Spec Section2 StoneColumns Dry&Wet MethodV1 CPT Ver3

8/12/2019 Spec Section2 StoneColumns Dry&Wet MethodV1 CPT Ver3

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SECTION 2 - STONE COLUMNS

1.0 GENERAL

The Contractor shall construct stone columns of nominal diameter of 1.0m. The stonecolumn shall extend below the specified installation level to the specified depth. Stone

columns may be installed using the wet or the dry method in accordance with thespecifications.

2.0 STANDARDS AND DEFINITIONS

British Standard Specifications

All materials and wormanship shall be in accordance with the appropriate currentBritish Standards except that where the re!uirements of British Standards are in conflictwith this specification" the latter shall tae precedence.

3.0 SPECIALIST SUBCONTRACTORS

#nstallation of stone columns shall be carried out by specialist contractors e!ual to thetas. The Specialist contractors shall

$i% have successfully carried out stone column installation of a similar naturepreviously&

$ii% possess e!uipment for installation stone columns and for instrumentationre!uired in this contract.

4.0 PERSONNEL

The Specialist contractor shall employ sufficient numbers of personnel experienced ande!ual to the tas of the type of stone column installation described in this contract.

5.0 TOLERANCES

'.1 S(TT#)* +,T

Setting out shall be carried out from reference lines and points shown in the -rawings.#mmediately before installation of the stone column" the stone column positions shall beestablished by surveys.

'. -(/#AT#+)

The maximum permitted deviation of each stone column shall be

$i% ori2ontal deviation of the centre of the stone column from the position shownon the -rawings '0mm&

$ii% /erticality 1 percent.

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6.0 PRETREATMENT ASSSESSMENT

The contractor shall carry out Cone 3enetration Tests $C.3.T.% prior to commencement ofthe treatment wors to confirm the treatment wors design. The locations of the C.3.Ttests shall be instructed by the (ngineer.

Cone resistance shall be related to 4elative -ensities using the approved relationships

between cone resistance and relative densities.

7.0 COMPACTION ASSESSMENT FROM TRIAL STONE COLUMNS

)ine $5% numbers of stone columns shall first be installed on a s!uare grid based on apreliminary spacing to be instructed by the (ngineer from evaluation of the pretreatmentC.3.Ts. Two $% numbers C.3.T. shall be carried out at mid points between stone columnsto assess the improvement in relative densities due to the stone column treatment. The(ngineer shall after evaluation of the post treatment C.3.T.s confirm the spacing of thestone columns for the particular area.

8.0 DAMAGE TO STONE COLUMN

The Contractor shall ensure that damage does not occur to completed stone columns.

The Contractor shall inform the (ngineer his proposed se!uence and timing forconstructing stone columns having regard to the avoidance of damage to ad6acentstone columns.

9.0 DIAMETER, SPACING, LENGT, AND LE!ELS OF STONE COLUMNS

The diameters" spacings" lengths and installation levels of the stone columns shown onthe -rawings are provisional sub6ect to confirmation on site.

10.0 STONE CONSUMPTION

The consumption of stone bacfill shall not be less than 0.78''cu.m. per linear m. ofstone column.

The rate of stone consumption shall be assessed by averaging the stone used over thelength of each stone column. The Contractor shall provide sufficient nos. of steelbins9containers9hoppers of fixed dimensions" instrumentation and all means for accuratemeasurement of stone volumes.

11.0 OBSTRUCTIONS

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#n the event of obstructions preventing the penetration of the vibroflot the Contractorshall carry out any of the following

$i% 4eposition the stone column a short distance from the original position&

$ii% Additional stone columns around the obstruction&

$iii% 3reboring.

12.0 MATERIALS AND MATERIALS TESTING

Stones used for forming stone columns shall consist of hard" durable and inert material.The particle si2e distribution ranging from 1'mm to :mm or such larger si2es as maypass through the access tube for the dry method" and between ' and 7'mm for thewet method with an allowable tolerance of 1; passing by()T

1:.1.1 Bottom eed /ibrators

The Contractor shall adopt only Bottom eed /ibrators whereby

$i% stones9gravels are conveyed to the tip of the probe using an eccentrictube attached to the probe&

$ii% air pressure is used to facilitate penetration and movement of stones9gravelsthrough the tube to the probe tip&

Air pressure in $ii% above shall be lower than 003a or limited to such levels as toprevent fracturing of the in


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The vibroflot shall be sufficiently powerful to ensure

$i% The depths indicated in the -rawings may be reached&

$ii% /erticality of the stone columns&

$iii% Ade!uate treatment of the areas surrounding the treatment point to a minimum

distance of 0.8m from the centre of the stone column.

$iv% Ade!uate compaction of the stones.

The vibroflot shall be e!uipped with automatic systems for continuous record asdescribed in subclause 1:..

1:. #)ST4,>()TAT#+)

The e!uipment to be used shall be instrumented with sensors and the data processedby a microprocessing unit to enable continuous monitoring and data capture of

$i% -epth of vibrator and vibrator movements&

(ii) 3ower consumption&

during construction of each stone column.

-ata captured shall be continuously displayed on an C- unit and output on paperprinter throughout the process of stone column construction for submission to (ngineer.

1:.: 34+C(-,4( +4 C+>3ACT#+) + ST+)( C+,>)S

The procedure for forming and compacting stone columns shall generally be asdescribed hereunder to be agreed with the (ngineer on site after the carrying out offield trials.

3ower consumption shall form a basis for determining the ade!uacy of compaction ofstone columns.

The minimum power consumption at each level shall not be less than that determinedfrom the preliminary stone column installation.

$i% ,nless otherwise specified penetration of the vibroflot to the re!uired depth shallbe with air 6etting and9or vibrations with the stone tube filled with stones.

$ii% Compaction shall generally be as follows

The vibroflot shall be raised by about 0.'m to 1m and stones released into thehole and then repenetrated into the hole to laterally displace the stone andsimultaneously compact the stone and surrounding soil until the re!uired powerconsumption determined from installation of the preliminary stone columns isachieved.

1D.0 #ET METOD

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1D.1 /#B4++T

The vibroflot $poer vibrator% shall be sufficiently powerful to ensure

$i% The depth indicated in the -rawings may be reached&

$ii% Ade!uate compaction of the stones.

The vibroflot shall be e!uipped with automatic systems for continuous record of poweroutput and depth of penetration.

1D. #)ST4,>()TAT#+)

The e!uipment to be used shall be instrumented with sensors and the data processedby a microprocessing unit to enable continuous monitoring and data capture of

$i% -epth of vibrator and vibrator movements&

(iii) 3ower consumption&

during construction of each stone column.

-ata captured shall be continuously displayed on an C- unit and output on paperprinter throughout the process of stone column construction for submission to (ngineer.

1D.: 34+C(-,4( +4 C+>3ACT#+) + ST+)( C+,>)S

The procedure for forming and compacting stone columns shall generally be asdescribed hereunder to be agreed by the (ngineer on site after the carrying out of fieldtrials.

3ower consumption shall form a basis for determining the ade!uacy of compaction ofstone columns.

The minimum power consumption at each level shall not be less than that determinedby the (ngineer from the preliminary stone column installation.

$i% ,nless otherwise specified penetration of the vibroflot to the re!uired depth shallbe with water 6etting and9or vibrations. +n reaching the re!uired depth" thevibroflot shall be lifted and lowered at least once over the full depth fromcommencement level to the re!uired depth&

$ii% Compaction at any depth shall be as follows

(a) Compaction with the vibroflot ept at that depth for not less than : min. whilestones are fed in. Any arching of the stones between the vibroflot and thesides of the hole shall be overcome by raising and lowering of the vibroflot.

(b) =ithout further input of stone" the vibroflot shall be raised in steps of about1m and repenetrated into the hole to laterally displace the stone and

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compact the stone and surrounding soil to achieve the re!uired powerconsumption determined from installation of the preliminary stone columns&

(c) #nput of stones shall be resumed and the procedures given in sub

Documents

Spec Section2 StoneColumns Dry&Wet MethodV1 CPT Ver3