Stone columns

In soils containing strata of silt and clay, those strata may not densify and the overall deposit may not benefit from vibroflotation. However, the probe will create a zone of displaced material which can be filled from the surface with stone aggregate as the probe is withdrawn. These stone columns can then be used for structural support. This process is often referred to as vibro-replacement. Table 3.3 and Fig. 3.8 shows the vavious soils for which vibro-treatment is effective. 

Redun consolidatiDr, setllecnent Precompression Stone columns Jetgrouling Deep soil mixing Compaction oroutinci Electro-osmosis... 

Shenthan, T. (2001). Factors affecting liquefaction mitigation in silty soils using stone columns. MS Thesis, Department of Civi, Structural and Environ. Eng., University at Buffalo, NY, USA. 

Ayadat, T. and Hanna, A.M. 2005. Encapsulated stone columns as a soil improvement technique for... 

Cooper, M.R. and Rose, A.N. 1999. Stone column support for an embankment on deep alluvial soils. Proceedings Institution Civil Engineers, Geotechnical Engineering, 137,15-25. 

Universiti Tun Hussein Onn Malaysia (UTHM) sits on deep deposit of soft marine clay with low strength and high compressibility. Pre-treatment of the soil by ground improvement is necessary before construction works can commence on these grounds. Various ground improvement techniques are available in the market, such as vertical drains with surcharge, stone columns, mass replacement, stabilisation, etc. 

Densify the loose, liquefiable soil layer. Stone column is often satisfactory if the loose layer is mostly sand. Other approaches, such as jet grouting, deep soil mixing with cementing agents and in situ vibratory densification can all be used. If the liquefiable soil layer is close to the ground surface, a complete excavation and replacement with compacted engineering fill is sometimes also feasible. 

Stone columns or piles provide migration pattiway through... 

It is important during any ground gas assessment to consider whetiier tire data is representative of as-built conditions. For example, is there a surface clay layer overlying a gas source that will be penetrated by stone columns or piles tiiat allow gas to migrate to surface This is common on sites with alluvium where a clay layer overlies peat deposits at depth. In this case any assessment needs to consider the gas regime in the deeper source and how gas will migrate up the stone columns. 

Can also be installed as stone columns using ground improvement plant... 

A comparison of cases (b) and (d) explains the paradox that a stone column resting on three equally spaced supports has a greater tendency to fracture under its own weight than when only two supports at the ends are... 

As in the development of other areas of engineering, mathematics has played an important role in the development of the safety and reliability fields in the oil and gas industry too. The history of mathematics may be traced back to the development of our currently used number symbols, often referred to as the "Hindu-Arabic numeral system" in the published literature [1]. Among the early evidence of the use of these numerals are the notches found on stone columns erected around 250 bc by the Scythian Emperor of India named Asoka [1]. 

Introduction 7.6.2 Soil removal and replacement 7.6.3 Stone columns ... 

The stone column technique comprises the insertion of compacted columns of granular material into the soils to be treated. These columns displace the existing deposits and are tightly interlocked with the surrounding soil. 

Execution of stone columns by the vibro-replacement technique... 

To construct stone columns, a vibro-flot (see Section 7.5.3.3) is allowed to penetrate to the design depth and the resulting cavity is during retrieval of the probe filled with gravel or crushed rock, free of clay and silt. Several techniques have been developed to install stone columns in soils with different groundwater levels, ranging from completely saturated (wet, top-feed process) to dry (bottom-feed process). 

For design aspects related to stone columns reference is made to Priebe, 1995. 

Stone columns increase the shear strength and stiffness of soft, cohesive soil strata and can also be used to improve the resistance of granular soils against Uquefaction. 

Stone columns are not suitable in soft soils having a very low undrained shear strength since the lateral support for the columns may be too small. This can result in lateral bulging of the columns. 

A high area replacement ratio (i.e., ratio of the area occupied by stone columns to the overall area of the improved ground) may cause heave of the... 

In order to improve the shear strength, the bearing capacity and consolidation behaviour of soft subsoil layers, stone columns or sand compaction piles can be used. If necessary, they can be installed from floating equipment. 

Alternatively, the drainage capacity, and consequently the strength, can be improved by installing vertical drains. Also stone columns or piles may be installed to transfer foundation loads to more competent layers underneath the peat. 

Massarsch, K.R. Deep Soil Compaction using Vibratory probes, ASTM symposium on design, construction and testing of deep foundation improvement stone columns and related techniques, ASTM STP, R.C. Bachus Edt, 297-319, 1991. 

Sinopoli A (1989) Dynamic analysis of a stone column excited by a sine wave ground motion. Appl Mech Rev Part 2 44 246-255... 

The presence of stone columns, timber piles, and other stiff elements provide additional shear resistance against earthquake shaking. These reinforcements would take much of the earthquake load, thereby minimizing the shear deformation of the soil. 

As shown in Fig. 8a, when the tunnel experiences uplift due to flotation, the liquefied soil moves underneath the displaced tunnel and lifts it further up (Schmidt and Hashash 1999). Uplift can be prevented through isolation using cutoff walls, such as sheet pile walls stone columns (Fig. 8b) or jet grout columns (Fig. 8c). Sheet piles with drainage capability can also reduce excess pore water pressure. The rise in excess pore water pressure is prevented at the bottom of the tunnel and in the soil underneath with these barrier walls. With longer barrier walls and a wider structure, uplift is more difficult. After the UquefacticHi potential is mitigated, flexible joints can be used to allow for differential displacements at tunnel connection joints. 

For cases in which the available construction time is limited or serviceabiUty criteria are high, methods other than basal-reinforced embankments need to be chosen. Most commonly, ground improvement using stone or gravel columns is chosen. However if the foundation soil is extremely soft, the use of conventional stone columns can lead to unacceptable deformation or even failure. This is because the soft soil... 

The latter input is described similar to ground improvement with stone columns by an area ratio a and can be calculated using Eq. [16.1] (Fig. 16.4) ... 

Vertical bearing members used for such stmctures are considered uncompressible therefore, typically concrete piles, timber piles, concrete columns, or grouted stone columns have been used. Geosynthetic reinforcement is typically required to have high... 

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