scholarly journals Soil disturbance from pile driving in sensitive clay

1978 ◽  
Vol 15 (3) ◽  
pp. 346-361 ◽  
Author(s):  
M. Bozozuk ◽  
B. H. Fellenius ◽  
L. Samson
Keyword(s):  
Pore Water ◽  
Ground Surface ◽  
Soil Disturbance ◽  
Pile Driving ◽  
Horizontal Distance ◽  
Lateral Movement ◽  
Marine Clay ◽  
Eastern Canada ◽  
Overburden Pressure ◽  
Pore Water Pressures

Soil disturbance due to the driving of two groups of 116 concrete piles each in sensitive marine clay was studied on a construction project in eastern Canada. Pore-water pressures, heave, and lateral movement of soil and piles, and tests of strength, compressibility, and consistency limits of the soil were observed prior to and up to 3 months after pile driving whereas observations of pore-water pressures were continued for an additional 5 months. Driving of the piles had little effect on the compressibility and consistency limits of the marine clay, but the in situ shear strength and cone penetration resistance were reduced by about 15 and 30%, respectively. Soil heave within the group of piles decreased linearly with depth from a maximum of 450 mm (18 in.) at the ground surface to about zero at the pile tips, and in volume amounted to approximately 55% of the soil displaced by the piles. The vertical heave outside the pile group was confined to a horizontal distance of 12 m (39 pile diameters). During pile driving, the lateral movement of previously driven piles was as much as 175 mm (7 in.). Horizontal soil movements measured by inclinometers varied up to 125 mm (5 in.). Pore-water pressures generated during piling exceeded the total overburden pressure by 35–40%. The excess pore pressures dissipated in about 8 months after the piling was completed.

scholarly journals Subglacial Hydrology for an Ice Sheet Resting on a Deformable Aquifer

1986 ◽  
Vol 32 (110) ◽  
pp. 20-30 ◽  
Author(s):  
E. M. Shoemaker
Keyword(s):  
Pore Water ◽  
Coulomb Friction ◽  
Ice Sheet ◽  
Friction Angle ◽  
Water Channels ◽  
Water Drainage ◽  
Short Term ◽  
Overburden Pressure ◽  
Melt Water ◽  
Pore Water Pressures

AbstractSubglacial hydrology is investigated for an ice sheet where the substrate consists of a deformable aquifer resting on an aquitard. If sliding velocities are low or absent, subglacial melt-water drainage is dominated by drainage through the aquifer to water channels. Drainage along the bed is negligible. Efficient melt-water drainage requires that a system of subglacial water channels exists; otherwise, pore-water pressures will exceed the overburden pressure. In general, aquifer deformation near (away from) the terminus is most likely to occur during the winter (summer). The effect of short-term high channel pressures is, in general, not critical to aquifer deformation because the pressure pulse does not propagate far into the aquifer. (For aquifers of high permeability, short periods of high channel pressures constitute the most critical condition.) Aquifer deformation at the terminus is very likely to occur if the terminus ice slope exceeds tan ϕ, where ϕ is the Coulomb friction angle of the aquifer material. Upwelling of basal melt water near the terminus will normally cause soil dilation if the aquifer has a low permeability (e.g. till). Maximal profiles are computed corresponding to various aquifer materials using channel spacings which provide efficient drainage. (A maximal profile is the highest ice profile which the aquifer can sustain without deformation.) In general, maximal profiles lie well above observed profiles (such as h(x) = 3x1/2 (m)) except near the terminus. However, if channel spacings are sufficiently large, pore-water pressures are increased and maximal profiles can lie well below h(x) = 3x1/2.

Effects of freeze–thaw and softening on a natural clay at low stresses

1985 ◽  
Vol 22 (1) ◽  
pp. 69-78 ◽  
Author(s):  
J. Graham ◽  
V. C. S. Au
Keyword(s):  
Pore Water ◽  
Compacted Clay ◽  
Lake Agassiz ◽  
Overburden Pressure ◽  
Freeze Thaw ◽  
Weathering Processes ◽  
Preconsolidation Pressure ◽  
Pore Water Pressures ◽  
Access To Water

Weathering processes such as softening and freeze–thaw cycling affect the properties of clays. Care must therefore be taken when selecting strength and compressibility parameters for analysis of natural slopes, compacted clay embankments, and trench excavations in which significant proportions of the cross section can be affected by climatic weathering.Samples of plastic Lake Agassiz clay from Winnipeg were consolidated anisotropically in the laboratory to axial stresses less than or equal to the in situ effective overburden pressure. They were therefore all overconsolidated with respect to the field preconsolidation pressure. The samples were then loaded under drained or undrained conditions along steeply rising stress paths in p′, q stress space. One group of samples was tested immediately to identify the "undisturbed" behavior, a second group was subjected to freeze–thaw cycles, and a third group allowed to swell freely before testing.The freeze–thaw cycling produced increased compressibility and pore-water pressures, and reduced strengths at low stresses compared with the behavior of undisturbed clay. Freezing also caused the development of a clearly defined fissure structure. Softening at low stresses with access to water produced less marked effects. Key words: clay, undisturbed, freeze–thaw, softening, strength, yielding, pore-water pressures.

Effect of drainage and sequential filling on the behavior of backfill in mine stopes

2014 ◽  
Vol 51 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Nawfal El Mkadmi ◽  
Michel Aubertin ◽  
Li Li
Keyword(s):  
Pore Water ◽  
Numerical Study ◽  
Water Drainage ◽  
Filling Rate ◽  
Mining Operations ◽  
Overburden Pressure ◽  
Filling Sequence ◽  
Pore Water Pressures ◽  
Backfilled Stopes ◽  
Excess Pore

Underground backfilling offers significant economic and environmental advantages to mining operations. There is however a limited knowledge and understanding of how the backfill behaves within mine stopes, which creates some concern regarding the risk of accidents with potentially serious consequences. It is thus important to investigate further the response of backfill to ensure safe working conditions and optimize the filling sequence. This paper presents key results from a numerical study aimed at analyzing the hydrogeotechnical response of backfill in a narrow vertical stope. The simulations illustrate how stresses are influenced by stope geometry, water drainage, and filling rate. Three main cases are presented here to illustrate these effects; namely, (i) simulation of dry (or drained) backfill, (ii) a rapidly filled stope with progressive drainage and consolidation, and (iii) sequential backfill placement with different filling rates. The third case includes a simulation with evolving properties due to the binder added to the backfill. The results from the numerical analyses show that arching effects develop within narrow backfilled stopes because of the stiffness contrast between the rock and the fill material. This can produce a significant reduction of the stresses (horizontal and vertical) in comparison with the overburden pressure. The simulation results also show the development of excess pore-water pressures after the placement of the saturated backfill within the stope. Drainage tends to reduce these pressures and increase the frictional stresses along the rock walls. The sequentially filled stope simulations show that a rapid filling rate produces much higher total stresses and excess pore-water pressures, compared to slower rates. The simulation of the cemented backfill, with evolving properties, indicates that the progressive changes can have a significant effect on the total and effective stresses in the stope. A discussion follows on the implications of these results.

scholarly journals A Numerical Investigation of the Deformation Mechanism of a Large Metro Station Foundation Pit under the Influence of Hydromechanical Processes

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Yan Wang ◽  
Yongjun Zhang ◽  
Mingfei Li ◽  
Yi Qi ◽  
Tianhui Ma
Keyword(s):  
Pore Water ◽  
Heavy Rainfall ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Ground Surface ◽  
Horizontal Displacement ◽  
Horizontal Distance ◽  
Foundation Pit ◽  
Metro Station ◽  
Ground Conditions

Considering the unique conditions of deep and large subway foundation pit excavation affected by heavy rainfall in soil-rock composite strata, this paper employs finite element numerical simulation methods to study foundation pit instability under the influence of heavy rainfall. According to the hydraulic coupling conditions caused by rainfall, a fluid-solid coupling numerical model for a deep and large subway foundation pit in soil-rock composite strata is established in this paper. By selecting the Anshan road station of Qingdao subway line 4 as the engineering background, various parameters related to foundation pit excavation affected by heavy rainfall at different excavation depths were analyzed. The study found that after the foundation pit was excavated, the surrounding pore water pressure decreased and the pore water pressure near the ground surface increased rapidly due to rainfall. As the horizontal distance from the foundation pit increased, the pore water pressure at the same depth also increased. The excavation of the foundation pit caused uplift of the bottom of the pit. After rainfall, the uplift value decreased compared with that before rainfall. With increasing excavation depth, the decreased value of the bottom uplift decreased and then increased. The rainfall caused the horizontal displacement of the pit walls on both sides of the pit to increase. When the excavation depth was 10 m, the horizontal displacements on both sides of the pit were equivalent. When the excavation depth was 20 m, the horizontal displacement was concentrated in the first 10 m; when the excavation depths were 30 m and 40 m, the horizontal displacement was concentrated in the first 13 m. This finding shows that when the foundation pit was affected by rainfall, the sidewall collapsed at a distance of 13 meters from the ground. As the excavation depth increased, the depth of excavation instability was closer to the bottom of the pit. The research in this paper can provide a reference for the construction of deep and large foundation pits in similar composite ground conditions that are affected by rainfall.

Three-dimensional numerical investigations of groundwater responses in an unsaturated slope subjected to various rainfall patterns

2001 ◽  
Vol 38 (5) ◽  
pp. 1049-1062 ◽  
Author(s):  
C WW Ng ◽  
B Wang ◽  
Y K Tung
Keyword(s):  
Pore Water ◽  
Short Duration ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Three Dimensional ◽  
Ground Surface ◽  
Rainfall Pattern ◽  
Initial Water ◽  
Pore Water Pressures ◽  
Rainfall Patterns

Three-dimensional (3D) numerical analyses were conducted to investigate groundwater responses in an initially unsaturated cut slope at Lai Ping Road in Hong Kong subjected to rainfalls with various patterns, durations, and return periods. Initial and boundary conditions were established from field monitoring data. The computed results show that rainfall pattern has a significant influence on pore-water pressures in soil layers near the ground surface but its influence gradually diminishes with depth. Rainfall with an advanced storm pattern of 24 h duration was found to be the most critical because it results in the highest pore-water pressure in the slope. At a given depth, the influence of rainfall pattern on pore-water pressures depends on the initial groundwater conditions: the higher the initial water table, the smaller the influence of rainfall pattern on pore-water pressures. Under a given rainfall duration, the rise of pore-water pressure at the study site is significant only when the return period increases from 10 years to 100 years, but not from 100 years to 1000 years. Short-duration, intense rainfall causes larger variations in pore-water pressure at shallow depths, whereas long-duration rainfall has a greater influence on groundwater in deep soils because of the generally greater amount of rainfall. For prolonged rainfalls, the difference in pore-water pressure distribution resulting from different rainfall patterns is less significant than that from short-duration, intense rainfalls.Key words: Lai Ping Road, rainfall patterns, pore-water pressure distributions, suction, unsaturated slope.

The Effects of Seismic Pore Water Pressure on Ground Surface Motion

1994 ◽  
Vol 10 (2) ◽  
pp. 403-438 ◽  
Author(s):  
George(Bebe)T. Zorapapel ◽  
Mladen Vucetic
Keyword(s):  
Pore Water ◽  
Fourier Transforms ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Ground Surface ◽  
Surface Motion ◽  
Surface Displacements ◽  
Acceleration Time Histories ◽  
Pore Water Pressures ◽  
Time Histories

The effects of the gradual buildup of seismic pore water pressures and associated degradation of stiffness on the ground surface motion are examined for shallow saturated liquefiable deposits. Ground surface displacements and accelerations, the Fourier Transforms of the acceleration-time histories and layer gain factors are analyzed. The analysis is based on the ground surface and sub-surface accelerations and pore water pressures recorded at sites that either fully liquefied or built up considerable pore water pressures during strong earthquakes. The analysis shows that: (i) the seismic pore water pressures within the deposit and the ground surface motion are intimately related, (ii) relatively small seismic excess pore water pressures can cause a considerable lengthening of the predominant period of the ground surface motion, and (iii) these phenomena may lead to a limited maximum ground surface acceleration of approximately 0.2g, and a considerable increase of maximum ground displacements.

scholarly journals Subglacial Hydrology for an Ice Sheet Resting on a Deformable Aquifer

1986 ◽  
Vol 32 (110) ◽  
pp. 20-30 ◽  
Author(s):  
E. M. Shoemaker
Keyword(s):  
Pore Water ◽  
Coulomb Friction ◽  
Ice Sheet ◽  
Friction Angle ◽  
Water Channels ◽  
Water Drainage ◽  
Short Term ◽  
Overburden Pressure ◽  
Melt Water ◽  
Pore Water Pressures

AbstractSubglacial hydrology is investigated for an ice sheet where the substrate consists of a deformable aquifer resting on an aquitard. If sliding velocities are low or absent, subglacial melt-water drainage is dominated by drainage through the aquifer to water channels. Drainage along the bed is negligible. Efficient melt-water drainage requires that a system of subglacial water channels exists; otherwise, pore-water pressures will exceed the overburden pressure. In general, aquifer deformation near (away from) the terminus is most likely to occur during the winter (summer). The effect of short-term high channel pressures is, in general, not critical to aquifer deformation because the pressure pulse does not propagate far into the aquifer. (For aquifers of high permeability, short periods of high channel pressures constitute the most critical condition.) Aquifer deformation at the terminus is very likely to occur if the terminus ice slope exceeds tanϕ, whereϕis the Coulomb friction angle of the aquifer material. Upwelling of basal melt water near the terminus will normally cause soil dilation if the aquifer has a low permeability (e.g. till). Maximal profiles are computed corresponding to various aquifer materials using channel spacings which provide efficient drainage. (A maximal profile is the highest ice profile which the aquifer can sustain without deformation.) In general, maximal profiles lie well above observed profiles (such ash(x) = 3x1/2(m)) except near the terminus. However, if channel spacings are sufficiently large, pore-water pressures are increased and maximal profiles can lie well belowh(x) = 3x1/2.

Pore-Water Pressures Induced by Pile Driving

1979 ◽  
Vol 105 (11) ◽  
pp. 1349-1354
Author(s):  
Nabil F. Ismael ◽  
Tony W. Klym
Keyword(s):  
Pore Water ◽  
Pile Driving ◽  
Pore Water Pressures

Regional geology and landslides in the marine clay deposits of eastern Canada

1970 ◽  
Vol 7 (2) ◽  
pp. 145-156 ◽  
Author(s):  
P. La Rochelle ◽  
J. Y. Chagnon ◽  
G. Lefebvre
Keyword(s):  
Shear Strength ◽  
Pore Water ◽  
Flow Conditions ◽  
Marine Clay ◽  
Eastern Canada ◽  
Regional Geology ◽  
Clay Deposits

A detailed inventory of the numerous landslides which have taken place in the Province of Quebec has shown that they are concentrated in given areas. Extensive studies carried out in three different areas have revealed a coincidence between the concentration of landslides and the existence of valleys in the bedrock underlying the clay deposits.Piezometric levels measured on the field have consistently shown the prevalence of a downward gradient in the upper part of the slope and an upward gradient with artesian pressure at the toe. These flow conditions which can be imputed in part to the presence of the valley in the bedrock produce the leaching of the salt in the pore water of the clay resulting in a decrease of the shear strength and an increase of sensitivity of the clay.

Sign in / Sign up

Export Citation Format

Share Document