Soil improvement and construction methods in peat - Geotechnics of Organic Soils and Peat - page 142

Figure 6.19 Vacuum grouting injection process and equipment. The plastic cover is used to suck in all
the entrapped air so as to have no void space ( after Balvac, 2008).
liquid is introduced either through injection pipes set at appropriate intervals and
depths or over the surfaces and into the structure through cracks, fissures and porous
areas. Figure 6.19 shows the process of vacuum grouting injection.
6.4.5 Dry jet mixing system (DJM)
The second type of jet grouting system is the dual phase system (DPS). One of the
most commonly used methods in DPS is dry jet mixing system (DJM). This is a highly
effective ground treatment systemused to improve the load performance characteristics
of soft clays, peats and other weak soils. The concept of using a dry binder for deep
soil mixing was first presented in 1967 by Kjeld Paus from Sweden. Thirty years have
passed since then and the technique has evolved considerably. The method is based on
injecting dry binder carried by compressed air into soil. DJM uses mixing blades to
mix dry reagents, such as cement or lime, with in situ soils for remediation (Kazemian
and Huat, 2009b).
In this method, the process employs the effects of both hydration and the bonding
of soil particles to increase the shear strength and reduce the compressibility of the soil
mass (Keller Holding, 2005).
6.4.6 Dynamic replacement method
Another deep stabilization method is the dynamic replacement (DR) method. The
process consists of dropping heavy weights (ranging from 10 tons to 15 tons) from
heights of 10m to 15m to form large diameter granular columns in cohesive soil
deposits. Subject to the site working conditions, the nature and consistency of the soil
conditions and the required length of the DR columns, it may be required to perform
pre-excavated DR columns (Sin, 2003). The size of the excavated crater may be 2
to 3m deep over an area of 4m 2 . Very often, the actual size of this pre-excavated
DR crater is governed by the ground water table condition. After the excavation, the
crater is filled with granular materials and a series of pondering and ballasting phases