Review of Causes of Foundation Failures and Their Possible Preventive and Remedial Measures by Dr. Amit Srivastava (1)

1
Review of Causes of Foundation Failures and Their
Possible Preventive and Remedial
MeasuresbyDr. Amit SrivastavaAssociate
Professor, Department of Civil Environmental
EngineeringThe NorthCap University, HUDA Sector
23-A Gurgaon - 122017.
2
Contents

• Introduction
• Load transfer failures
• Drag down and heave
• Collapsible soils
• Lateral loads
• Construction error
• Unequal support

3
Contents
Contents

1. Water level fluctuation
2. Earthquake
3. Vibration effect
4. Foundation failure due to landslide/ slope
   instability
5. Foundation failure due to uplift
6. Conclusion

4
Introduction

• Foundations of engineering constructions are
  systems that act like interface elements to
  transmit the loads from superstructure to, and
  into, the underlying soil or rock over a wider
  area at reduced pressure.  
• Engineering structures despite being constructed
  with adequate strength and safety measures do
  fail or collapse.
• Failure is an unacceptable difference between
  expected and observed performance. Council of
  Forensic Engineering, ASCE

5
Load transfer failures

• The objective of foundation is to transfer the
  load of superstructure to the foundation soil on
  a wider area.
• The uncertainties for which factor of safety is
  provided in geotechnical design include (a) the
  natural heterogeneity or inherent variability (b)
  measurement error, and (c) model transformation
  uncertainty.
• Classic examples of Bearing capacity failures
  Transcona Grain elevator in 1913 and Fargo Grain
  Elevator in 1955.

6
Transcona elevator
Figure 1. East side of Transcona elevator
following foundation failure
7
Preventive measures and remedies

• Under such circumstances, the most commonly
  adopted remedial measure to rectify the problem
  is underpinning.
• Underpinning is accomplished by extending the
  foundation in depth or width so that it either
  rests on a more supportive soil stratum or
  distributes its load across a greater area.
• Use of steel piers, helical anchors and micro
  piles are common methods in underpinning.

8

• Figure 2. Foundation Underpinning by hydraulic
  jacking and transfers loads to screw foundations
  installed into stable strata

9
Drag down and heave

• In plastic soils, new settlements (drag down) are
  often accompanied by upward movements and heave
  some distance away.
• In swelling and shrinking soils, hot dry wind and
  intense heat will often cause the soil to shrink
  beneath the foundation.
• Uneven saturation of the soil around foundation
  (located in expansive soils) can cause the soil
  to heave as it expands and contracts after
  drying.
• Similar problem of heave and contraction is
  observed when foundation is placed in extremely
  cold condition (below freezing point).

10
Types of settlement
Figure 3. Pictorial representation of structural
damage caused by drag down and heave
11
Damages due to expansive soils
12
Preventive measures and remedies

1. Soil stabilization with lime, lime-fly ash,
   Portland cement, etc.
2. Control of soil moisture using plastic fabric
   underneath the foundation,
3. A thin coat of bitumen will drastically reduce
   the shear-force between the pile surface and the
   soil and reduce the negative skin friction,
4. Ignoring active zone of expansion and contraction
   by placing footing at deeper depth or providing
   pile/ belled piers,
5. Heavy structure to overcome swell pressure,
6. Ice adhesion and resulting uplift can be avoided
   by using granular backfill around the foundation
   walls or footing pedestals

13
COLLAPSIBLE SOILS

• They are deposits of fine grained particles
  transported by wind and are characterized by
  constituent parts with an open packing
  arrangement, which forms a meta-stable state that
  can collapse to form a closer packed, more stable
  structure of significantly reduced volume.
• Collapse in such deposits can be triggered by
  either increasing the load on the soil or by
  wetting it.
• A collapse condition can lead to structure
  failure, landslides (depending on the
  topography), and tsunamis (if the soil collapses
  into a body of water).

14
A loess avalanche in Shanxi, China which killed
23 people due to structural foundation failure
of small houses on the slope at the foot.
Collapsible Soil LOESS
Other Failures
15
Collapsible Soil LOESS

• Figure 6. Collapse of the soil in The terraces,
  Glenwood, Colorado was causing settlement of the
  concrete retaining-wall foundations

16
Preventive measures and remedies

• By keeping a check on the structural design,
  i.e., loads and foundation selection (mat
  foundations minimize the risk of differential
  settlements)
• Landscape irrigation should be restricted or
  eliminated, excellent drainage facilities should
  be underlain with an impermeable liner to prevent
  water from seeping into the soil
• Popular ground modification treatments for such
  soils include pre-wetting of the soil, dynamic
  compaction, Vibro-floatation, Vibro-compaction,
  Stone/cement columns, treating the soil with
  calcium chloride and/or sodium silicate solutions
  in order to introduce cementing that is
  insoluble, etc.

17
Failure due to Earthquake

• During an earthquake the foundation of the
  building moves with the ground and the
  superstructure and its contents shake and vibrate
  in an irregular manner due to the inertia of
  their masses (weight).
• Damage to foundations structures may result
  from different seismic effects (i) Ground
  failures (or instabilities due to ground
  failures), (ii) Vibrations transmitted from the
  ground to the structure, (iii) Ground cracking,
  (iv) Liquefaction, (v) Ground lurching, (vi)
  Differential settlement, (vii) Lateral spreading,
  and (viii) Landslides.

18
Earthquake Liquefaction

• Lateral movement in soil is possible when there
  is removal of existing side support adjacent to a
  building. There is excessive overburden on
  backfill or lateral thrust on the backside of a
  retaining wall
• Lateral movement is also observed during
  earthquake when structure fails due to lateral
  movement of soil beneath the foundation following
  liquefaction
• Classic examples of such failures are (a) major
  damage to thousands of buildings in Niigata,
  Japan during the 1964 earthquake, (b) Failure of
  Lower San Fernando dam which suffered an
  underwater slide during the San Fernando
  earthquake, 1971.

19
Earthquake Liquefaction

• Figure 7. (a) Building Failure during 1964
  Niigata, Japan Earthquake, (b) Failure of lower
  San Fernando dam in 1971 (c) Retaining wall
  failure (d) Failure of Showa bridge during 1964
  Niigata earthquake in Japan

20
Figure 13. Typical example of overturning of a
building due to liquefaction of the foundation
soil during the Kocaeli earthquake, Turkey,
August 17, 1999, Magnitude 7.4
21
Liquefaction mitigation measures

• Soil Improvement Options
• Densification, Deep Dynamic Compaction
• Hardening Technique, Grouting,
• (ii) Structural Option, Piles or Caissons
  extending below the liquefiable soil
• (iii) Quality Assurance , in taking mitigation
  measures

22
Additional measures and remedies

1. Proper planning of Subsurface Investigation,
2. Analysis and Design and
3. Construction Control and Supervision.
4. For small scale damages underpinning of
   structures is suggested.

23
Construction error

• There are two common sources of construction
  errors, i.e.,
• (I) Temporary protection measures (Error
  relating to temporary shoring, bracings and
  temporary coffer dams),
• (II) Foundation work itself.

24

• Few cases indicating major Construction failure

Foundation not aligned properly
Lack of proper investigation
Punching failure of foundation
25
Construction error

• This paper presents a classic case of poor
  construction practice due to which foundation
  failure of a building in Shanghai, China took
  place

• Figure 9. (a) apartment building was
  constructed, (b) it was decided for an
  underground garage to be dug out. The excavated
  soil was piled up on the other side of the
  building (c) Final failure of building

26
Preventive measures and remedies

• There is no remedy for such massive failures but
  definitely preventive measures in terms of
  supported excavation system for deep
  excavation problems can be adopted to avoid such
  failures.
• Soil nailing is the latest and most widely used
  technique for supporting the vertical excavation
  near an existing building.
• A classic application of soil nailing technique
  is reported in which soil nail support of
  excavation system for the embassy of the Peoples
  republic of China in the United States was
  carried out.

27
Soil Nailing Technique

• Figure 10. (a) Design details of soil nail
  wall section (view from E) (b) work executed for
  supporting vertical excavation using soil nailing
  technique

28
Unequal support

• Footing resting on different type of soil,
  different bearing capacity and unequal load
  distribution will result in the unequal
  settlement or what we call as differential
  settlement.
• The Tower of Pisa in Italy is a classic case
  study.

29

• Figure 11. Different strategies applied to
  prevent the tower from collapse

30
Water level fluctuation

• Rise in GWT reduces the bearing capacity of the
  soil and on the other hand rapid fall in the GWT
  causes ground subsidence or formation of
  sinkholes due to increased overburden effective
  stress value.
• Formation of sinkhole is another major cause of
  foundation failure due to increased water usage,
  altered drainage pathways, overloaded ground
  surface, and redistributed soil.
• According to the Federal Emergency Management
  Agency, the insurance claims for damages as a
  result of sinkholes has increased 120 from 1987
  to 1991, costing nearly 100 million.

31
Figure 12 Formation of sinkhole due to ground
water table fluctuation
32
Vibration effect

• Construction activities such as blasting, pile
  driving, dynamic compaction of loose soil, and
  operation of heavy construction equipment induce
  ground and structure vibrations.
• Ground vibrations from construction sources may
  affect adjacent and remote structures in three
  major ways, i.e.,
• (I) structure vibration with/without the
  effect of resonance structure responses,
• (II) dynamic settlement due to soil
  densification and liquefaction,
• (III) pile driving and accumulated effects of
  repeated dynamic loads.

33
Preventive and remedial measures

• Monitoring and control of ground and structure
  vibrations provide the rationale to select
  measures for prevention or mitigation of
  vibration problems, and settlement/damage
  hazards. Active or passive isolation systems are
  adopted in this regard.

34
Foundation failure slope instability

• Foundation failure due to rapid movement of
  landmass over a slope results when a natural or
  man-made slope on which structure exists becomes
  unstable.
• The major causes of slope instability/ landslide
  can be identified as (i) Steep slope, (ii)
  Groundwater Table Changes / heavy rainfall, (iii)
  Earthquakes and other vibrations, and, (iv)
  removal of the toe of a slope or loading the head
  of a slope

35

• Figure 14. Foundation failure of existing
  facility due to landslide/ slope instability

36
Preventive and remedial measures

• Modifying the geometry of the slope,
• Controlling the groundwater,
• Constructing tie backs,
• Spreading rock nets,
• Providing proper drainage system,
• Provision of retaining walls, etc.
• Soil nailing Technique

37
Foundation failure due to uplift

• One of the major causes of foundation failure due
  to uplift is presence of expansive soil beneath
  the foundation.
• Swelling clays derived from residual soils can
  exert uplift pressures, which can do considerable
  damage to lightly-loaded or wood-frame
  structures.
• In case of pile foundations that are used to
  resist the uplift forces due to wind loads, such
  as, in transmission line towers, high rise
  buildings, chimney, etc., the available uplift
  resistance of the soil becomes the one of the
  most decisive factor in defining the stability of
  foundation.

38
Conclusion

• The paper reviewed and discussed the various
  causes of foundation failure as well as their
  possible preventive or remedial measures through
  case studies.
• The work will be useful for practicing engineers
  in identifying the potential foundation problem
  in advance and taking necessary and appropriate
  action for mitigation purpose.

39
THANK YOU!