• 메뉴전체보기
  • 홈
  • Home > BUSINESS > Soft ground Treatment
  • Teneral of soft groune
  • What is soft ground??
  • Soft ground means the ground that does not have enough bearing power of building and structure on it. It is not called Soft Ground even no enough bearing power when the building on it is not heavy because it can be used without improvement. But when the building or construction is heavy, even the ground is harder than other area, we call it Soft Ground.
  • Accordingly, the Soft Ground is not decided by the hardness of ground but by the relativity of structures on it.
  • Generally, the Soft ground is consists of fine grains like clay, silt or organic silt that has big pore or soil layer of loose structure. Also the ground of high underground water level and the ground that holds problem settlement of structure on it and subsidence called as soft ground.
  • As a conclusion, the Soft ground is not decided by ground condition. It is decided considering structure details, shape, scale, character of ground and construction condition of structure on it.
  • Saturated clay Ground
  • Sandy ground with loose structure
  • Ground with high portion of manure ingredient
  • Reclaimed area on river / sea
  • Reclaimed area by rubbish
Soil Thickness of Soft ground N Value qc(kg/cm2) qu(kg/cm2)
Clay / Manure Less than 10m Under 4 Under 8 Under 0.6
Over 10m Under 6 Under 12 Under 1.0
sandy - Under 10    

※Above table shows only general standard. For exact assessment,
   1) Character of strength of underground
   2) banking height
   3) banking condition
   4) Thickness and consolidation of clay layer
   5) importance of structure on it should be considered.
  (qc : Single mandrel compressed strength of soft ground layerqu : Cone index of soft ground layer)

  • Stability problem (bearing capacity & movement)

- Due to low shearing stress, the stability problem can be easily occurred

  • Subsidence problem (excessive subsidence)

- Water containing rate of alluvial soil will be around 100% when loaded. The ground start subsidence by decrease of volume of water in ground

  • Friction problem

- The base pile can be broken by friction when the subsidence of soft ground become deeper than pile top.

  • Liquid phase problem

- The saturated sandy, silty ground has unsuitable structure. Its volume and strength will be suddenly decreased by force of earthquakes, strong waves and vibration. By the impacts of those factors, the excess pore pressure will be increased. Then the bearing capacity shall be around 0 and becomes liquid like muddy water.

  • Permeability problem

- The loose sandy ground can cause the 1) liquid phase 2) demolish of dam by boiling & piping phenomenon which happened by Quick Sand phenomenon.

Method Details Effectiveness
Surface Treatment PP Mat, Mixed surface treatment, surface drainage, sand mat
Transformation Excavation, Compulsory exchange, Blast exchange
Banking Pressure Banking Pressure, Easy slope
Banking reinforcement Banking reinforcement
Load Reducing Light banking
Slow loading Steady loading, Step loading
Re-Loading Bank loading, Air pressure loading, Ballasting under ground water
Vertical Drainage S.D / PBD / PCD / P.D
Sand Pile Sand Compaction Pile
Compaction Vibro-Compaction, Lot tamping, Dynamic Compaction
Concreting Mixed treatment in deep area, Gypsum pile, Concrete injection, Freezing
Structure Pile, Board pile, Culvert (concrete structure)
.
1