Innovative Construction Practice and Quality Control Measure for Earth and Rockfil
Salma Dam Project, Afghanistan – A Case Study
This paper deals the related aspects with new innovative construction practice adapted and quality control measure for Earth and Rockfill dam of Salma comprises with clay core (centre in CoT) Filter F1 & F2 and blast rock mass as shell materials available near the dam site are found suitable and are being used in the main dam. The materials for horizontal filters (mixed filter), fine filters F1 and coarse filters F2 collected from Harirud river are screened in the screen plant and graded for their suitability as per designed criteria are being used in main dam in U/s, D/s dam. Part of Shell materials for the rockfill dam are collected from river bed and part from blasted rock materials from the parent rock mass nearby the dam. The physical properties of shell materials are found suitable. Nearly 17,27,108.59 lakhs cum. of materials (shell-14,47,733.60, clay -1,49,040.38 and filter-1,30,334.61 cu.m.) have been placed in the dam so far. For foundation rock of cut off trench (CoT) area was treated with consolidation grout holes and curtain grout holes at 3m c/c with varied grout pressure from of 1-22 kg/cm2. After the treatment, the post permeability tests were found below 5 lugeons.
The foundation bed after necessary treatment were cleaned and dried by pumping out (dewatering) the seeping water. The rock undulations were trimmed and treated with concrete where feels necessary and clay core was placed at the deepest level by maintaining dry state during placing the clay core materials.The filter materials and RBM/ blast rock mass are being placed as per designed gradation curves specified for the materials and quality is being ensured by conducting laboratory and field tests. Peizometer, inclinometer and earth pressure cell have been installed to monitor for characteristic behaviour of dam foundation /dam body as per designed of project.
R.B.Shivali, Senior Research Officer, CSMRS, New Delhi, on deputation to WAPCOS Ltd. at Salma Dam Project, Afghanistan. A.N.N.Prasad, Project Director, Amar Kumar, General Manager (P), R.K.Gupta, C.M.D. WAPCOS Ltd. at Salma Dam Project, Afghanistan
The project is being implemented and executed by WAPCOS Ldt. (A Govt. of India undertaking) on behalf of MEA Govt. of India. This project is taken under development assistance programme as independent fully funding by the Govt. of India to Islamic Republic of Afghanistan and supported by Govt. of Afghanistan.
It is vital that technical specifications for the materials to be used at design stages are fully in conformity during actual construction. To ensure this, a separate Quality Control unit headed by an officer of the rank of Deputy Chief Engineer and supported by a team of engineers was established. The major functions of Quality Control wing are:
(i). To ensure establishment and compliance of quality assurance plan in association with Engineer in-charge and Design organization.
(ii). To analyse results of quality tests.
(iii). To take remedial measures wherever required to achieve the desired results.
(iv). Documentation and follow up.
To achieve the above purpose, the Quality Control wing was divided in to following divisions.
(1) Lab. & Field quality control division (Dam for Earth and Rockfill).
(2) Lab. & Field quality control division (Spillways/Power House/Switch yard)
Earth and Rockfill Dam
The Rockfill Dam of Salma Dam Project is consisted of five different zones of well designed materials. A typical cross section of Salma rock fill Dam indicating zoning of materials is shown in Fig-1.
(1) -Impervious Core (well graded impervious core material with max. particle size upto 100 mm.)
(2) -Upstream/Downstream Shell materials (well graded material max. size 1000 mm) should not be greater than 5% and Cu Uniformity coefficient should be less than 50 and Cc Coefficient of curvature should be between 1-4
(3) -Fine FilterF-1 (well graded material, max. size less than 20 mm)
(4) -Coarse Filter F-2 (well graded material, max. size less than 80 mm,)
(5) -Riprap (well graded blasted rock, max. size 400-1200 mm. and 900-1200mm should not be greater than 10% and min size should not be less than 10%)
The till date quantities placed for above indicated zones are shown in the Table-1. The borrow areas for these materials were selected based on the extensive geotechnical investigations.
Keeping in view the massive quantities and testing for the proper quality control of all the above materials, the testing/quality checks were divided into two stages:
(i). Quality checks before placement of materials in Dam body
(ii). Quality checks after placement of materials in the Dam body
In accordance with the above following testing/procedures are being followed for different zones of materials.
Impervious Clay Core Material
The borrow area for impervious clay material is located at Salma/Dekhan. The requisite impervious stock piles for core material obtained from Salma/Dekhan borrow area involved to make stockpiles as per required gradation and moisture content. Water was also added in each layer of stockpiles as per requirement to accommodate losses during excavation and transportation in such a way that available moisture content at the time of placement was near to OMC. The test required to be performed along with its frequency are shown in Table-2.
(a). Tests Before Placement:
(i). Gradation Composition and Moisture Content:
The material proposed to be placed was required to be of specific designed gradation falling within the limits of specified curves.
The frequency of testing achieved was 1 in 1500 cum against desired, frequency of 1 in 3000 cum. Samples of test results for designed gradation are shown in Fig.-2 along with the specified gradation limits. Besides gradation moisture content in the stockpile was also checked and it was ensured that moisture content is near to OMC.
(b). Tests after Placement:
(i). Gradation Composition/Layer thickness: As per designer, the thickness of clay was specified to be placed in each layers of 30 cm and compacted by 6 passes of 20 t vibratory compactor to achieve 25 cm.
The layer thickness was controlled by height of filter layers which was laid prior to the placement of clay core material and by marking contours on abutments. The placement test results of gradation composition is shown in Fig.3
(ii). Moisture content: Moisture content of 13% ± 2% was ensured in the impervious clay material before compaction, to achieve the desired compaction and density results.
Total 635 no. of gradation tests were carried out.
(iii). In-situ Dry density: The designed and specified density for impervious clay is 95% of the Proctor density and was greater than 1.71 t/cum for central portion and is 92% of the Proctor density as greater than 1.66 t/cum for contact zone are being maintained. The density for each layer is being determined with monolithic sampling by taking 4-5 samples in each layer. The average of test results from central zone and contact zone are done to arrive at the density of the layer placed. A sample of density determination for the material along with test procedure is given below in Table-3 and the samples collection is shown in photo-1 by core cutter method.
a) In-situ density test by Core Cutter Method
Total 300 (average of 4-5 samples) tests for density was carried out for the clay core material
b) In-situ density test by Sand Replacement method
Total 20 (average of 4-5 samples) tests for density was carried out for the clay core material. Required density was achieved by 95% of dry density as 1.71 t/cum for central zone and 1.66 t/cum for contact zone. For cases where achieved density was less than specified additional compaction was done by applying additional passes of compactor. Normally by applying two additional passes of compactor, the specified density was achieved in such cases also as settlement should not be more than 5 mm for last additional passes. The samples collection is shown in photo-2 by sand replacement method.
(iv). Permeability tests: Permeability tests could not be conducted on the compacted clay core zone due to non availability of equipment. However, a temporary artificial arrangement could be made to conduct the same test and permeability of the order of 10–6 cm/sec. was achieved, indicating specified imperviousness of the material.
Shell Material: The river borrow area for the shell material was brought partly located near u/s and d/s of the dam and partly is being taken from the rock blast materials from d/s rock quarry. The materials from the river borrow area was screened and processed then placed in the Dam body while the rock blast materials placed directly without processing. The test required to be performed along with its frequency are shown in Table-4.
(a). Tests before Placement:
(i). Gradation Composition and Moisture Control: The material to be placed in shell zone of the Dam is designed for specific gradation falling within the limits of specified curves. To facilitate gradation tests, the whole borrow/quarry areas were divided into smaller area units. The samples were taken from these areas to check the gradation of shell material available in the borrow/quarry areas. Any area not giving results as per specification was marked and the material from such an area was not put to use.
Total 40 no. of tests were carried out to check the gradation of shell materials. The sample test results of design gradation for the material used are shown in Fig-4 along with the specified gradation limits. It is seen that granular composition of the material used was within specified gradation limits. Moisture content was also checked along with gradation tests to facilitate calculation of water to be added for proper compaction of the material.
(b).Tests after Placement
(i). Gradation composition/Layer thickness: The shell material was specified for placement in layers of 1000 cm thickness each reduced to 990 cm after compaction by 8 passes of 15 t vibratory compactor. The layer thickness of 1000 cm was controlled by marking contours on the abutments.
Total 120 no. of tests were carried out to check the gradation of shell materials. The sample test results of gradation on compacted layer are tested for the material and are shown in Fig-5 along with the specified gradation limits and sample collection for gradation on compacted layer for shell materials are also shown in photo-3. It is seen that gradation composition of the material used was within specified gradation limits. Moisture content was also checked along with gradation tests to facilitate calculation of water to be added for proper compaction of the material.
(ii). Moisture content: Moisture content of 3–5% was ensured in the shell material to achieve the desired compaction results by adding water 250 lit per cum. to whole placed surface before compaction.
(iii). In Place Dry Density: In Place Dry density of shell material should not be less than 2.0 t/m3 and desirable to 2.14-2.24 t/m3 and was checked by ring and water replacement method. A sample of density determination along with procedures is given in Table-5.
(iv). Field Permeability Test (By Pit Method): More than 40 permeability tests were conducted for determination of percolation of water into shell material. The required permeability was generally achieved more than 1x10-1 cm/sec, after 8 passes of compaction by 15 t vibratory compactor. Working out in-situ Permeability test by pit method on compacted layer for shell materials are shown in photo-4
Fine Filter And Coarse Filter
Fine filter and coarse filter materials were obtained by screening of the river borne terrace material from Harirud river shell borrow area. The material of different sizes obtained from Harirud river borrow area were mixed to make stock piles to achieve the requisite gradation of material. The test required to be performed along with its frequency are shown in Table -6.
a). Tests before Placement
(i). Granular Composition: The material proposed to be placed was required to be of specific gradation falling within the limits of specified curves. Total 20 Nos. of tests were carried out to check the gradation of fine filter and coarse filter materials. The sample test results of the gradation of fine, coarse and mixed (Horizontal) filters used along with specified gradation limits is shown in Fig-6.
b). Tests after Placement
(i). Gradation Composition: The coarse filter & fine filter material was placed in 40 cm. (loose) thick layer each compacted to 35 cm. in thickness by minimum 8 passes of 15t vibratory compactor. Filter material was watered so as to achieve the moisture content of around 5–8%.
Total 30 Nos. of tests were carried out to check the gradation of fine filter and coarse filter materials in CoT areas. The all test results of the gradation are shown in Fig. 7 and Fig. 8. It is seen that materials used conforming to the specified designed gradation limit. The sample collection for gradation on compacted layer for filter materials is shown in photo-5
The coarse filter materials taken as 200 kg of sieve 40mm passing (70-80% of 10mm passing and remaining 20% of 40-10mm) as per conforming the requirements. The Fine filter materials taken as 20 kg of sieve 20mm passing (90% of 10mm passing and remaining 10% of 20-10mm) as per conforming the requirements
(ii). Filter Criteria:
The filter criteria for the Fine filter were conforming the requirements and satisfied by the following;
(iii). In Place Dry Density: In-place density was greater than 1.9 t/m3 for all fine filter, coarse filter and mixed filter (horizontal filter-60% coarse and 40% fine).
The permeability test of filter material after compaction was determined by ring & water replacement method. More than 30 tests were conducted for determination of density and permeability of fine filter and coarse filter material. A sample tested for density and permeability determin- ation along with procedures is given below in Table-7.
(iv). Relative Density
The relative density was achieved 87% or more of field density, after 8 passes of compaction by 15t vibratory compactor.
(v). Sand Equivalent Method
Sand Equivalent for Fine filter F1 was achieved as sand particles 80% or greater than this value.
Sp. Gr. Should be between 2.60-2.65
(vi). Field Permeability Test
More than 30 Permeability tests were conducted for determination of water percolation of filter material. The required permeability for fine filter were achieved as more than 1x10-3 cm/sec and 1x10-2 cm/sec for coarse filter with required density of 2.24 t/cum, after 8 passes of compaction by 15t vibratory compactor, The procedure and working out in-situ Permeability test on compacted layer for filter materials is shown in photo-6 by pit method.
Rip-rap Material
The rip-rap material was obtained from "d/s quarry" situated at a distance of about 2.0 km from the dam site. The material comprised blasted rock fragments, falling within the specified gradation range. Maximum permissible size of blasted rock was 1200 mm. The blasting of rock was done in such a manner so that the blasted material is obtained in required gradation. The test required to be performed along with its frequency are shown in Table-8.
(a) Tests before Placement
(i) Granular Composition: The material to be placed in rip-rap zone of the dam was required to be of specific gradation falling within the limits of gradation envelope.
A Total of more than 4 tests were carried out to check the gradation of rip rap material.
(ii). Tests after Placement: The rip rap material was placed in layer of 1200mm (loose) thickness. The materials should be placed by excavator and dressed and compacted by mason with hand compaction to achieve the desired density of 2.36 t/m3. The photo of riprap placed on the right bank side of the dam is shown in photo- 7
The foundation bed after necessary treatment were cleaned and dried by pumping out (dewatering) the seeping water. The rock undulations were trimmed and treated with concrete where feels necessary and clay core was placed at the deepest level by maintaining dry state during placing the clay core materials.The filter materials and RBM/ blast rock mass are being placed as per designed gradation curves specified for the materials and quality is being ensured by conducting laboratory and field tests. Peizometer, inclinometer and earth pressure cell have been installed to monitor for characteristic behaviour of dam foundation /dam body as per designed of project.
R.B.Shivali, Senior Research Officer, CSMRS, New Delhi, on deputation to WAPCOS Ltd. at Salma Dam Project, Afghanistan. A.N.N.Prasad, Project Director, Amar Kumar, General Manager (P), R.K.Gupta, C.M.D. WAPCOS Ltd. at Salma Dam Project, Afghanistan
Introduction
Salma Dam Project is a glacier and run off the river scheme in West Afghanistan in Western Himalayas, a 107m high earth and rockfill dam located 176 km upstream of Province of Herat on river Harirud. The storage water is to be supplied through the intake vertical shaft (draft shaft) structure of 42 m in depth to carry the water through penstock to generate the power of 42 MW (3 x 14 MW). The Project consists of following major structures.- Rock fill Dam.
- Surface Power House.
- Chute and Shaft Spillways
- Switch yard
The project is being implemented and executed by WAPCOS Ldt. (A Govt. of India undertaking) on behalf of MEA Govt. of India. This project is taken under development assistance programme as independent fully funding by the Govt. of India to Islamic Republic of Afghanistan and supported by Govt. of Afghanistan.
It is vital that technical specifications for the materials to be used at design stages are fully in conformity during actual construction. To ensure this, a separate Quality Control unit headed by an officer of the rank of Deputy Chief Engineer and supported by a team of engineers was established. The major functions of Quality Control wing are:
(i). To ensure establishment and compliance of quality assurance plan in association with Engineer in-charge and Design organization.
(ii). To analyse results of quality tests.
(iii). To take remedial measures wherever required to achieve the desired results.
(iv). Documentation and follow up.
To achieve the above purpose, the Quality Control wing was divided in to following divisions.
(1) Lab. & Field quality control division (Dam for Earth and Rockfill).
(2) Lab. & Field quality control division (Spillways/Power House/Switch yard)
Innovative Construction Practice and Quality Control of Project
The details of Innovative construction practice and quality control checks made during construction for various structures of Project are briefed here under:Earth and Rockfill Dam
The Rockfill Dam of Salma Dam Project is consisted of five different zones of well designed materials. A typical cross section of Salma rock fill Dam indicating zoning of materials is shown in Fig-1.
 |
| Figure 1: Typical Section of Salma Dam |
(1) -Impervious Core (well graded impervious core material with max. particle size upto 100 mm.)
(2) -Upstream/Downstream Shell materials (well graded material max. size 1000 mm) should not be greater than 5% and Cu Uniformity coefficient should be less than 50 and Cc Coefficient of curvature should be between 1-4
(3) -Fine FilterF-1 (well graded material, max. size less than 20 mm)
(4) -Coarse Filter F-2 (well graded material, max. size less than 80 mm,)
(5) -Riprap (well graded blasted rock, max. size 400-1200 mm. and 900-1200mm should not be greater than 10% and min size should not be less than 10%)
| Table-1 | ||
| Sl. No. | Name of material | Quantity ( cum.) |
| 1 | Shell material | 14.47 lac |
| 2 | Clay core material | 1.49 lac |
| 3 | Filter F1 materials | 0.20 lac |
| 4 | Filter F2 materials | 0.37 lac |
| 5 | Mixed Filter materials (40f1:60f2) | 0.74 lac |
| 6 | Rip-Rap material | 0.02 lac |
| Total | 17.29 lac | |
The till date quantities placed for above indicated zones are shown in the Table-1. The borrow areas for these materials were selected based on the extensive geotechnical investigations.
Keeping in view the massive quantities and testing for the proper quality control of all the above materials, the testing/quality checks were divided into two stages:
(i). Quality checks before placement of materials in Dam body
(ii). Quality checks after placement of materials in the Dam body
In accordance with the above following testing/procedures are being followed for different zones of materials.
Impervious Clay Core Material
| Table-2 | ||||||||
Sl. No. |
Materials as per Zone | Before Compaction i.e. inspected in borrow area or in stockpile) | During Compaction | After Compaction of the filled area | Frequency of Complex Lab & Field tests , Alter berg Limit, Shear & Consolidation Characteristics | |||
| Controlling Parameters |
Minimum frequency of soil sample
|
Controlling Parameters | Controlling Parameters | Minimum frequency of soil sample | ||||
| Each layer thickness (maximum) | Minimum no. of passes | |||||||
| 1. | Core Material (Zone-1) | Granular Composition, Moisture Content. | 1 in 3,000 cum. | 30 cm. (Loose) |
6 Passes with vibratory Compaction by 20 Ton roller |
25 cm compacted | 1 in 1000 cum. or Minimum once per Continuous layer of 30 cm (loose) thick |
1 in 1,00, 000 cum. or Minimum once per Season |
| Sp. Gr. | 1 in 1,000 cum. | 2.60-2.75 Av-2.68 |
- | - | Bulk density 1 in 1000cum./4 samples per layer | - | ||
| Grain size distribution | 1 in 1,000 cum | Fines 0.075mm passing should be greater than 20% and coarser upto 100mm | - | - | - | - | ||
| Atterberg's Limit | 1 in 2,000 cum | PI ≥12 | - | - | 1 in 2,000 cum | - | ||
| Natural Water content (3-16%) | 1 in 250 cum | OMC- 13±2 % | - | - | in 100 cum./3 samples per layer | - | ||
| Proctor density | 1 in 5,000 cum | Maximum Dry density-≥1.8 gm/cc | - | 95% of proctor density | 1 in 5,000 cum | - | ||
| Shear Parameters | 1 in 5,000 cum | Ø should be greater than 25-350 and cohesion c-greater than 0.10-0.50 kg/cm2 | - | - | 1 in 10000 cum. | - | ||
| Compression/ Consolidation |
1 in 20,000 cum | - | - | - | 1 in 20000 cum | - | ||
| Permeability | ≤ 1x10-6 cm/sec. | - | ≤1x10-6 cm/sec. | 1 in 10000 cum | - | |||
The borrow area for impervious clay material is located at Salma/Dekhan. The requisite impervious stock piles for core material obtained from Salma/Dekhan borrow area involved to make stockpiles as per required gradation and moisture content. Water was also added in each layer of stockpiles as per requirement to accommodate losses during excavation and transportation in such a way that available moisture content at the time of placement was near to OMC. The test required to be performed along with its frequency are shown in Table-2.
(a). Tests Before Placement:
(i). Gradation Composition and Moisture Content:
The material proposed to be placed was required to be of specific designed gradation falling within the limits of specified curves.
 |
| Figure 2: Gradation results designed for impervious clay core materials with available samples |
The frequency of testing achieved was 1 in 1500 cum against desired, frequency of 1 in 3000 cum. Samples of test results for designed gradation are shown in Fig.-2 along with the specified gradation limits. Besides gradation moisture content in the stockpile was also checked and it was ensured that moisture content is near to OMC.
(b). Tests after Placement:
(i). Gradation Composition/Layer thickness: As per designer, the thickness of clay was specified to be placed in each layers of 30 cm and compacted by 6 passes of 20 t vibratory compactor to achieve 25 cm.
The layer thickness was controlled by height of filter layers which was laid prior to the placement of clay core material and by marking contours on abutments. The placement test results of gradation composition is shown in Fig.3
 |
| Figure 3: Gradation results of impervious clay core materials taken during July-Sept., 2009 |
(ii). Moisture content: Moisture content of 13% ± 2% was ensured in the impervious clay material before compaction, to achieve the desired compaction and density results.
Total 635 no. of gradation tests were carried out.
| Table-3 | ||||
Size of Mould |
Volume of Mould, V (cm³) | Rammer | No of Layers | Blows / layer |
|
Dia 10 cm and ht. 12.75 cm
|
1020.50
|
10 kg for taking sample and 2.6 kg
for carryng test with Std. Proctor density by falling 31 cm height & falling 45cm height of 4.6 kg for modified proctor |
3 5 | 25 25 |
| Moisture content Determination | ||||
1.0 |
Container No. | 47 | ||
| 2.0 |
Mass of container + wet soil (g)
|
39.619 | ||
| 3.0 | Mass of container + dry soil (g) | 36.758 gm | ||
| 4.0 | Mass of water (g), =1-2 | 2.861 | ||
|
5.0
|
Mass container empty (gm) | 14.663 | ||
| 6.0 | Mass dry soil (g) =3-5 | 22.095 | ||
| 7.0 | Moisture content (%) w = (mass of water/mass of dry soil) x100 | 12.95 | ||
| Density Determination by Proctor density | ||||
| 1.0 | From the compacted layer of clay core a sample (with the help of Core Cutter Method) is drawn. The sample is dressed. The sample is weighed and Mass of mould + soil (g) | P+M | 6136.5 gm | |
| 2.0 | Mass of mould (g) | P | 4143 gm | |
| 3.0 | The Mass of compacted soil (M) (g) | (P+M-P) | 1993.5 gm | |
| 4.0 | Mass of compacted soil (M) M Bulk density (r ) (g/cm3) = ---------------------------------------= ---- Volume of Mould (cm³) V |
M ----=r V |
1.95 | |
| 5.0 | Bulk density (r ) (g/cm3) r Dry density (gd) (g/cm3) = ---------------------------------------= -------- (1+ % Moisture content) 1+w% w= moisture content |
r ---- 1+w% |
1.80 | |
(iii). In-situ Dry density: The designed and specified density for impervious clay is 95% of the Proctor density and was greater than 1.71 t/cum for central portion and is 92% of the Proctor density as greater than 1.66 t/cum for contact zone are being maintained. The density for each layer is being determined with monolithic sampling by taking 4-5 samples in each layer. The average of test results from central zone and contact zone are done to arrive at the density of the layer placed. A sample of density determination for the material along with test procedure is given below in Table-3 and the samples collection is shown in photo-1 by core cutter method.
 |
| Photo 1: Sample collection for in-situ density of impervious clay by Core cutter |
a) In-situ density test by Core Cutter Method
Total 300 (average of 4-5 samples) tests for density was carried out for the clay core material
b) In-situ density test by Sand Replacement method
 |
| Photo 2: Sample collection for in-situ density of impervious clay by Sand replacement |
(iv). Permeability tests: Permeability tests could not be conducted on the compacted clay core zone due to non availability of equipment. However, a temporary artificial arrangement could be made to conduct the same test and permeability of the order of 10–6 cm/sec. was achieved, indicating specified imperviousness of the material.
| Table-4 | ||||||||
| Sl. No. |
Materials as per Zone | Before Compaction i.e. inspected in borrow area or in stockpile) | During Compaction | After Compaction of the filled area | Frequency of Complex Lab & Field tests | |||
| Controlling Parameters | Minimum frequency of soil sample | Controlling Parameters | Controlling Parameters | Minimum frequency of shell sample | ||||
| Each layer thickness (maximum) | Minimum no. of passes | |||||||
| 1. | Shell Material ( Zone-3) |
Gradation Composition, Moisture Content. | 1 in 10,000 cum. | 1000 cm. (Loose) |
8 Passes |
Gradation Composition, Dry Density- >Moisture Content |
1 in 10000 cum. or Min. once per Continuous layer of 1180 mm (compacted) thick more than 2.14 t/m3 3% -5 % |
1 in 1,00,000 cum. |
Shell Material: The river borrow area for the shell material was brought partly located near u/s and d/s of the dam and partly is being taken from the rock blast materials from d/s rock quarry. The materials from the river borrow area was screened and processed then placed in the Dam body while the rock blast materials placed directly without processing. The test required to be performed along with its frequency are shown in Table-4.
(a). Tests before Placement:
(i). Gradation Composition and Moisture Control: The material to be placed in shell zone of the Dam is designed for specific gradation falling within the limits of specified curves. To facilitate gradation tests, the whole borrow/quarry areas were divided into smaller area units. The samples were taken from these areas to check the gradation of shell material available in the borrow/quarry areas. Any area not giving results as per specification was marked and the material from such an area was not put to use.
 |
| Figure 4: Gradation results designed for shell materials with available samples |
Total 40 no. of tests were carried out to check the gradation of shell materials. The sample test results of design gradation for the material used are shown in Fig-4 along with the specified gradation limits. It is seen that granular composition of the material used was within specified gradation limits. Moisture content was also checked along with gradation tests to facilitate calculation of water to be added for proper compaction of the material.
(b).Tests after Placement
(i). Gradation composition/Layer thickness: The shell material was specified for placement in layers of 1000 cm thickness each reduced to 990 cm after compaction by 8 passes of 15 t vibratory compactor. The layer thickness of 1000 cm was controlled by marking contours on the abutments.
 |
| Figure 5: Gradation results of shell materials taken during July, 2009 |
Total 120 no. of tests were carried out to check the gradation of shell materials. The sample test results of gradation on compacted layer are tested for the material and are shown in Fig-5 along with the specified gradation limits and sample collection for gradation on compacted layer for shell materials are also shown in photo-3. It is seen that gradation composition of the material used was within specified gradation limits. Moisture content was also checked along with gradation tests to facilitate calculation of water to be added for proper compaction of the material.
(ii). Moisture content: Moisture content of 3–5% was ensured in the shell material to achieve the desired compaction results by adding water 250 lit per cum. to whole placed surface before compaction.
 |
| Photo 3: Sample collection for gradation on compacted layer for shell materials |
(iii). In Place Dry Density: In Place Dry density of shell material should not be less than 2.0 t/m3 and desirable to 2.14-2.24 t/m3 and was checked by ring and water replacement method. A sample of density determination along with procedures is given in Table-5.
| Table – 5 | |||
1.0 |
A M.S. ring of dia 2.0 m is placed on the compacted layer and marked for pitting. | ||
| 2.0 | A polythene sheet is spread over the ring and about 100 to 150 lit water is poured in the ring. Volume of water is noted. | V1 | 50.00 lit. |
| 3.0 | left level of water is recorded with the help of a pointer gauge (by taking three points). | P.R. | 30.15 cm |
| 4.0 | Water and polythene is removed and a pit is excavated inside the ring up to thickness of the layer (upto 1.0 m depth). The excavated materials are screened through 1000mm-10mm sieve. Screened material is weighed by retained individual. | P | 1338.00 kg |
| 5.0 | The material thus excavated is screened through a 10 mm sieve. Screened material is weighed. The 10mm passing materials should not be more than 5% of total and total materials should be around 4 tonnes |
(-10mm) | 265.00 kg |
| 6.0 | 1.0 kg material from (-10mm) material is taken and screened through 4.75 mm sieve. The screened material is weighed. | (- 4.75 mm) Material in 1 kg. | 0.878 kg |
| 7.0 | Aleurite % in the sample is found out = (-10 mm) material x (-4.75 mm) material x 100 = 265 x 0.878 x 100 P 1338.00 |
Aleurite % | 17.39 % |
| 8.0 | A polythene sheet is spread over the excavated pit and water is poured in the pit upto same level as recorded by pointer gauge in step 3 above. Volume of water is noted. | V2 | 580.00 lit |
| 9.0 | Polythene correction factor is determined before computing the bulk density. Polythene correction factor depends on the aleurite %. e.g. Aleu. % Poly. Cor. Factor 17.00 0.9514 18.00 0.9528 hence factor for aleurite 17.39 %, = 0. 9514+0.39 x (0.9528 - 0.9514) |
K | 0.9519 |
| 10.0 | Bulk density is calculated as = K x P (V2-V1) |
Y bulk | 2.403 t/m3 |
| 11.0 | In order to calculate dry density, moisture of material is found out. W1=Weight of wet sample Moisture content = W1-W2 x 100 W2=Weight of dry sample W2 WI-W2=Weight of water Moisture |
MC | 9.89 % |
| 12.0 | Dry density of the sample is calculated as Bulk density/ (1+Aleu.% x Moisture %) = 2.403/(1+17.39x 09.89) 100.00 x 100.00 100.00 x 100.00 |
Y dry | 2.362 t/m3 |
(iv). Field Permeability Test (By Pit Method): More than 40 permeability tests were conducted for determination of percolation of water into shell material. The required permeability was generally achieved more than 1x10-1 cm/sec, after 8 passes of compaction by 15 t vibratory compactor. Working out in-situ Permeability test by pit method on compacted layer for shell materials are shown in photo-4
 |
| Photo 4: Working out in-situ Permeability test on compacted layer for shell materials |
Fine Filter And Coarse Filter
Fine filter and coarse filter materials were obtained by screening of the river borne terrace material from Harirud river shell borrow area. The material of different sizes obtained from Harirud river borrow area were mixed to make stock piles to achieve the requisite gradation of material. The test required to be performed along with its frequency are shown in Table -6.
a). Tests before Placement
| Table-6 | ||||||||
Sl. No. |
Materials as per Zone | Before Compaction i.e. inspected in borrow area or in stockpile) | During Compaction | After Compaction of the filled area | Frequency of Complex Lab & Field tests , Atter berg Limit, Shear & Consolidation Characteristics | |||
| Controlling Parameters | Minimum frequency of soil sample | Controlling Parameters | Controlling Parameters | Minimum frequency of soil sample | ||||
| Each layer thickness (maximum) | Minimum no. of passes | |||||||
| 1. | Filters (Coarse & Fine) | Gradation Composition, Moisture Content. |
1 in 500 cum. | 40 cm. (Loose) |
3 passes for Fine filter & 4 passes for Coarse filter |
Gradation Composition Dry Density Moisture Content Relative density- |
1 in 500 cum. or Minimum once per Continuous layer of 40 cm (loose) thick 1.90 t/m3 5%-8% greater than 87% of field density |
1 in 5000 cum. or Minimum once per every third layer |
(i). Granular Composition: The material proposed to be placed was required to be of specific gradation falling within the limits of specified curves. Total 20 Nos. of tests were carried out to check the gradation of fine filter and coarse filter materials. The sample test results of the gradation of fine, coarse and mixed (Horizontal) filters used along with specified gradation limits is shown in Fig-6.
 |
| Figure 6: Gradation results designed for coarse, fine and Mixed filter materials with available samples |
b). Tests after Placement
(i). Gradation Composition: The coarse filter & fine filter material was placed in 40 cm. (loose) thick layer each compacted to 35 cm. in thickness by minimum 8 passes of 15t vibratory compactor. Filter material was watered so as to achieve the moisture content of around 5–8%.
 |
| Photo 5: Sample collection for gradation on compacted layer for filter materials |
Total 30 Nos. of tests were carried out to check the gradation of fine filter and coarse filter materials in CoT areas. The all test results of the gradation are shown in Fig. 7 and Fig. 8. It is seen that materials used conforming to the specified designed gradation limit. The sample collection for gradation on compacted layer for filter materials is shown in photo-5
 |
| Figure 7: Gradation results of samples of fine filter materials taken during July-Sept, 2009 |
 |
| Figure 8: Gradation results of samples of coarse filter materials taken during July-Sept, 2009 |
The coarse filter materials taken as 200 kg of sieve 40mm passing (70-80% of 10mm passing and remaining 20% of 40-10mm) as per conforming the requirements. The Fine filter materials taken as 20 kg of sieve 20mm passing (90% of 10mm passing and remaining 10% of 20-10mm) as per conforming the requirements
(ii). Filter Criteria:
The filter criteria for the Fine filter were conforming the requirements and satisfied by the following;
(iii). In Place Dry Density: In-place density was greater than 1.9 t/m3 for all fine filter, coarse filter and mixed filter (horizontal filter-60% coarse and 40% fine).
The permeability test of filter material after compaction was determined by ring & water replacement method. More than 30 tests were conducted for determination of density and permeability of fine filter and coarse filter material. A sample tested for density and permeability determin- ation along with procedures is given below in Table-7.
| Table – 7 | |||
1.0 |
A M.S. ring of dia 1.0 m is placed on the compacted layer.ng. | ||
| 2.0 | A polythene sheet is spread over the ring and about 20 to 30 lit. water is poured in the ring. Volume of water is noted. | V | 20.00 lit. |
| 3.0 | Top level of water is recorded with the help of a pointer gauge. | P.R. | 28.06 cm |
| 4.0 | Water and polythene is removed and a pit is excavated inside the ring upto thickness of the layer. Material thus excavated is weighed. | P | 294.00kg |
| 5.0 | A polythene sheet is spread over the excavated pit and water is poured in the pit upto same level as recorded by pointer gauge in step 3 above. Volume of water is noted. | V2 | 154.00 lit |
| 6.0 | Polythene correction factor is taken as 0.98 for density determination of filter materials. | K | 0.98 |
| 7.0 | Bulk density is calculated as = K x P (V2-V1) |
Y bulk | 2.15t/m3 |
| 8.0 | In order to calculate dry density, moisture of material is found out. W1=Weight of wet sample Moisture content = W1-W2 x 100 W2=Weight of dry sample W2 WI-W2=Weight of water Moisture |
W1 W2 W1-W2 MC |
200gm 189.70gm 10.30gm 5.43% |
| 9.0 | Dry density of the sample is calculated as (Bulk density)/ (1+ Moisture %) = 2.15/(1+5.43/100) 100 |
Y dry | 2.039 t/m3 |
| 10.0 | Relative density is calculated as below: RD = Y max x (Y dry - Y min) x 100 Y dry (Y max - Y min) Y max = 2.10 for fine filter & 2.056 for Coarse filter Y min = 1.72 for fine filter & 1.733 for Coarse filter |
RD | 86.46% |
(iv). Relative Density
The relative density was achieved 87% or more of field density, after 8 passes of compaction by 15t vibratory compactor.
(v). Sand Equivalent Method
Sand Equivalent for Fine filter F1 was achieved as sand particles 80% or greater than this value.
Sp. Gr. Should be between 2.60-2.65
(vi). Field Permeability Test
More than 30 Permeability tests were conducted for determination of water percolation of filter material. The required permeability for fine filter were achieved as more than 1x10-3 cm/sec and 1x10-2 cm/sec for coarse filter with required density of 2.24 t/cum, after 8 passes of compaction by 15t vibratory compactor, The procedure and working out in-situ Permeability test on compacted layer for filter materials is shown in photo-6 by pit method.
 |
| Photo 6: Working out in-situ Permeability test on compacted layer for filter materials |
Rip-rap Material
The rip-rap material was obtained from "d/s quarry" situated at a distance of about 2.0 km from the dam site. The material comprised blasted rock fragments, falling within the specified gradation range. Maximum permissible size of blasted rock was 1200 mm. The blasting of rock was done in such a manner so that the blasted material is obtained in required gradation. The test required to be performed along with its frequency are shown in Table-8.
| Table-8 | |||||||
Sl. No. |
Materials as per Zone | Before Compaction i.e. inspected in borrow area or in stockpile) | During Compaction | After Compaction of the filled area | Frequency of Complex Lab & Field tests | ||
| Controlling Parameters | Minimum frequency of soil sample | Controlling Parameters | Controlling Parameters | Minimum frequency of soil sample | |||
| Each layer thickness (maximum) | |||||||
| 1. |
Blasted Rockfill (Zone-5)
|
Granular Composition |
1 in 10,000 Cum.
|
900-1200 mm -should not be more than 10% 400 mm –should not be more than 10% Quality- Rock should be sound and no air cracks Density- not be less than 2.60 t/m3 Sp. Gr.– not be less than 2.60 |
Dry Density | 1 in 100,000 Cum. |
- |
(a) Tests before Placement
(i) Granular Composition: The material to be placed in rip-rap zone of the dam was required to be of specific gradation falling within the limits of gradation envelope.
A Total of more than 4 tests were carried out to check the gradation of rip rap material.
(ii). Tests after Placement: The rip rap material was placed in layer of 1200mm (loose) thickness. The materials should be placed by excavator and dressed and compacted by mason with hand compaction to achieve the desired density of 2.36 t/m3. The photo of riprap placed on the right bank side of the dam is shown in photo- 7
Conclusion
- An essential feature of any testing programme for the design and construction of a compacted clay core, filters and rockfill materials is the development of tests for quarry materials which are naturally or blasted available. The rock quarry blast stones materials and naturally available RBM, clay core materials & filter materials were chosen after geological study and geotechnical study of suitability. This procedure helped to ensure the quantity and quality of materials of the quarry to nearly representative of the production of material as possible.
- To arrive meaningful material property of clay core, filters and rockfill (RBM & blasted rock stones) the laboratory tests are being simulated to field conditions as closely as possible, during construction and stock piling. However, materials constituting oversize particles are required specimens of formidable dimensions and the properties of field materials are on the basis of test results from laboratory tests conducted.
- For construction control, all the basic acceptance criteria during construction, all the procedures and process with parameters related to construction materials like; gradation, compaction, moisture content, dry density and permeability were taken into account to satisfy the requirements as per GTS standard by conducting standard laboratory test as well as field tests.
- Based on the test results, it has been observed that the impervious clay core materials posses good to very good compaction characteristics, Atterberg's limits, Plasticity Index, gradation, moisture content, shear strength parameters, dispersivity (Non dispersive) and permeability.
- The test results revealed that the Coarse and fine filter materials are satisfying the required gradation, in place density, relative density and permeability as per designed criteria.
References
- IS 12169:1987 Criteria for design of small embankment dams
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- Manual No. 1110-1-2908 for Engineering and Design, Rock Foundation by U.S. Army Corps of Engineers, Washington, DC 20314-1000, November 1994.
- Water Resources Commission N.S.W., Grou- ting Manual, 3rd edition, Australia, 1980.
- Field Manual, Foundation Treatment for Rockfill Dams, Journal of the Soil Mechanics and Foundations Division, Proce- edings of the American Society of Civil Engineers, Vol. 98, No. SM10, pp. 995-1016, October 1972.
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- Treatment of High Embankment Dam Foundations, Journal of the Soil Mechanics and Foundations Division, Proceedings of the American Society of Civil Engineers, Vol. 98, No. SM10, pp. 1099-1113, October 1972.
- Engineer Manual No. EM 1110-2-2300, General Design and Construction Considerations for Earth and ‘Rock-Fill Dams by U.S. Army Corps of Engineers, Washington, DC 20314-1000, July, 2004
