subject: On Soft Ground Treatment Methods For The Application - Education Industry [print this page] Abstract: The soft ground treatment quality, the quality of the entire project. Scientific and rational treatment of soft ground, soft ground can reduce and eliminate adverse effects on the upper part of the building.
I combined with concrete examples of the work, focusing on the soft ground treatment of several methods and replacement cushion method in practical engineering foundation design.
Key words: soft ground handling characteristics of replacement cushion
1, Overview. Soft ground is a bad foundation, because the soft soil has low strength, high compressibility and permeability characteristics and weak, so soft on the construction of buildings, must pay attention to the deformation of foundation and stability. Soft foundation bearing capacity and deformation often occur can not meet the design requirements of the problem, so measures are needed to handle it. Ground treatment was designed to improve the bearing capacity, to ensure the stability of the foundation to reduce the compressibility of soft soil, eventually reducing the basis of the settlement and differential settlement, to control the limit permitted in the design.
2, soft foundation treatment works and main
2.1 features of soft ground. Soft soil, including mud, silty soil, red fill, mixed fill and loose saturated fine sand and silt, this type of soil as a foundation, the safety of the project is detrimental to the performance of the engineering properties of the natural high water content, porosity ratio, high compressibility, permeability, low shear strength. How to ensure that buildings built on weak foundations, the stability, has always been a very important Technology Subject.
2.2 soft ground treatment method. Currently, the main methods of soft ground treatment are: for cushion method; drainage consolidation; compaction method; deep mixing; grouting; dynamic compaction.
3, replacement cushion for design applications
Basis during the design of buildings, frequently encountered soft ground treatment of the question, "replacement cushion method" is used widely in approach, the following combination of practical engineering experience to analyze and explain.
"Building foundations technical specifications" (JGJ79-2002) provides: replacement method suitable for mud, silty soil, loess, Earth Fill, Fill foundation and underground drain, dark ponds, shallow layer processing. Although the cushion of different materials, the stress distribution is slightly different, but test results of its carrying capacity is quite close; by subsidence observation data showed that the characteristics of different materials similar cushion, it can be of various materials cushion designed cushion of sand are similar calculation by the calculation. But on loess, soil, seasonal frozen soil and other special processing by soil replacement, its main purpose is to eliminate handling wet soil subsidence, swelling and frost heaving, so to be considered in the design should be the key to solving the problem is different. Replacement cushion cushion design including the determination to be the minimum width and thickness.
Had a four-story brick office building, strip foundation under load-bearing walls, width 1.3 m, depth 1.1 m, the upper base of the load acting on the building for the 120KN / m, based on average weight degree 20KN/m3. For the silty clay soil surface, thick 1m, severe as 17.5KN/m3; second silty clay layer is thick, 15m, severe as 17.8KN/m3, water content w = 65%; foundation bearing capacity value of 45kPa ; third layer dense sand and gravel. Groundwater Jude Biao as 1m, because the soil is weak, can not afford the building load, by comparison of several programs, can be decided directly by artificial replacement cushion method of construction, the building foundation treatment. In the cushion material, use of sand as bedding, its design value of bearing capacity calculated by f = 180KN/m2 (construction of the sand cushion density control in the secret level), severe take = 19.5KN/m3.
