, and creep is modelled both during and after primary consolidation. The application of the model is illustrated with back-analysis of field data from construction of an embankment with temporary surcharge over estuarine alluvium.

Micro-sheeting of granite and its relationship with landsliding specifically after the heavy rainstorm in June 1999, Hiroshima Prefecture, Japan

Certain types of granite in mountainous areas are microscopically sheeted to a depth of 50 m due to unloading under the stress field that reflects slope morphology. Micro-sheets generally strike parallel to major slope surfaces and gently dip downslope, forming cataclinal overdip slopes. The cataclinal overdip slope accelerates creep movement of micro-sheeted granite, which in turn loosens and disintegrates granite via the widening or neoformation of cracks, probably in combination with stress release, temperature change, and changes in water content near the ground surface. The surface portion of micro-sheeted granite is thus loosened with a well-defined basal front, which finally slides in response to heavy rain. Innumerable landslides of this type occurred in Hiroshima Prefecture, western Japan, following the heavy rainstorm of 29 June 1999. Following such landslides, the weathering of micro-sheeted granite exposed on the landslide scar recommences, setting the stage for future landslide.

Continuous monitoring of an active fault in a plate suture zone: a creepmeter study of the Chihshang Fault, eastern Taiwan

Data from continuously monitored creepmeters across the active Chihshang Fault in eastern Taiwan are presented. The Chihshang Fault is an active segment of the Longitudinal Valley Fault, the main suture between the converging Philippine and Eurasian plates in Taiwan. Since the 1951 earthquake (Mw=7.0), no earthquake larger than magnitude 6.0 occurred in the Chihshang area. At least during the last 20 years, the Chihshang Fault underwent a steady creep movement, resulting in numerous fractures at the surface. Five creepmeters were installed in 1998 at two sites, Tapo and Chinyuan, within the Chihshang active fault zone. One-year results (from August 1998 to July 1999) show a horizontal shortening of 19.4±0.3mm and 17.3±0.7mm, at Tapo and Chinyuan, respectively. These annual shortening rates are in a good agreement with other estimates of strain rate independently obtained from geodetic measurements and geological site investigation. The creepmeter measurements were made on a daily basis, providing accurate information on the previously unknown evolution of creep during the year. The records of fault creep at the Tapo site thus revealed close seasonal correlation with average rainfall: the period of high creep rate coincides with the wet season, whereas that of low creep rate coincides with the dry season. Also, in comparison with the Tapo site, the creep behaviour as a function of time is complex at the Chinyuan site. Possible factors of irregularity are under investigation (thermal effect acting on the concrete basement of the creepmeters, earth tide effect, water table variations in a nearby rice field, and rainfall). The comparison between GPS measurements across the Longitudinal Valley (31mm/year of horizontal displacement) and the creepmeter measurement across the Chihshang Fault zone (17–19mm/year of horizontal displacement) suggests that there exists other shortening deformation across the active fault zone in addition to those we have measured from the creepmeters.

Modelling consolidation accelerated by vertical drains in soils subject to creep

The settlement of embankments and reclamations over soft soils is frequently accelerated by the use of vertical drains. The magnitude of long-term settlement is sometimes reduced by the use of surcharge, although there is often uncertainty about how long the surcharge should be maintained to minimise creep movement. The design of vertical drains is generally based on closed-form solutions of Terzaghi's consolidation equation, and rarely takes into account non-linear stiffness and creep of the soil. In this paper a one-dimensional finite difference consolidation analysis is outlined showing how vertical and radial drainage of a multi-layer soil profile in the zone of influence of a vertical drain may be modelled. The analysis allows inclusion of a zone of peripheral smear around the drain and drain resistance, permeabilities may be varied with void ratio, and creep is modelled both during and after primary consolidation. The application of the model is illustrated with back-analysis of field data from cons...

A Risk Evaluation of Landslides in Use of Critical Surface Displacement

This paper deals with the index for risk evaluation of landslides, focusing on surface displacement at main scarp to collapse. Rainfall experiments indicate the existence of critical cumulative displacement at which a slope starts to collapse rapidly after the creep movement. A statistical analysis of various field and experimental data show that the critical cumulative displacement is in proportion with the length of the source area, and the ratio of critical cumulative displacement to the length of the source area (critical strain) ranges approximately from 0.006 to 0.02. Then an index of four-stage evaluation on the basis of the above range is proposed: precursor stage (<0.003), warning stage (0.003-0.006), failure stage (0006-0.02), and perfect failure stage (>0.02). Finally the wide validity of the proposal is verified by applying to several active landslides and old landslides.

An effective diffusion barrier metallization process on copper

Copper substrates have been widely used to mount semiconductor device chips due to their high electrical and thermal conductivity. To achieve high heat conduction, solders are utilized to bond the chip on the substrate. Soft and ductile solders such as indium and lead–tin alloys are often used to help release the stress developed in a bonded structure through plastic deformation and strain. In the solder joint, a major concern is the formation of intermetallics caused by the diffusion of copper atoms from the substrate to the joint. The growth of intermetallics makes the solder joint less ductile and less capable of releasing stresses. Prevention of copper diffusion is needed in applications where the solder joint must remain soft and ductile. On the other hand, in applications where creep movement cannot be tolerated, hard solders such as AuSn eutectic alloy should be considered. In this paper, we report a barrier metallization technique on copper substrates to block copper atoms from diffusing into the solder. Indium was selected as the solder medium in this study because of its increasing applications in many photonic devices such as laser diodes and photonic switches. Other solders such as lead–tin alloys can be also used with the metallization process. The metallization consists of Ni buffer layer and Cr blocking layer. The solder joint is fabricated by the fluxless bonding technology. After accelerated aging test at 130°C for 100 h, no sign of copper diffusion through the metallization is detected using energy dispersive X-ray (EDX). If 90°C is the maximum temperature of the solder joint during device operation, the corresponding time for no copper diffusion is 107 500 h, or 12.3 years. This result shows that the metallization process developed in this research is, indeed, very effective.

The effect of unit water absorption on long-term movements of masonry

Long-term movements in masonry can be predicted by composite modelling, however, the accuracy of prediction is reduced if the unbonded brick and mortar phases do not reflect the behaviour of the bonded components. It is apparent that the water absorbed by the unit soon after laying produces changes in the behaviour of the bonded components of the masonry especially of the mortar joints, which have reduced creep and shrinkage. This paper presents a study of the transfer of moisture between the brick and mortar components from 30 min after laying of bricks to 120 days. Subsequently, unit water absorption modification factors are developed which improved the accuracy of predicting creep and moisture movement strain of masonry by composite models to within 10% of the measured values.

Mechanism of creep movement caused by landslide activity and underground erosion in crystalline schist, Shikoku Island, southwestern Japan

The mechanism of creep movement of the Zentoku landslide in crystalline schist has not been studied in detail because of the steepness of the slope, very slow movement, low population density and complex topographic and geologic characteristics. Sassa et al. (1980: Proc. INTERPRAEVENT 1, 85–106) and Sassa (1984: Proc. 4th International Symp. on Landslides, Toronto, vol. 2, pp. 179–184; 1985. Geotechnical classification of landslides, Proc. 4th International Conference and Field Workshop on Landslides, Tokyo, pp. 31–40; 1989: Landslide News, Japan Landslide Society, No. 3, pp. 21–24) monitored landslide movement and groundwater level at the Zentoku landslide on Shikoku Island, southwestern Japan, and suggested that the mechanism may be caused by underground erosion. To study the influence of underground erosion at this site, continual monitoring of suspended sediment and water discharge from a groundwater outlet (i.e. a spring) was implemented. The locations of groundwater flow paths were determined, as were the amounts of discharged sediment. Slope deformation was monitored by means of a borehole inclinometer. The conclusions were as follows: (1) the flow paths were found to be on or above the shear zones in which underground erosion has occurred; (2) in addition to being a result of precipitation and groundwater discharge, sediment discharge is affected by landslide activity; and (3) the mechanism of creep movement is an interrelated chain process that combines underground erosion caused by landslide activity with landslide activity caused by underground erosion. Thus, landslide activity increases erosion susceptibility and transportation of soils within the mass, and underground erosion causes instability of the landslide mass, in turn. This mechanism can explain the observed phenomenon that the Zentoku landslide not only moves actively during heavy rain, but also continues to creep throughout the year.

Effect of incremental loading on the creep behaviour of chemically grouted sand

This paper describes the results of a study on the stress-strain time dependent (creep) behaviour of silicate-Hardener 600B grouted Leighton Buzzard sand specimens when subjected to incremental loading at certain time intervals. Unconfined and confined multi-stage creep tests were conducted on sand specimens injected with different silicate content grouts which cover the range generally used in engineering practice. The laboratory results showed that creep movements increase with the increase in stress ratio causing a rise in strain rate which ultimately leads to creep rupture (complete failure). However, an increase in the stress ratio does not affect the linear relationship between logarithm of strain rate and the logarithm of time suggesting that the three parameter phenomenological relationship of Singh and Mitchell (1968) may be suitable to describe the multi-stage creep behaviour of silicate-Hardener 600B grouted sand.

Microdeformation of lacustrine laminite sequences from Late Miocene formations of SE Spain: an interpretation of loop bedding

Lacustrine laminated sediments (laminites) present in Late Miocene formations of the Híjar Basin, SE Spain, display well developed loop bedding, a structure consisting of bundles of laminae that are sharply constricted at intervals, giving a morphology of loops or links of a chain. The laminite sequences, which are interbedded with turbidite marlstones, were accumulated on the bottom of a permanently stratified lake developed in a rapidly subsiding basin limited by 010° and 105° normal faults. As deduced from both macro‐ and microdeformational analyses, the basin evolved under an extensional stress field throughout the Late Miocene. Four main types of loops, simple and complex loops with subcategories, have been recognized within the laminite sequence. Simple loops of type 1 show the best definite pattern, quite similar to ‘pinch and swell structures’, a type of boudinage typical of stretching of alternating beds where the competence contrast is not strongly marked. The remaining loop types display contortion and occasional breakage of laminae (microfaulted edges) indicative of microdeformation near the boundary between the ductile‐brittle deformational fields. The distribution of the various loop types across the laminite sequence reflects an interplay between progressive lithification of the laminites as sedimentation progressed and tectonic stresses which affected the sediment sequence. Accordingly, a mechanism of deformation under an extensional stress field, ultimately related to the creep movement of the main basin faults which resulted in successive seismic shocks of low magnitude, is proposed to explain the formation of loop bedding in the laminites.

Should Grouted Anchors Have Short Tendon Bond Length?

Field measurements associated with the behavior of ten low-pressure grouted anchors installed with a hollow stem auger at the National Geotechnical Experimentation Site at Texas A&M University are presented. The anchors were 0.3 m in diameter and embedded 13.8 m in a stiff to very stiff clay. Six anchors had a tendon bond length of 4.6 m and four had a tendon bond length of 9.2 m. All anchors were load tested to near failure, some were subjected to creep tests, and some to long-term relaxation tests. This study evaluates the load distribution in the soil, grout, and steel tendon; the shear strength of the soil-grout interface compared to engineering soil properties; the relationships between the ultimate load, the creep failure load, the creep threshold load, and the design load; the creep movement rate under load; and the load loss as a function of time. The results show that anchors with shorter tendon bond lengths have higher ultimate capacities and lower creep rates, and transfer the load further away from the supported structure.

The movement mechanism of crystalline-schist landslide associated with underground erosion

It has been estimated that creep movement is caused by underground erosion in the crystalline-schist debrismass landslide. However, it is not sufficient to explain the movement mechanism of landslide.Then, the authors carried out monitoring of sediment discharge caused by underground erosion, landslide mass deformation and measurement of underground water paths in Zentoku landslide mass, Tokushima prefec-ture, Japan, to clarify the movement mechanism of such type of landslide. From the results of analysis about the factor affected to underground erosion using these monitoring and measurement results, it is considered that (1) water paths are formed along/above the shear zones, where underground erosion is caused (2) sediment discharge caused by under ground erosion is affected by the factors of not only groundwater discharge but also landslide activity (3) high landslide activity makes the debris mass structure subjected to underground erosion in the landslide mass. Consequently, the investigation has made clear that the mechanism of creep movement consists of the link of two processes, one is underground erosion caused by landslide activity, and another islandslide activity caused by underground erosion.

Analysis of Snake Movement Forms. 2nd Report. Comparison of the locomotive efficiencies for various movement forms of snake creep locomotion.

In this work, we compared the locomotive efficiencies for various creep movement curves of snake locomotion, by analyzing the power density function and the ratio of the tangential force to the mormal force. The results show that the proposed Serpentine curve (S. Ma, JSME Trans., Vol. # 62, No. # 593 (C), pp. # 230-236, 1996) is more valid as the snake creeping locomotion shape than the Clothoid and Serpenoid curves (S. Hirose, Biologically Inspired Robots, Oxford University Press, 1993).

Plasma sprayed copper-nickel-indium coatings on titanium alloys: A. Koutsomichalis, H. Badekas (National Technical University of Athens, Athens, Greece). Mater. and Manuf. Processes, vol 10, no 5, 1995, 1087–1092

Copper substrates have been widely used to mount semiconductor device chips due to their high electrical and thermal conductivity. To achieve high heat conduction, solders are utilized to bond the chip on the substrate. Soft and ductile solders such as indium and lead–tin alloys are often used to help release the stress developed in a bonded structure through plastic deformation and strain. In the solder joint, a major concern is the formation of intermetallics caused by the diffusion of copper atoms from the substrate to the joint. The growth of intermetallics makes the solder joint less ductile and less capable of releasing stresses. Prevention of copper diffusion is needed in applications where the solder joint must remain soft and ductile. On the other hand, in applications where creep movement cannot be tolerated, hard solders such as AuSn eutectic alloy should be considered. In this paper, we report a barrier metallization technique on copper substrates to block copper atoms from diffusing into the solder. Indium was selected as the solder medium in this study because of its increasing applications in many photonic devices such as laser diodes and photonic switches. Other solders such as lead–tin alloys can be also used with the metallization process. The metallization consists of Ni buffer layer and Cr blocking layer. The solder joint is fabricated by the fluxless bonding technology. After accelerated aging test at 130°C for 100 h, no sign of copper diffusion through the metallization is detected using energy dispersive X-ray (EDX). If 90°C is the maximum temperature of the solder joint during device operation, the corresponding time for no copper diffusion is 107 500 h, or 12.3 years. This result shows that the metallization process developed in this research is, indeed, very effective.

SOIL CREEP DYNAMICS, SOIL MOISTURE AND TEMPERATURE CONDITIONS ON A FORESTED SLOPE IN THE GRANITIC VOSGES MOUNTAINS, FRANCE

Soil creep, soil water tension and soil temperature were monitored at the Schildmatt experimental site over a 7 month period, in order to study the dynamics of creep movements measured with a specially designed strain gauge probe. The limited displacements and the very low signals which had to be measured were taken into account in estimating the uncertainty in measurements. The results obtained emphasize the very discontinuous and highly reversible character of the creep movements and their seasonal nature. Displacements occurred mainly during two events: their size were 10 mm and 2 mm, but the overall displacements for the whole intensive study period (January–July 1985) was only 3 mm. The relationships with soil moisture and temperature conditions indicated that ice segregation and saturated conditions are major influences, but more needs to be known about the way they act on soil creep.

SOIL CREEP DYNAMICS, SOIL MOISTURE AND TEMPERATURE CONDITIONS ON A FORESTED SLOPE IN THE GRANITIC VOSGES MOUNTAINS, FRANCE

Soil creep, soil water tension and soil temperature were monitored at the Schildmatt experimental site over a 7 month period, in order to study the dynamics of creep movements measured with a specially designed strain gauge probe. The limited displacements and the very low signals which had to be measured were taken into account in estimating the uncertainty in measurements. The results obtained emphasize the very discontinuous and highly reversible character of the creep movements and their seasonal nature. Displacements occurred mainly during two events: their size were 10 mm and 2 mm, but the overall displacements for the whole intensive study period (January–July 1985) was only 3 mm. The relationships with soil moisture and temperature conditions indicated that ice segregation and saturated conditions are major influences, but more needs to be known about the way they act on soil creep.

Numerical modelling of crustal stresses in the eastern Australian passive margin∗

In the Australian continent, particularly in eastern Australia, the intraplate stresses and the absolute plate velocity trajectory are not aligned. This is in contrast to some lithospheric plates (e.g. North America), for which the intraplate crustal stress appears to be related to the plate boundary driving forces. In an attempt to understand this unique stress pattern, a computer model has been constructed for part of the eastern Australian passive margin. The model adopts the regional tectonic‐geometric configuration (an east‐west cross‐section 700 km long and 150 km deep) and the material properties for the relevant rocks as input. Different tectonic situations are simulated using variable boundary conditions. The modelling results show that gravity‐induced body forces cause the materials in the various layers of the section to creep towards the continent. This process alone is sufficient to create horizontal compression of sufficient magnitude in eastern Australia to account for the observed crustal seismicity. The upper plate passive‐margin geometry of eastern Australia and the involvement of an upper mantle wedge are decisive in the creation of gravitational creep movement towards the continent in the lithosphere, and any east‐west remnant or plate boundary stress further enhances the horizontal compression. The gravitational creep movement also gives rise to uplift in the shallow crust. The location of the predicted uplift is consistent with geological observation. Furthermore, brittle yielding has been observed at certain locations in the modelled section, roughly confined to a 190 km wide zone across the coastline, consistent with present day seismic observations. The present day intraplate stress system in eastern Australia appears to result from a combination of that due to the upper plate passive margin geometry (resulting in roughly east‐west compression or normal to the continental‐oceanic crustal boundary) and that due to plate motion (resulting in approximately north‐south compression). The resultant stress distribution is therefore highly variable with east‐west compression more commonly dominant than north‐south compression.

Analysis of Snake Movement Forms. 1st Report. Standard Creep Movement Forms of Snake.

In this paper, we elucidate the standard creep movement forms (S-shaped curve) of a snake, which is the typical locomotive movement shown by snakes. Serpentine curve in the constant steady state velocity and ex-serpentine curve in the constant steady state acceleration are derived for the uniform creep locomotion of the snake, through analyzing physiologically its muscle characteristics, Muscular force is also discussed for these two types uniform locomotive curves. The results proposed here are demonstrated by computer simulation to agree with previously reported experimental results (Y. Umetani and S. Hirose, Trans. of the Society of Instrument and Control Engineers, 10-5 1974, 513-518, in Japanese).

Geohistorical development of the Tochiyama landslide in north-central Japan

The Tochiyama landslide is one of several complex, deep-seated and large-scale landslides occurring in the Hokuriku Province in central Japan. The landslide is about 2 km long and about 500–1100 m wide; it occupies an area of approximately 150 ha and has a maximum depth of 60 m. The slide developed on a dip-slope structure, and is divisible into three layers in ascending order: older landslide debris and avalanche deposits, younger debris-avalanche deposits, and talus. The landslide complex is still active. A triangulation point on the upper part of the landslide shifted downhill by 3.3 m from 1907 to 1983, indicating an average rate of 4.3 cm/y. In 1991, the average rate of movement on the sliding surface was also 4.3 cm/y as measured by an automatic system with inclinometers installed in borehole No. 1–2. The rate measured for borehole No. 1–3, located 380 m upslope from No. 1–2, was over twice that of No. 1–2 for the same period; it has since accelerated to about 19 cm/y. Thus current movements on the basal sliding surface are inhomogeneous; the head of the slide complex is increasing the horizontal granular pressures on the lower part of the slide block. On the basis of dating of two tephra layers and 14C dating of carbonized wood intercalated within the landslide body, two stages of slide movement have been distinguished. The earlier occurred between about 46,000 to 25,000 years ago, and the latter occurred since 1361 A.D. The following sequence of events is inferred. During the middle Pleistocene, intense tectonic movements occurred in the Hokuriku Province, and as a consequence dip-slopes were developed in the Tochiyama landslide area. Low-angle fault planes (possibly representing slump features) and fracture zones then developed within flysch deposits underlying the landslide area, causing a reduction in shear strength. The erosion base level was lowered during the Würm glacial age, and due to severe erosion and incision of stream valleys, the surface slope angle rapidly increased, and toe resistance decreased. This combination of causes led to the development of a deep-seated primary landslide. As a result of an accumulation of younger deposits, regional uplift and further local erosion, stability of parts of the region decreased and led to landslide activity of a second stage. Reactivated and locally accelerating creep movements occur today and may forewarn of a stage of reactivated, hazardous rapid sliding, such as occurred with the adjacent and analogous Maseguchi landslide in 1947.

Effect of rock masses surrounding concrete dams on their behavior

1. Geodynamic movements of surrounding rock masses can affect the behavior of arch dams. Creep movements of slopes can cause a change in the former scheme of static behavior of a dam, being expressed in a different reaction to the previous combination of acting loads. 2. The effect of seismotectonic activity during the earthquake precursory period is manifested in the form of fluctuations of the on-site data: strain-gauge, geodetic, and piezometric. The location of the detector that recorded fluctuations and values of these fluctuations characterize the temporal change in the scheme of static behavior of the dam reacting to deformation of the blocks and slabs of the surrounding masses. 3. For concrete dams constructed in narrow mountain canyons, it is necessary to conduct on-site observations according to a special program compiled on the basis of an analysis of the state of the dam in the first years of operation to detect geodynamic and seismotectonic activity. These observations should be informative for: Determination of the effect of the surrounding rock masses on the state of the dam; study of the role of technogenic factors in natural processes; selection of earthquake precursors; determination of the seismic stability of the dam. 4. On all dams constructed in mountain canyons it is necessary to make a retrospective analysis of the on-site data to determine the interrelations in the reservoir-dam-surrounding rock mass system. 5. The data of on-site observations of the responses of a dam to geodynamic and seismotectonic processes can be used by basic science for gaining knowledge about the earth's crust.