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S.M.E.C
(Soil & Foundation
Engineers)

STONE COLUMN TESTING METHODOLOGY

Posted By: Admin
 2019/08/12

  1.  

METHODOLOGY FOR CONDUCTING

IN-SITU STONE COLUMN TEST

 

     

list of contents                                                                    SHEET NO

 

 

1.0     General                                                                                        3
         
2.0     Apparatus Require                                                                        3
 
3.0     Test Procedure                                                                             3 – 4
 
4.0     Nature of Test                                                                               4
 
5.0.    Method of Loading                                                                        5.
 
6.0     Details of Proposed Load Tests                                                      5
 
7.0     Details of loading Platform/ kenteledge                                           6
 
8.0     Load test (In Verticle Compression)                                                6
 
9.0     Application of Load                                                                        7
 
10.0    Settlement and Observations                                                         7
 
11.0    Report                                                                                          7
 
12.0    Format for recording of field test data                                             8
 
13.0    Increment load Chart                                                                     9
 
14.0    Sketch of Test Set up                                                                    10



METHODOLOGY FOR IN-SITU STONE COLUMN TEST

 

1.       GENERAL:

 

This test conducted to check the improved soil after ground improvement using stone columns. This test shall be carried out at the foundation depth. A format for recording test information is enclosed. A report of testing shall be submitted after the completion of test and this shall also include the plot of the settlement of plate & pressure on plate, test details, together with an evaluation of the test results.

 

2.       APPARATUS REQUIRED :

 

(a)      Loading Platform: - Kent ledge of sufficient size and properly design members so as to estimate load reaction for conducting the test shall be used.

 

(b)      Hydraulic Jack: - Hydraulic Jack of required capacity with properly calibrated load measuring devices, such as pressure gauges shall be used.

 

(c)      Bearing Plate: - Square bearing plate of mid steel of 25 mm in thickness and varying in size from 4.0 m to 0.60 m shall be used.

 

(d)      Settlement Measuring Device: - 4 Nos. dial gauges with 50 mm travel, capable of measuring settlement to an accuracy of 0.01 mm.

 

(e)      Datum Bar: - Beam or rod of sufficient strength capable of maintaining straightness when fitted on two independent supports fitted with arms or magnetic bases for holding dial gauges.

 

3.       TEST PROCEDURE:

 

The test shall be conducted as per IS: 15284: 2003 – Part-1.



(a)      Selection of Location:

 

The location for load test shall be decided by client and shall be conducted at an elevation of the proposed foundation level.

 

(b)      Test Pit:

 

(i)       While using the plate size of 3.55 m x 3.55 m, the size of the pit will be  6.50 m x 6.50 m and while using the plate size of 2.04 m x 2.04 m, the size of the pit will be  5.00 m x 5.00 m

 

(ii)      The depth of the pit shall be the same as the depth of actual foundations or specified.

 

(c)      Dead Load:

 

The dead load of all the equipment used shall be recorded prior to application of load increment.

 

(d)      Plate Size And Thickness:

 

For Routine Test on Single column – 2.04 m2 size plate of 25 mm thickness shall be used for conducting test

For Routine Test on Group column – 3.55 m2 size plate of 25 mm thickness shall be used for conducting test

 

(e)      Placing of Test Plate:

 

Plate shall be added to the soil by spreading fine sand in a layer not exceeding 5 mm carefully leveled and set horizontally at the bottom of the pit. A minimum seating pressure of 70 g/cm2 shall be applied and removed before starting the load test.

 

(f)       TEST ARRANGMENT:

 

The test plate shall be placed over a fine sand layer of maximum 5  mm thick, so that the center of plate coincides with the center of the girders. The hydraulic jack should be placed centrally over the plate with the loading column in between jack and the reaction beam so as to transfer load to the plate. A minimum seating pressure of 70 g/cm2 shall be applied and removed before starting the test.

 

The two supports of the reference datum bar shall be placed over firm ground.



4.0     NATURE OF TESTS:

 

Irrespective of the method used for construct the stone column, the routine load test on the top of a single column is conducted to evaluate the load-settlement behavior of the stone column.

 

5.0.    METHOD OF LOADING:

 

The reaction method of loading thru dead load shall be employed. In this method, loading is done by a jack against a reaction of loaded platform as detailed below-

 

6.0     DETAILS OF PRPOSED LOAD TESTS

 

 

 

WORKING STONE COLUMN

Details

Routine Group Column Load test

Routine Single Column Load test

 

Stone Column

900 mm dia at 2.2 m center to center spacing

 

Max. Design Loading Intensity

20.00 T/m2

Effected Area of Soil around the each column

3x(3.14/4)x(D)x(D)

=12.57 m2

(3.14/4)x(D)x(D)

=4.19 m2

 

D= diameter of Effected area of the stone column

= 1.05 x spacing between stone columns

 

Dimension of Plate

Square = 3.55 m

Circular= 4.00 m

Square = 2.04 m

Circular= 2.31 m

 

Max. design load on the steel plate

20.0 t/ m2 x area of plate

=20.0 t/ m2x 12.57 m2

=252 T

20.0 t/ m2 x area of plate

=20.0 t/ m2x 4.19 m2

=84 T

 

Test Load

1.1  x design load

= 1.1 x 252 = 277 T

1.1x design load

= 1.1 x 84 = 92 T

 

Kenteledge Load (1.3 times the test Load)

1.3 x Test load

= 1.3 x 277=360 T

1.4 x Test load

= 1.3 x 92=120 T

 




7.0     DETAIL OF LOADING PLATEFORM/ KENTLEDGE:

 

(a)      Main Girder             –        IS MB 600 (2 No. of 8.0 M long)

 

(b)      Second Girder         –        IS MB 450 (12 No of about 10.0 m long)

 

(c)      Bearing Plate          –        For Single Column Test

2.04 m2 & 25 mm thick MS Plate

 

For Group Column Test

3.55 m2 & 25 mm thick MS Plate

 

(d)      Loading Column      –        Adjustable Size

 

(e)      Dial Gauges            -         Least count -0.01 mm and Max travel-50 mm

 

(f)       Pressure Gauge      -         Least Count -10 Kg/cm2

 

(g)      Density of Filling Material (Excavated Soil) – assumed 1.4T/m3

 

Above mentioned details are tentative and the same will be confirmed 3 days prior to the load test

 

Calibration certificate of all the equipment will be submitted within 3 days prior to the load test

 

8.0     LOAD TEST (IN VERTICAL COMPRESSION):

 

In routine load test [In vertical compression] on the top of sngle/group of three no column is tested up to 1.1 times the designed safe load. The test load is applied through a Hydraulic jack and the applied pressure is recorded from a pressure gauge attached to the Hydraulic jack through a pumping unit. Whereas the load is applied in stages and settlement is recorded through 4 Nos. dial gauges positioned at an angle of 90 degree to each other around the top area of the column and held by datum bars resting on immovable supports. After each stage of increment the load is maintained till the rate of settlement less than 0.05 mm/h. The reaction for load test is taken through a kentledge made of a set of girders and dead load placed above the same in the shape of a platform.

 

This test is conducted by maintained load method as per the IS: 15284 (Part – I) by applying a series of vertical downward incremental load of near about 1/5 of design safe load. Each loading stage is maintained till displacement rate of the column top less than 0.05 mm/h. After reaching of the maximum load the test load is maintained for 12 hrs. After that the unloading is done in the same stapes as loading.



9.0     APPLICATION OF LOAD:

 

(a)      Loading shall be carried out in increments of 1/5 estimated ultimate bearing capacity.

 

(b)      Loading shall be carried out till one of the following conditions occur-

 

For Single Stone Column Test- whichever occurs earlier

 

Total settlement of the plate exceeds 10 – 12 mm.

or

Load intensity 92.0 T

 

For Group Column Test- whichever occurs earlier

 

Total settlement of the plate exceeds 25 -30 mm.

or

Load intensity 277.0 T

 

10.     SETTLEMENT AND OBSERVATION:

 

(a)      Settlement shall be recorded with four dial gauges.

 

(b)      Settlement shall be observed for each increment of load after an interval of 1, 2:25, 4, 6:25, 9, 16, 25 minutes and thereafter at every hourly interval.

 

(c)      The next load increment shall be applied when the rate of settlement is less than 0.05 mm/hr. For computing the rate of settlement its extrapolation for period less than one hour shall not be permitted.

 

UNLOADING:

 

(a)      Unloading shall be done in at least 4 stages in about 1 hour in the same manner as was done during the application of load. Rebound observations during the unloading also shall be noted.

 

Rebound shall be noted during unloading stages till the readings become reasonably constant.

 

11.0    REPORT:

 

The continuous listing of all time, load and settlement data, for each test shall be recorded with details of test elevation, natural water table, profile of test pit, size of bearing plate and irregularity, if any, in routine procedure.


 

SHREE MAHAVEER ENGINEERING CONSULTANTS

LOAD TEST

SHEET NO:

CLIENT

:

 

PMC

:

WORK REF

:

 

TEST LOCATION

:

TEST NO

:

 

TYPE OF TEST

:

SIZE OF PLATE

:

 

ULTIMATE BEARING CAPACITY

:

TEST LEVEL

:

 

NATURE OF TEST

:

LOAD APPLIED UPTO

:

 

STONE COLUMN ID NO

:

LC OF DIAL GUAGE

:

 

DEPTH OF TEST

:

 

 

 

DATE OF TESTING

:

 

 

Date

Clock Time

Reading Interval Time

Load in kg/cm²

Load in Ton

Dial Gauge Reading (mm)

Average Settlement (mm)

Rate of Settlement

Remarks

A

B

C

D

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

For Shree Mahaveer Engineering Consultants

For  

For AWHO

 


 

SHREE MAHAVEER ENGINEERING CONSULTANTS

PROJECT:

LOAD TEST

LOAD INCREMENTS CHART

Ram Dia of Hydraulic Jack

:

 

cm

Area of Ram for Hydraulic Jack

:

 

cm2

Least Count of Pressure Gauge (1 Div)

:

 

KG/ cm2

Load Applied against one Division

:

 

MT

Test Plate Size & Area

:

 

m2

Required Safe Design Load

:

 

MT/ m2

Safe Design Load on Test Area

:

 

MT

Test Load for Routine Test

:

 

MT

Increament Load 20% of Safe D/Load

:

 

MT

Applied Load for Each Step (Actual) Div.

:

 

MT

Description

Theoritical Load

Actual Applied Load for Test

Load

Load

Load

(In MT)

(In KG/ cm2)

(In MT)

(% of D/Load)