Geotechnical & Material Testing Laboratory - NHAI

Index 1.OBJECT.............................................................................................................1 2.INTRODUCTION.................................................................................................1 3.SCOPE OF WORK:...............................................................................................2 4.EXPLORATION PROGRAMME:...............................................................................2 5.METHODOLOGY OF FIELD INVESTIGATION:...........................................................4 5.1.Boring:...........................................................................................................4 5.2.Sampling:.......................................................................................................4 5.2.1.Disturbed Sampling (DS):..............................................................................4 5.2.2.Undisturbed Sampling (UDS):.........................................................................4 5.2.3.Transportation and storage of samples:...........................................................5 5.3.Standard Penetration Test (SPT):......................................................................5 5.4.Drilling in rock:...............................................................................................6 5.5.Ground Water Level Measurement:....................................................................7 6.STANDARDS AND GUIDELINES FOR FIELD INVESTIGATIONS:..................................7 7.GEOTECHNICAL LABORATORY TESTING:...............................................................8 8.GEOTECHNICAL ASSESSMENT AND FOUNDATION FEASIBILITY.................................. ...........................................................................................................................9 8.1.DEPTH OF FOUNDATION...................................................................................9 8.1.1.FOUNDATION IN SOIL...................................................................................9 8.1.2.FOUNDATION IN ROCK................................................................................11 9.OPEN/ SHALLOW FOUNDATIONS IN SOIL............................................................11 9.1.Net safe bearing capacity from shear consideration:...........................................11 9.1.1.For Clay Soils (Φ = 0):................................................................................11 9.1.2.For C - Φ soils:...........................................................................................11 9.1.3.Reduction Factors:......................................................................................12 9.2.Net Safe Bearing Capacity:.............................................................................12 9.3.Determination of Safe Bearing Capacity (SBC) from SPT 'N' value considerations...12 10.PILE FOUNDATIONS........................................................................................15 10.1.Capacity of Piles in Intermediate Geo-material and Rock:..................................15 10.2.Ultimate Capacity of Pile in Soils:...................................................................17 10.3.Lateral Capacity of Pile..................................................................................18 11.SUMMARY OF FOUNDATION DETAILS:...............................................................20 12.LIMITATIONS:................................................................................................25 ANNEXURE Individual Reports of all Structures

Preparation of Detailed Project Report for Up-gradation of Ausa – Waranga & Wardha – Butibori Section of NH361 in the state of Maharashtra.

FINAL DETAILED PROJECT REPORT SUB SOIL EXPLORATION & ANALYSIS REPORT WARDHA-BUTIBORI

SUB SOIL EXPLORATION & ANALYSIS REPORT 1. OBJECT Conducting detailed Subsoil Investigation and recommendation of Net Safe Bearing Capacity (SBC) for various structures of Ausa-Waranga & Wardha - Buttibori section of NH361 in the state of Maharastra. The entire project awarded consists of following four packages:

•

Ausa – Chakur (58.2 km)

•

Chakur – Loha (61.8 km)

•

Loha – Waragaphata (70.7 km)

•

Wardha-Butibori (60 km)

The present report consists of detailed engineering services for Wardha – Buttibori section (NH – 361) from Km 85+300 to Km 28+800 (i.e., Salad to Butibori). This Report Consists of: 

Introduction



Scope of work



Methodology of subsurface Investigation



Sub soil profile



Analysis & sample Design



Foundation Recommendations

2. INTRODUCTION This report presents the results of field explorations and Geotechnical engineering studies performed for proposed major bridges (MJB), minor bridges (MIB) and vehicle underpasses (VUP) in various predetermined locations. The purpose of the explorations

and

studies

is

to

identify

subsurface

conditions

and

formulate

Geotechnical recommendations for design and construction. The main text of the report includes description of field explorations, laboratory testing, subsurface conditions, conclusions and recommendations based upon review of existing data, engineering studies and analysis. Field and Laboratory works are conducted based on Indian Standard specifications and, as per the requirement of project.

1



3. SCOPE OF WORK: The scope of subsoil Investigation is to ascertain Geotechnical and geological properties of substratum for design and construction of various types of foundations. It is proposed to have exploration by drilling of boreholes at various locations of given structures. Accordingly the exploration program of boreholes are taken upto a maximum depth of 19.5 m or 3 m into hard rock whichever occurs earlier. Undisturbed, Disturbed and Rock samples were collected appropriate to ground conditions and transported them to Geotechnical laboratory. Laboratory tests are conducted to determine the Index and Engineering properties of soil, rock and suggested the Net Safe bearing capacity of the soil on which structures are to be constructed.

Engineering analysis was carried out for recommending the location

and Net Safe Bearing Capacity of foundation for the proposed structures. 4. EXPLORATION PROGRAMME: Sub-Soil Investigation Plan S. No. Existing chainage

Type of Structure

No of Boreholes

1

28+750

523+305

Half Trumpet

2

2

36+233

517+060

4 Lane VUP

1

3

38+853

514+515

MIB

1

4

39+810

513+566

MIB

1

5

43+607

509+760

MIB

1

6

43+905

509+462

MIB

1

7

44+830

508+583

MIB

1

8

45+789

507+773

2 Lane VUP

1

9

47+126

506+316

MIB

1

10

49+552

503+860

MIB

1

501+930

2 Lane VUP

1

501+093

MIB-2

1

11 12

Kelzar Bypass

13

55+052

498+449

MIB

1

14

56+979

496+428

MIB

2

15

58+550

494+892

MIB

1

493+270

Major Bridge

5

493+132

MIB-2

1

492+914

MIB-1

1

492+204

2 Lane VUP

1

487+542

MIB

1

16 17 18

Seloo Bypass

19 20

2

Proposed Chainage

65+961


S. No. Existing chainage


Proposed Chainage

Type of Structure

No of Boreholes

21

67+122

486+368

MIB

1

22

67+725

485+759

MJB

9

23

72+328

477+600

2 Lane VUP

1

24

76+650

474+016

2 Lane VUP

1

25

Salod realignment

471+516

ROB

2

26

Salod reallignment

468+038

4 Lane VUP

1

Field Tests



Standard Penetration Test (SPT) was conducted at every 1.5m depth interval in boreholes as per IS: 2131-1981.



Disturbed Samples (DS) and undisturbed Samples (UDS) were collected as per IRC 78 – 2000 guidelines



Drilling in soft rock, weathered rock and in hard rock was carried out by diamond core drilling method using double tube core barrels of Nx size and obtained the rock cores.



Ground Water table was observed in each bore hole as per IS : 6935 - 1973

Following Laboratory Tests are Conducted on selected samples of Disturbed and Undisturbed soil samples



Moisture content & Specific Gravity



Bulk Density



Grain Size Analysis



Atterbergs Limits



Free Swell Index



Triaxial Shear Properties – Cohesion, C and Friction Angle, Φ

Following Laboratory Tests are Conducted on selected Rock samples 3




Moisture content, Porosity & Density



Specific gravity



Uniaxial Compression test


5. METHODOLOGY OF FIELD INVESTIGATION: The field exploration methods, sampling requirements, types and frequency of field tests are performed based on project design requirements. Accordingly, we have developed the overall investigation plan which enables us to obtain the data needed to define subsurface conditions and perform Engineering analysis and design. 5.1. Boring: Drilling of boreholes was carried out at specified locations to obtain information about the subsoil profile, its nature, strength and also to collect soil samples for strata identification and conducting laboratory tests. The sequence of boring was planned after ascertaining preliminary nature of subsoil profile. Boring is carried out as per the provisions given in IS: 1892-1979. 5.2. Sampling: All the accessories used for sampling and the method of sampling adopted confirms to IS: 2132. All the disturbed and undisturbed samples collected in the field have been classified at the site as per IS : 1498. 5.2.1. Disturbed Sampling (DS): Disturbed soil samples were collected from bore holes at regular intervals to determine the soil type, grain size distribution, Atterberg limits and soil classification. 5.2.2. Undisturbed Sampling (UDS): In each borehole, undisturbed samples are collected at every change of strata. Undisturbed sampler tubes are made up of 100mm diameter, 450mm long MS tubes provided with sampler head with ball check arrangement. Samples are collected in such a manner that the structure of soil and its moisture content do not get altered. At few locations, the sampling tubes could not be pushed into the soil because of hard consistency. The specifications for the accessories used for sampling and the sampling procedure adopted conforms to IS:1892 and IS:2132. Undisturbed samples are used to determine the shear parameters, natural moisture content and unit weight.

4



5.2.3. Transportation and storage of samples: Undisturbed Samples are hand carried holding them in vertical. Shipping and storage was done vertically in most of the situations. Samples are kept as near to ground temperature during shipping. Samples are stored in a dark humid room having 90 94% humidity to prevent loss of moisture. 5.3. Standard Penetration Test (SPT): Standard Penetration Test (SPT) was conducted at different depths in all boreholes. For shallow depths SPT was conducted at close intervals of 1.5m. SPT split spoon sampler of standard dimensions was driven into the soil from borehole bottom using 63.5kg hammer falling from 75cm height. The SPT weight was mechanically lifted to the specified height and allowed to free fall. Blow count for each of three 15cm penetrations was recorded and the N is reported as the blows count for the last 30cm penetration of the sampler leaving the first 15cm penetration as seating drive. When the number of blows exceeded 50 to penetrate the first or second 15cm length of the Sampler, the SPT ‘N’ is regarded as more than 100 as described in IS: 2131 - 1981. SPT refusal is recorded when there is no penetration of the sampler at any stage and also when a rebound of the sounding system is recorded. Samples from the SPT split spoon sampler was preserved in polythene covers and transported to the laboratory. One more polythene cover was provided to prevent the loss of moisture during the transit. The degree of denseness or looseness of natural deposited cohesionless soils can be measured in terms of their relative density. SPT ‘N’ values are correlated with relative density of non - cohesive stratum and with consistency of cohesive stratum. Correlation for Sand/ non-plastic Silt

5

Correlation for Clay/ Plastic soils

Penetration Value (N)

Relative Density

Penetration Value (N)

Consistency

0 - 4 Blows

Very Loose

0 - 2 Blows

Very Soft

4 - 10 Blows

Loose

2 - 4 Blows

Soft

10 - 30 Blows

Medium Dense

4 - 8 Blows

Medium

30 - 50 Blows

Dense

8 - 15 Blows

Stiff

>50 Blows

Very Dense

15 - 30 Blows

Very Stiff

>30 Blows

Hard



5.4. Drilling in rock: For drilling in rock, drilling was advanced by rotary core drilling method using double tube core barrels with T.C bit or diamond bit as per the guidelines of IS:6926-1996. The maximum length of drill run maintained is 1.0m. At the end of each run, the drill rod string with core barrel is extracted from the

from the Borehole and core is recovered

core barrel. The percentage of core recovery is recorded

and the core

pieces are transferred to the core box duly numbered and labeled properly. The selected core samples are sent to the laboratory for conducting tests. The rock core samples are preserved and stored in wooden core boxes as specified in IS:4078 – 1980 Rock classification in terms of weathering, state of fractures and strength is carried out in the following manner. (As per IS: 4464) Term Fresh

Description No visible sign of rock material weathering; perhaps slight discoloration on major discontinuity surfaces

Discoloration indicates weathering of rock material and discontinuity surfaces. All the rock material may be Weathered discolored by weathering. Slightly

Less than half of the rock material is decomposed or Moderately disintegrated to a soil. Fresh or discolored rock is Weathered present either as a continuous framework or as core stones. More than half of the rock material is decomposed or disintegrated to a soil. Fresh or discolored rock is Weathered present either as a discontinuous framework or as core stones Highly

Completely All rock material is decomposed and / or disintegrated to soil. The original mass structure is still largely Weathered intact. Residual Soil

6

All rock material is converted to soil. The mass structure and material fabric are destroyed. There is a large change in volume, but the soil has not been significantly transported.

Grade Interpretation I

CR > 90 %

II

CR between 70% to 90%

III


IV


V

CR between zero to 10%

VI

CR = Zero But N > 50



RELATION BETWEEN RQD AND IN-SITU ROCK QUALITY Rock quality is further measured by frequency of natural joints in rock mass. Rock Quality Designation (RQD) is used to define state of fractures or massiveness of rock. Following table defines the quality of rock mass. RQD CLASSIFICATION

RQD (%)

Excellent

91-100

Good

76-90

Fair

51-75

Poor

25-50

Very Poor

<25

As per IS: 13365 Part -1: 1998 CLASSIFICATION OF ROCK WITH RESPECTIVE OF COMPRESSIVE STRENGTH Rock is also classified by strength of intact rock cores collected during drilling. Rock Compressive strength (UCS) is used to define strength of rock. Following table summarizes classification of rock based on strength. 5.5. Ground Water Level Measurement: The depth of ground water level is supposed to be measured during boring and thereafter the ground water is stabilized as per IS:6935 - 1973. 6. STANDARDS AND GUIDELINES FOR FIELD INVESTIGATIONS: Field exploration by boring was as per below given standards: S. No

7

IS Code No:

Title

1

IS : 1892 - 1979

Code of Practice for sub surface investigation for foundations

2

IS : 1498 - 1970

Classification and Identification of Soils for General Engineering Purpose

3

IS : 2131 - 1981

Method for Standard Penetration Test (SPT) for Soils

4

IS : 2132 - 1986

Code of Practice for Thin- Walled tube sampling of Soils


S. No

IS Code No:


Title

5

IS : 4464 - 1985

Code of practice for presentation of drilling information and core description in foundation investigation

6

IS : 5313 - 1980

Guide for core drilling observations

7

IS : 4078 - 1980

Code of practice for indexing and storage of drill cores

8

IS : 6926 - 1996

Diamond core drilling-Site investigation for river valley projects-code of practice

9

IS : 6935 - 1973

Method of determination of water level in a bore hole

IS: 6065 (part-1) 1985

Recommendations for the preparation of Geological and Geotechnical maps for river valley projects

10

7. GEOTECHNICAL LABORATORY TESTING: Laboratory tests are performed on selected samples in our Geotechnical and Material testing laboratory, Bowenpally, Secunderabad. Laboratory tests comprises of the following tests conducted as per procedures given in relevant IS codes. Following tests are conducted on Undisturbed samples: i)

Sieve Analysis

ii)

Atterberg Limits

iii) Free Swell Index (FSI) iv) Triaxial test (UU) v) NMC & Bulk density vi) Specific Gravity Following tests are conducted on SPT samples: i)

Sieve Analysis

Following tests are conducted on Rock Samples: i)

Water Absorption , Dry density, Porosity and Specific Gravity

ii)

Uniaxial Compressive Strength (UCS)

iii) Point Load Index Test (as per requirement)

8



8. GEOTECHNICAL ASSESSMENT AND FOUNDATION FEASIBILITY By observing the nature of subsurface strata, the type of foundation for a given proposed structure, expected heavy loads on piers and abutment foundations, the following types of foundations can be recommended. a)

Shallow Foundations

b)

Deep/ Pile Foundations

For satisfactory performance of a foundation, the following criteria must be satisfied; I. II.

The foundation must not fail in shear. The foundation should not settle by an amount more than the permissible settle-

ment. The smaller of the bearing pressure values obtained according to above (I) and (II), is adopted as the allowable bearing capacity. 8.1. DEPTH OF FOUNDATION Depth of Analysis: For footing resting on multilayer deposits, weighted average or average of the ‘C’ and ‘Ø’ values upto a depth of ‘H’ = 0.5 B Tan (45 + Ø/2) 8.1.1. FOUNDATION IN SOIL A foundation must have an adequate depth from the considerations of adverse environmental influences. It must also be economically feasible in terms of overall structure. Depth of foundation in soil shall be decided as per Clause 705.2 of IRC 78 for open foundations and confirmed with clause 7 of IS : 1904 for special cases like; where volume change/ scour is expected/ or when foundation is to rest on sloping ground/ made or filled up ground/ frost action is expected etc. Scour depth calculation: Hydrology for the structures is calculated separately and presented whereas, maximum scour depth based on erodible strata has been worked out and presented in summary of borelog results itself. If the strata at which founding level arrived based on scour depth is soil, the founding level has been arrived as explained below (i.e Founding level = H.F.L- 2*d sm - 2 in case of piers and H.F.L – 1.27*d sm - 2 in case of abutments) as per IRC : 78 provisions. 9



Silt Factor: This is important factor for determining the scour depth of erodible strata. It is calculated using following procedure as per IRC:78 (clause 703.2.2) & as suggested in IRC: 5 (clause 110.1.3) Where

Ksf

=

1.76√(dm)

Ksf

=

Silt Factor

dm

=

Mean Diameter in mm

The mean scour depth below Highest Flood Level (HFL) for natural channels flowing over erodible bed can be calculated as per IRC : 78 (clause 703.2)

Where

dsm

=

Db

=

1.34 *(Db 2/ Ksf )1/3 The design discharge for foundation per metre width at effective linear water way

Ksf

= Silt factor for a representative sample of bed material obtained upto the level of anticipated scour

The minimum depth of Open foundation shall be upto the stratum having safe bearing capacity but not less than 2.0m below scour level or protected level as per IRC:78 (Clause 705.2.1) Floor Protection: When high discharges are encountered in a stream water flows turbulently which results in erosion of the bed. To prevent this, floor protection can be suggested for an economic shallow/ open foundation. As per IRC: 78 – 2000, clause 703.3.2, for the design of floor protection works for open foundations, the following values of maximum scour depth may be adopted:

10

I) In a straight reach

:

1.27 dsm

II) In a bend

:

1.50 dsm or on the basis of concentration of flow



8.1.2. FOUNDATION IN ROCK As per clause 705.2.2 (a) of IRC:78; for hard rock with an ultimate crushing Strength of 12.5 MPa or above, the depth of foundation shall be 0.60m below rock surface and 1.50m for all other cases. The embedment of the foundations shall be decided keeping in view the overall characteristics like fissures, bedding plans, cavities, ultimate crushing strength, proposed treatment of foundation strata etc. 9. OPEN/ SHALLOW FOUNDATIONS IN SOIL The safe bearing capacity of soil is the net intensity of loading which the foundation will carry, without undergoing settlement in excess of the permissible value for the structure under consideration. 9.1. Net safe bearing capacity from shear consideration: 9.1.1. For Clay Soils (Φ = 0): The net ultimate bearing capacity immediately after construction on fairly saturated homogeneous cohesive soils shall be calculated using following equation. qd = C Nc Sc dc ic ; Where

Nc = 5.14

The value of ‘C’ shall be obtained from unconfined compressive strength test or static cone penetration test or triaxial shear (UU) test. Alternatively Net ultimate bearing capacity can be determined by using the following equation; qd = C Nc Sc dc ; Where

qd = Net ultimate bearing capacity

A factor of safety of 2.5 is used Considering Φ = 0, Nc = 5.14 Thus the equation is simplified as q

(net safe)

=

1/ 2.5 *C*5.14 Sc dc

=

2.056 C Sc dc

9.1.2. For C - Φ soils: For General shear: Φ ≥ 360 and C ≥ 5 t/m2 qd = C Nc Sc dc ic + q ( Nq-1) Sq dq iq + 0.5 g B Ng Sg dg ig W ' 11



For Local shear: Φ ≤ 280 and C ≤ 3 t/m2 qd = (2/3) c Nc Sc dc ic + q ( Nq-1) Sq dq iq + 0.5 g B Ng Sg dg ig For Intermediate Shear: Average or interpolate between Local and General Shear. 9.1.3. Reduction Factors: Determined Bearing Capacity Factors Nc , Nq, Nγ from Table 1 of IS : 6403-1981 Shape factors Sc Sq Sγ from Table 2 of IS : 6403 - 1981 Depth factors dc dq dγ from clause 5.1.2.2 of IS : 6403 - 1981 Inclination factors ic iq iγ from clause 5.1.2.3 of IS : 6403 – 1981 9.2. Net Safe Bearing Capacity: Net safe bearing capacity is obtained by dividing the above Net Ultimate bearing capacity by the factor of safety of 2.5.

N et S afe Bearing C apacity =

1 × N et ultimate b ea ring cap a city FO S

9.3. Determination of Safe Bearing Capacity (SBC) from SPT 'N' value considerations As there is neither undisturbed sample nor C, Φ values are available, but only N values are available, Net Safe Bearing Capacity has been assessed based on SPT (N) values. Therefore the safe bearing capacity of foundation soil at proposed founding depth based on corrected SPT (N) value is determined using following theories.

12


I) Based on Terzaghi-Peck Theory:

[

q a =3 . 35∗C b∗ N −3 ∗

2

]

B+ 0 . 3 ∗W γ∗d t 2B

where, qa

=

Allowable net increase in soil pressure (t/m 2).

Cb

=

Correction Factor

N

=

Corrected SPT number

B

=

Width of footing (m)

wγ

=

Water table Correction Factor

dt

=

Depth Factor

II) Based on Teng’s Theory:

[

q a =35∗ N − 3∗

2

]

B+ 0 .3 ∗W γ ∗R d 2B

qa

=

Allowable net increase in soil pressure (kN/m2).

N

=


B

=


wγ

=

Water table Correction Factor

Rd

=

Depth Correction Factor

1+

Df B

 2.0

III) Based on Peck’s Theory:

q a = 0 . 41∗C w∗ N ∗ S where, qa

=

Safe settlement Pressure (kN/m2)

Cw

=

Water table Correction Factor =0 . 5

N

=


S

=

Settlement (mm)

13

0 . 5∗D w D f +B




IV) Based on Meyerhof’s Theory:

q a =C b∗

[

]

N ∗S ∗d m .. .. . .. . IfB< 1 . 2 m 20 . 8

q a =C b∗

[

Where qa

=

Allowable net increase in soil pressure (t/m 2).

N

=


B

=


Cb

=

Correction Factor

dm

=1

0 . 3∗ D f ≤1. 33 B

V) Based on Bowle’s Theory:

q a =0 . 73∗ N ∗R D1 ∗S . . .. .. . IfB< 1 . 2 m

[

2

]

B+ 0. 3 q a =0 . 48∗N ∗ R D2∗ ∗S .. . .. .. IfB> 1 . 2 m Where 2B qa

=

Safe Bearing Pressure (kN/m2)

N

=


S

=

Settlement (mm)

RD1

=1 

0 . 2∗D f ≤1 . 20 B

RD2

=1

0 . 3∗ D f ≤1. 33 B

14

]

N ∗S ∗d m .. .. . .. . IfB> 1 . 2m 31. 2



10. PILE FOUNDATIONS The total vertical load carrying capacity of pile foundation is a combination of skin friction resistance along the surface and end bearing resistance at pile tip, when Piles are installed through layered soils. The pile design in soft soils has relatively high skin friction resistance and granular soils have high end bearing resistance. Generally piles resting on sound rock can be loaded to their safe structural capacity. But for the piles resting on weathered rock it is necessary to provide Socketing depth. In the present situation socketing depth has been considered based on IS 14593-1998, Table 1 of Clause 6.5.1 and IRC 78-2009 amendments. The General practice of calculating Ultimate Bearing capacity of pile socketed into the rock is of following categories: a)

Ultimate load capacity calculated from end bearing resistance only.

b)

Ultimate load capacity calculated from skin frictional resistance only.

c)

Ultimate load capacity calculated from combination of both skin friction & end bearing resistance.

d)

Ultimate load capacity calculated from end bearing resistance and ultimate side socket shear in case of piles resting on rock.

IRC: 78– 2009 amendments suggests the following methods for calculation of pile capacities 10.1.

Capacity of Piles in Intermediate Geo-material and Rock:

The ultimate load carrying capacity may be calculated from one of the two approaches given below: Where Cores of the rock can be taken and Unconfined Compressive Strength directly established using standard method of testing, the approach described in Method 1 can be used. In situations where RQD shows highly fragmented strata (which is not classified as granular or clayey soils), the approach described in Method 2 (Cole and Stroud approach) can be used. Also for weak rock like Chalk, mudstone, claystone, shale and other intermediate rocks this method is preferred.

15



Method:1 where

Qu

=

Re + R

Qu

=

Ultimate Capacity of Pile socketed into rock in Newtons

Re

=

Ultimate End Bearing

Raf

=

Ultimate Side Socket Shear

=

An Empirical Co-efficient whose value ranges from 0.3 to

Ksp

af

=Ksp qc df Ab + AsCus

1.2 as per the table given below for the rocks where core recovery is reported and cores tested for Uniaxial Compressive Strength. (CR+RQD)/ 2

Ksp

30%

0.3

100%

1.2

CR

=

Core Recovery in %

RQD

=

Rock Quality Designation in %

For Intermediate values, Ksp shall be linearly interpolated. qc

=

Average Unconfined Compressive strength of Core below base of pile for a depth twice the diameter /least lateral dimension of pile in Mpa.

Ab

=

Cross sectional area of base of Pile

df

=

Depth Factor = 1 + 0.4 Length of Socket/ Diameter of Socket. However, value of df, should not be taken more than 1.2.

As

=

Surface area of Socket

Cus

=

Ultimate Shear strength along socket length = 0.225√qc

For calculation of Socket resistance the same should be restricted to 3 MPa.

16



Method: 2 This method is applicable when cores and /or core testing results are not available or when geo-material is highly fragmented. The shear strength of geo-material is obtained from its correlation with extrapolated SPT values for 300mm of penetration as given in table below. Shear Strength/ Consistency

Moderately Weak

Weak

Very Weak

Approx 'N' Value

300 – 200

200 – 100

100 – 60

Shear Strength/ Cohesion in MPa

3.3 – 1.9

1.9 – 0.7

0.7 – 0.4

Qu

=

Re+R

Cub

=

Average shear strength below base of pile for the depth twice the

af

= Cub Nc Ab+ As.Cus

diameter / least lateral dimension of the pile Cus

=

Ultimate Shear strength along socket length = 0.225√qc

For calculation of Socket resistance the same should be restricted to 3 MPa. L

=

Length of Socket

Nc

=

9

10.2. Ultimate Capacity of Pile in Soils: The Ultimate capacity of Pile socketed into the Rock shall be calculated using following equation.

Q u =Q ep +Q sf

Q u =A p∗( C p∗N c +q∗N q +0 . 5∗D∗γ∗N γ )+(( ∑ K∗P Di *tan δ )∗Asi +α∗C∗As ) Where ,

17

Qu

=

Total Ultimate capacity of pile in Soil

Qe

=

Ultimate End bearing resistance

Qsf

=

Ultimate Skin frictional resistance

Cp

=

Average cohesion at pile tip

Nc

=

Bearing capacity factor as per IS 2911(Part 1)

q

=

Effective over-burden pressure at pile tip


Nq, Nγ =


Bearing Capacity factors depending on angle of internal friction 'Ø'

at toe. 

=

Effective Unit weight of bearing soil layer

D

=

Diameter of the pile.

AP

=

Cross sectional area of base of pile.

K

=

Coefficient of earth pressure

PDi

=

Effective overburden pressure at center of gravity of the pile

δ

=

Angle of wall friction between pile and soil (taken as 2/3 of Ø )

Asi

=

Surface area of the pile stem.



=

Reduction factor as per IS 2911(Part 1)

As

=

Surface area of the pile shaft.

C

=

Average cohesion through out the length of the Pile.

Total Ultimate Safe Capacity of Pile: Total Ultimate Safe capacity of the pile in rock is obtained from above ultimate capacity divided by factor of safety of 3 for end bearing resistance and 6 for side socket shear resistance. Where as In soils the total safe capacity is obtained by dividing the ultimate capacity with a factor of safety of 2.5 for both end bearing resistance and skin friction resistance.

Q s= 10.3.

Re R + af F .S F .S

&

Q s=

Qep Q sf + −W p F.S F.S

Lateral Capacity of Pile

The Long flexible pile, fully or partially embedded, is treated as a cantilever fixed at some depth below the ground level. The Depth of Fixity and hence the Equivalent Length of Cantilever are determined using the plots of Fig: 2 of 2911-Part I-2. Where T = 5√EI/K1 for sands and normally loaded clays; R = 4√EI/K2 for Overconsolidated Clays T, R are the Relative Stiffness Factors K1 and K2 are constants in kg/cm2 given in Table 1 and 2 of 2911-Part I - 2 18



E is the Young's Modulus of the Pile Material in Kg/cm2 I is the Moment of Inertia of the Cross Section in cm4. Fig: 2 of 2911-Part I-2 is valid for Long Flexible Piles where the embedded Length Le is ≥ 4R or 4T. Knowing the Length of Cantilever, the Pile head deflection (Y) shall be computed using the following Equation: Y in cm

=

Q(L1+Lf)3/ 3EI, for free Head Pile

Y in cm

=

Q(L1+Lf)3/ 12EI, for fixed Head Pile

Where L1 is the Free standing length/ Unsupported length of pile Lf is the Depth of fixity

19

Q is the Lateral Load in kg.



11. SUMMARY OF FOUNDATION DETAILS: Foundation Strata

Safe Bearing capacity (t/m2)

Pile capacity (t)

Lateral capacity (t)

12.5 x 8

Stiff to Very Stiff Sandy Clay

15

-

-

289.444

24 x 14.5

Soft Disintegrated ROCK

40

-

-

Raft

261.847

12.5 x 8

Stiff to Very Stiff Sandy Clay

15

-

-

-

Raft

258.868

12 x 5

Highly Weathered Strong Rock

50

-

-

261.857

-

Raft

257.357

12.5 x 12


45

-

-

MIB

258.624

-

Raft

257.222

14.5 x 6


45

-

-

508+583

MIB

257.302

-

Raft

253.91

14.5 x 12

Reddish Hard Clay

35

-

-

507+773

2 Lane VUP

269.640

-

Raft

268.640

14.5 x 12

Medium Dense Clayey Gravel with Sand

35

-

-

S. No.

Existing chainage

Proposed Chainage

Type of Structure

RL of the ground (m)

Scour Level (m)

1

28+750

523+305

Half Trumpet

262.952

-

Raft

261.847

2

36+233

517+060

4 Lane VUP

290.444

-

Raft

3

38+853

514+515

MIB

262.952

-

4

39+810

513+566

MIB

261.967

5

43+607

509+760

MIB

6

43+905

509+462

7

44+830

8

45+789

20

RL of the Foundation Type of foundation size Foundation (m) L* x B* (m)


Foundation Strata


Pile capacity (t)


12 X 5

Moderately Weathered Strong ROCK

50

-

-

14.5 X 10.0

Highly Weathered Very Weak Rock

45

-

-

280.631

12 x 5

Completely Weathered Extremely Weak Rock

45

-

-

Raft

281.659

12.50 X 6.0

Soft Disintegrated Rock

45

-

-

-

Raft

257.312

21 x 12.5


40

-

-

257.362

-

Raft

253.570

36 x 14.5

Dense Silty SAND

40

-

-

258.522

-

Raft

255.030

25 x 12.5


50

-

-

S. No.

Existing chainage

Proposed Chainage

Type of Structure


Scour Level (m)

9

47+126

506+316

MIB

260.200

-

Isolated

259.200

10

49+552

503+860

MIB

267.390

-

Raft

263.959

11

Kelzar Bypass

501+930

2 Lane VUP

281.631

-

Raft

12

Kelzar Bypass

501+093

MIB-2

282.659

-

13

55+052

498+449

MIB

260+191

14

56+979

496+428

MIB

15

58+550

494+892

MIB

21




S. No.

16

Existing chainage

Seloo Bypass

Proposed Chainage

493+270

Type of Structure


Scour Level (m)

MJB – A1

258.955

254.210

Pile

240.955

1.20

MJB – P1

259.050

251.620

Pile

240.050

1.20

MJB – P2*

255.890

251.610

Pile

235.890

1.20

MJB – P3

252.940

250.640

Open

248.440

10 x 5

MJB – A2

258.012

253.230

Pile

246.012

1.20

RL of the Foundation Type of foundation size Foundation Strata Foundation (m) L* x B* (m)

Completely Weathered Very Weak Rock Highly Weathered Rock Highly Weathered Rock Highly Weathered Extremely Weak Rock Moderately Weathered Strong Rock


Pile capacity (t)


-

350

30

-

300

30

-

300

30

55

-

-

-

450

30

12.5 X 6

Stiff Sandy Clay with Gravel

15

-

-

12.5 X 6

Very Stiff Sandy Clay

18

-

-

14.5 x 12

Medium Dense Silty Sand

15**

-

-

246.722

14.5 X 8

Stiff Sandy Clay

12/20**

-

-

240.729

12.5 X 10

Reddish Medium dense Clayey Sand

20

-

-

17

Seloo Bypass

493+132

MIB-2

256.477

-

Raft

255.477

18

Seloo Bypass

492+914

MIB-1

264.267

-

Raft

263.267

19

Seloo Bypass

492+204

2 Lane VUP 265.208

-

Raft

263.708

20

65+961

487+542

MIB

248.545

-

Raft

21

67+122

486+368

MIB

241.729

-

Raft

22



S. No.

22

23

Existing chainage

67+725

Proposed Chainage

485+759



Pile capacity (t)


Moderately Weathered Weak Rock

45

-

-

10 x 5

Highly Weathered Weak Rock

45

-

-

237.733

10 x 5

Slightly Weathered Strong Rock

80

-

-

Open

233.349

10 x 5


100

-

-

234.675

Open

233.175

10 x 5

Slightly Weathered Moderately Strong Rock

60

-

-

238.337

236.337

Open

234.837

10 x 5

Moderately Weathered Rock

50

-

-

MJB – P6

240.231

237.231

Open

235.231

10 x 5

Highly Weathered Rock

45

-

-

MJB – P7

240.895

237.895

Open

235.895

10 x 5


70

-

-

MJB – A2

241.684

238.684

Open

236.684

10 x 5

Highly Weathered Very Weak Rock

45

-

-

Type of Structure


Scour Level (m)

RL of the Foundation Type of foundation size Foundation Strata Foundation (m) L* x B* (m)

MJB – A1

241.868

241.868

Open

236.868

10 x 5

MJB – P1

241.795

241.795

Open

238.295

MJB – P2

240.733

240.733

Open

MJB – P3

236.349

234.849

MJB – P4

236.175

MJB – P5


Foundation Strata


Pile capacity (t)


14.5 x 12

Brownish Medium Dense Sand With Gravelly Clay

40

-

-

285.204

12 x 5

Highly Weathered Moderately Strong ROCK

50

-

-

Open

264.885

10 x 5

Moderately weathered and strong rock

60

-

-

-

Open

265.175

10 x 5


50

-

-

-

Pile

261.275

1.20


-

350

20

-

Open

265.338

10 x 5

Highly weathered rock

50

-

-

-

Pile

261.438

1.20


-

350

20

-

Open

266.306

10 x 5


50

-

-

S. No.

Existing chainage

Proposed Chainage

Type of Structure


Scour Level (m)

23

72+328

477+600

2 Lane VUP

276.811

-

Raft

275.311

24

76+650

474+016

2 Lane VUP

286.204

-

Raft

ROB – A1

266.885

-

Salod 25 realignment

ROB – P1

ROB – P2

ROB – A2

24


267.175

471+516

267.338

268.306



S. No.

Existing chainage

Proposed Chainage

Salod 26 reallignme -nt

468+038

Type of Structure


4 Lane VUP 253.699

Scour Level (m)

-


Raft

252.699

24 X 14.5


Foundation Strata


Pile capacity (t)



40

-

-

Note: CWR=Completely weathered Rock, MWR=Moderately weathered Rock, DSS= Dense Silty Sand, DCG= Dense Clayey Gravel, SSC= Stiff Sandy Clay, VSC= Very Stiff Clay, DCS = Dense Clayey Sand* Along with 0.5 m replacement below foundation level with granular material. Note : All Individual bridge reports along with calculations are enclosed in the Annexure.

12. LIMITATIONS: Recommendations contained in this report are based on our field observations, subsurface exploration, laboratory tests and some assumptions. It is possible that soil conditions could vary between or beyond the points explored. If soil conditions encountered during construction differs from those described herein, concerned person at construction is requested to notify the same immediately in order that a review may be made and any supplementary recommendations be provided.

For aarvee associates architects engineers & consultants pvt. ltd.

25

Geotechnical & Material Testing Laboratory - NHAI

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