METHOD STATEMENT GMS Ben Luc Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 DEEP MIXING METHOD (SOIL CEMENT COLUMN) AND SAND CEMENT STABILIZED MAT TABLE OF CONTENTS I DEEP[.]
GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 DEEP MIXING METHOD (SOIL CEMENT COLUMN) AND SAND CEMENT STABILIZED MAT PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 TABLE OF CONTENTS I DEEP MIXING METHOD (SOIL CEMENT COLUMN) II SAND CEMENT STABILIZED MAT PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 I DEEP MIXING METHOD (SOIL CEMENT COLUMN) Scope of works Deep mixing or the soil cement column method is the process of improving properties of existing soils, which are essentially soft clay, by mixing stabilizing material: cement with existing soil Soil cement columns can be installed by mechanical mixing method by means of wet mixing (slurry type) The mixing of stabilizing material to the existing soils at various levels shall create soil columns with a predetermined strength, depth and diameter Ground improvement includes constructing deep soil mixing columns, disposing/delivering, transporting and treating the entire disposal soil, creating block and compressing soil, monitoring the settling part of soil Prior to ground improvement, the Contractor is required to receive a written approval by the Engineer regarding equipment and materials to be used and implementation methods for the work References and standards Based on technical specifications – Package A5 TCXDVN 385: 2006 “Stabilization of Soft Soil by the Soil Cement Column Method” Requirements of materials Stabilizing material shall be cement at the quantities given in the table below: Stabilizing material Quantity per cubic meter of existing soil (kg/m3) Cement 180 to 250 Cement shall material Cement in accordance with TCVN 5439-2004 The material shall be stored in containers to prevent damage from moisture before application Water shall be in accordance with the requirements for water for concrete as specified in section - Concrete and Concrete Structure Design of pilot mix The contractor shall perform soil investigation and trial mix tests to determine the soil profile and he appropriate cement content for the soil cement column in accordance with requirements stated in the following sections At a ratio of two (2%) of cement soil columns improved by deep mixing method, a set of undisturbed soil samples shall be collected at depths of 3, 6, 9, 12, 15m and 18m through rotary wash boring, and the following laboratory test shall be performed on each sample - Determination of natural moisture content, unit weight, Atterberg limits and sieve analysis for all samples PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 - Unconfined compression test on all samples For the soil collected from depths of 3, 6, 9, 12, 15 and 18m, trial mixes shall be prepared to determine the unconfined compressive strength and modulus of the mixture of existing clay with cement through unconfined compression test The test shall be performed with at least 15 samples for each mixture proportion as given in the table below Unconfined compression tests shall be made when the test samples are cured at days, 14 days and 28 days At least three samples shall be tested for each different curing time If volume of sample soil is insufficient to conduct the above trial mix, additional borehole shall be installed nearby area Materials Cement Quantities (kg/m3 of existing soil) 180 220 250 The water cement ratio (W/C) shall range between 0,8 and 1,0 the contractor, based on the results from the trials, shall determine a ratio that with be subject to the Engineer’s approval The design unconfined compressive strength from unconfined compression test at 28 days (Qd) shall be as shown on the Drawings - Qd; Design Compressive Strength at 28 days = as shown on the Drawings - Qf; Minimum Field Compressive Strength at 28 days = Qd - Qu, lab; Minimum Laboratory Compressive Strength at 28 days (trial mix target strength to determine a mix proportion) = x Qf However, the actual quantity of stabilizing material to be used in the field shall not be less than minimum values shown in the table above Unconfined compression test shall be made in accordance with ASTM D 2166-85 The test sample shall have minimum diameter of 50 mm and a height of times the diameter The casing shall be the type that can be removed without disturbing of the sample The sample shall be cured by covering with plastic sheet to prevent dehydration of water In the mixture test, the stabilizing material shall be of the same type and characteristics as to be used in the field as shown below: Field Soil Cement Column Mixture Test Wet Mixing Mix stabilizing material slurry of same water proportion to be used in the field with existing clay The report shall describe the mixing method, storage and curing procedure and the test results The report shall also include: Tables summarizing unconfined compressive strength, modulus and unit weight of mixed samples at different curing times PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 Graph showing unconfined compressive strength of mixture against quantity of stabilizing material and graph showing unconfined compressive strength against curing time Technology line Based on geological conditions, the route nature of the work, the Contractor shall select foundation treatment solutions by combination between mechanical and manpower construction of wet and deep mixing technology, ensuring schedule, quality and the highest effectiveness of the work # # # # # # # # # # # # # # # # # # # # # # # # # # # H?, gi?ng, Lake, well, # # # # # # # # # # # # # # # Layout of construction machinery for cement deep mixing construction The construction technique of soil cement piles (or soil cement column, soil cement pier) is done by drilling, deep mixing, in wet state Use driller and dedicated equipment (drilling rod, drilling augers, etc.) to drill into soil with drilling diameter and depth in accordance with technical design During drilling process, soil is not taken out of drilling hole, but its structure is broken on spot The soil is crushed by wings of auger, equally mixed with cement binder by jet pumping equipment into the soil (by air compressed pressure for dry compound or high-pressure pumping mortar for wet binder) PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 Based on the actual situation on site, the contractor will arrange for one machine pilot column construction at locations designated by Engineers Pilot column construction with different cement content in accordance with the design requirements were introduced After receiving the test results, and Engineer approved construction on a large-scale, the contractor will also arrange 03 machines for large scale construction and other ancillary equipment Pilot soil cement column After obtaining appropriate content of cement from testing results, before constructing soil cement columns, the Contractor shall construct a set of three preliminary test columns (trial columns are non-working piles) for verification Tow test columns shall have a diameter of 0,7m and a depth of 20m and one test column shall have a diameter of 0,7 m and a depth of 10m to demonstrate ability of machines, tools and equipment Location of pilot soil cement columns are instructed by the Engineer Any pile which fails the above test shall be replaced by one or more piles by the Contractor or as directed by the Engineer and an additional test shall be conducted for the replaced pile If, in the opinion of the Engineer, it is impractical or inadvisable to install substitute piles in place of a failed pile, the Contractor shall submit proposals to rectify the defect The proposal is subject to the acceptance of the Engineer Construction sequence of pilot cement deep mixing: - Determine the position of the column - Drilling and grouting slurry to design elevation: During the penetration, the mixing blades are rotating to desegregate and disturb the soil to reduce the strength of the ground so as to make the mixing tools penetrate by their selfweight The binder slurry is injected during penetration and mixed with the disaggregated soil When the blade reaches the elevation at the bottom of column, stop but mixing blade is still rotated at least minutes, ensuring the bottom of the pile was mixed thoroughly and uniformly After that, reverse rotation drill and withdraw (spray and cover with cement) to elevation at the top of column The process of drilling and injection of cement slurry to be an operational cycle to make sure soil and cement grout mixed together and the full amount cement slurry - After the completion of cement deep mixing installation until required depth, move to the next Experiment on pilot cement deep mixing column: - Unconfined compressive strength on cored samples from one column - Verification of column dimensions and uniformity of column by pulling-out an entire test column (preliminary test column of 10m length) from the ground PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 The column shall be inspected for size, shape and uniformity of the stabilization along the entire length of the column The Contactor shall submit the pulling method to the Engineer for approval before operation - Pile static load test on test column (preliminary test column of 20m length) using tension pile or ground anchorage system - Unconfined compression test - The unconfined compressive strengths of column at various levels including diameter and depth of column must be determined However, in case that the test for unconfined compressive strengths cannot be satisfactorily attained, pile load test may be required to determine the capacity of column The pile load test of column shall be conducted at 28 days of curing time Unconfined compressive strength of column by the cored sample on site shall be made a interval not more than 1m with age of 28 days old having a value of no less than Qd If the requirements are not met, Judgment shall be made by the Engineer Drilling and sampling experiments: Drilling and sampling along the column to determine the unconfined compressive strength of time days, 14 days and 28 days old Reserve the fourth cylinder and test at 56 days if the 28 day result does not meet the required strength Drilling method: Using drilling equipment with a diameter of sampling tube D75mm The drill samples were then preserved original conditions and the moisture must be preserved until the experiment in the maintenance closet specialized in the laboratory The nominal diameter of the drill samples obtained is 75mm, height of samples is twice the a diameter of the sample Sample surface before the experiment to be flattened by a thin plaster layer Work for samples drilling: During the drilling process, experiments point to make sure implementation within the column section After taking core drilling is completed, the Contractor shall fill the drilled holes with cement slurry Verification of column dimensions Verification of column dimensions shall be made as specified herein Column dimensions can be checked by exposing atop 2m portion of completed column improved by deep mixing method The column shall submit the proposed method on the exposure of column top for inspection to the Engineer for approval before operation PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 - Pile load test on column Pile load test shall be performed in according to ASTM D 1143-81on a soil cement column of age over 28 days applying 1.5 times of deign working load shown in the drawing The pile top shall be properly prepared for the test The method of testing shall be approved by the engineer prior to execution of the work Pile load test shall be performed with capacity of not less than 31 ton for 0.70m diameter cement column when the maximum settlement at pile head shall be less than 10% of column diameter Construction method of large scale construction Construction steps - Step1: Positioning center point of piles Positions of pile’s center points are determined by the approved design drawing To identify pile’s center points, use a total station to get intersection of two theodolites Prior to identifying pile’s center points on site, location of coordinates have to be identified on paper After identifying, other measures are applied to check again to avoid errors Prior to starting drilling work, each pile’s center point is referred to locations A, A1, B, B1 as shown in the chart and marked by four steel sticks The purpose of applying these reference points is to pinpoint center points of the piles when lowering drilling auger These points have to be protected and maintained until lowering and checking stability of drilling auger Center point + Determine the location of column - During constructing drilling piles, regularly check parameters of geometric dimensions and other technical specifications Step 2: Start to drill into soil down to the design depth, with speed of 0.5 – 1.0m/minute and loose the soil in the column, pier PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 - Step 3: - Drilling and grouting slurry to design elevation: During the penetration, the mixing blades are rotating to disaggregate and disturb the soil to reduce the strength of the ground so as to make the mixing tools penetrate by their self-weight The binder slurry is injected during penetration and mixed with the disaggregated soil When touching the required depth, stop but mixing blade is still rotated at least minutes, ensuring the bottom of the pile was mixed thoroughly and uniformly After that, turn drilling auger backwards and take out drilling rod then pump mortar in Taking out drilling rod needs to be combined with mixing and compacting mortar inside the pile thanks to structure of drilling auger Speed to take out drilling auger tb: 0.5m-1.0m/minute The process of drilling and injection of cement slurry to be an operational cycle to make sure soil and cement grout mixed together and the full amount cement slurry Finishing: After taking out drilling auger from the drill hole, 01 mortar column is finished, stop all jet pumping equipment Start cleaning up mortar scattering around the drilling hole and move driller to the new location of the pile PHUONG THANH TRANCONSIN PHUONG THANH TRANCONSIN Cycle Description Section view Items Move Penetration and Installation Penetrate Mixing blade in specified speed with nomal rotation, and soil revomed to the ground surface The binder slurry is injected during penetration and mixed with the disaggregated soil Ðáy c?c/ Bottom of Column Set Mixing blade up to the exact position and confirm the vertical stability Setting-up Penetrate Mixing blade until required bottom level of column,keeping specified speed at least minutes, ensuring the bottom of the pile was mixed thoroughly and uniformly The binder slurry is continuous to injected and mixed with the disaggregated soil Complete penetration Completeion of Installation After the completion of Cement Deep Mixing installtion until required depth, move to the next Withdraw and Installation of CDM column After completion of Bottom treatment, pull Mixing blade out with specified speed and direction of rotation of the blade The additional requested quantity of Cement slurry from the nozzle at the top of blade Withdrawal injection Cement slurry PROCESS OF CEMENT DEEP MIXING PIPE CONSTRUCTION GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 10 GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 Frequency of testing The number of column to be tested shall be as follows: - Take wet-grab samples of the soil / binder mixture at the rate of at least one sample for each 600m3 of soil / binder production with a minimum of one sample per day Each sample shall be of sufficient size to produce four (4) specimens for testing The specimens shall be cylindrical with a nominal diameter of 75mm and length 150mm Test one cylinder for unconfined compressive strength at days, one at 14 days, and one at 28 days Reserve the fourth cylinder and test at 56 days if the 28 day result does not meet the required strength Determine unit weight on each cylinder as part of the unconfined compressive strength testing process - Frequency of coring for determination of unconfined compressive strength shall be performed at a ratio of two (2)% of total number of column improved by deep mixing method - Frequency of verification of column size and uniformity of column by pulling – out test shall be conducted one preliminary test column (non-working column prior to the commencement of working columns) - Frequency of verification of column size at a top 2m portion shall be conducted at a ration of one (1)% of total number of column improved by deep mixing method If the Contractor changes a path of his construction method, additional test shall be conducted - Frequency of pile static load test shall be as stated on the Drawings or as directed by the Engineer - Preliminary test column shall be constructed to the same diameter and length, nd with the same equipment as to be for the working piles Allowable deviation The Contractor shall construct each column to the depth, spacing, vertical alignment, location and with unconfined compressive strength as specified in the Drawing and the Specification In such case that and column constructed with smaller diameter or specified strength, the Engineer shall have the right to order construction of additional column or reconstruct the defective column at the expense of the Contractor Allowable deviation shall be as follows: - Vertical Deviation of column shall not be more than 1% - Position of each column and spacing between column shall not be deviated more than 100 mm in any direction - Diameter column shall not be less than 95% of specified diameter Unconfined compressive strength shall not be less than Qd kPa PHUONG THANH TRANCONSIN 11 GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 II SAND CEMENT STABILIZED MAT This work shall consist of a stabilized mat composed of soil mixed with Portland cement and water, constructed in multi-layers on a prepared and accepted subgrade in accordance with these Specifications and the lines, levels, grades, dimensions and cross sections shown on the Drawings and subject to approval by the Engineer Materials 1.1 Soil Soil shall be sand with a fines content of less than 25% The soil shall be free from contamination by topsoil, vegetation and other organic matter, and any deleterious materials Salt and gypsum content shall be less than 2% Organic content shall be less than 2% 1.2 Cement Cement shall conform to the requirements for Cement in accordance with TCVN 5439-1991 The materials shall be stored in containers to prevent damage from moisture before application 1.3 Water Water shall be clear and free from harmful matter, and shall conform to TCXDVN302-2004 Any indication of unsoundness, marked change in time of setting or a reduction of more than 10% in strength of mortar mixtures made with distilled water shall be cause for rejection Construction method 2.1 Mix design The Contractors submit to the Engineer for his approval samples of materials to be used in the Mat together with the Contractor’s Proposed mix design The Proportion of cement and moisture content required with be determined by means of cylinders tests but in the cement content shall not be less than 3% by dry weight Cylinders tests with be carried out in accordance with AASHTO test method T134 for cement stabilized mixes subject to modification to use he compaction effort defined in AASHTO test method T180 The mix will be so selected that the strength shall be at least equal o the design strength as indicated in this specification section or as shown on the Drawings The design compressive strength (Qd) of the cement stabilized mat shall be an unconfined compressive strength of not less than 0.2Mpa at 28 days of curing tested in accordance with AASHTO test method T208 - Qd; Design Compressive strength at 28 days = 0.2Mpa - Qf: Minimum Field Compressive Strength at 28 days = 0.2Mpa - Qu, lab, Minimum Laboratory Compressive Strength at 28 days (trial mix PHUONG THANH TRANCONSIN 12 GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 target strength to determine a mix proportion) = 0.6Mpa (3 times of Qd and Qf) 2.2 Equipment Equipment shall be suitable for the work specified, consist of motor graders, water tankers, pneumatic rollers, vibrating rollers or steel wheel rollers together with dump trucks and shall have met with the approval of the Engineer as to type, capacity, design and manufacture before construction ts permitted The equipment shall be capable of constructing the mat to meet the requirements specified and to permit the measurements required 2.3 Initial testing The contractor shall make and test trial mixes using different proportions of stabilizer and with select mix proportions that give strengths of test cylinders made and cured in the laboratory of not less than 105% of the required strength, This mix will be the Approved Mix for use in the Works However, regardless of the above requirement, the cement content for cement stabilized mixes will be not less than 3% 2.4 Mix control The entire operation of mixing and compaction of cement stabilized mat shall be subject to close control and frequent testing will be required as the work proceeds to ensure that the strength and density requirements are being maintained To evaluate the quality of the mix the Contractor shall collect at least samples at every 100 m of cement stabilized road section or 2.500 m2 of stabilized area whichever lesser, placed in the Works for conducting unconfined compression tests The test results shall not be less than the required design strength of 0,2Mpa The Contractor shall provide to the Engineer samples of soil for stabilizing at least 10 days in advance of its use so that any necessary adjustments to the mix design may be made and approved Failure to so will make the Contractor responsible for replacing at his own expense any sections of work that are unsatisfactory on account of an unsuitable mix 2.5 Mixing Only mixing by a central plant mix method shall be used The materials shall by dry mixed before addition of water so that cement balls are not formed when water is added The water content shall be within two percentage points of the optimum moisture content for the compaction required Placing and mixing shall be completed and compaction started within 30 minutes of the addition of water in the case of cement stabilized mixes The soil cement shall be placed in uncompacted layers not exceeding 25 centimetres subject to the approval of the Engineer PHUONG THANH TRANCONSIN 13 GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 The contractor shall give the Engineer every facility for checking the actual quantities of cement used in the construction and in the case of central plant mix shall provide equipment such that the Engineer can check the proportions by calibration tests 2.6 Spreading and compaction A trial section with minimum 50m length shall be constructed fist to demonstrate the correct function of the mixing plant, and the spreading and compaction equipment Mixed material shall be placed, leveled and compacted Adjoining section of previously completed mat shall be neat, clean and treated at the interface with slurry of cement, sand and water Construction joints shall be trimmed to be vertical before adjoining sections are constructed The layer shall be compacted throughout its depth to 95% of the maximum dry density obtained from the test method used in mix design Compaction shall be uniform over the whole area and shall be done in such a way that not ruts are formed The use of both steel tired rollers and pneumatic tired roller will be required Compaction shall be completed to the required standard within hours of mixing for cement stabilized mixes 2.7 Protection The mat shall be protected as necessary to maintain the surface within the tolerances specified and to prevent failure from traffic or other causes 2.8 Acceptance After final compaction, test cores shall be taken from the mat to determine the thickness at intervals not greater than 100m Any part of the mat which fail to meet the Specifications or which originally having met the Specifications subsequently suffers damage or deformation shall be rebuilt to the Specifications to the full depth of the mat at the Contractor’s expense Coring with unconfined compressive strength testing to ASTM D2166-06 shall be carried out as basis for field strength check, at intervals not greater than 100m PHUONG THANH TRANCONSIN 14 ... existing soil (kg/m3) Cement 180 to 250 Cement shall material Cement in accordance with TCVN 543 9-20 04 The material shall be stored in containers to prevent damage from moisture before application... Expressway Project Package A5 Civil Works Km 32 +45 0 to Km 35+900 - Pile load test on column Pile load test shall be performed in according to ASTM D 1 143 -81on a soil cement column of age over 28... Thanh Expressway Project Package A5 Civil Works Km 32 +45 0 to Km 35+900 10 GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32 +45 0 to Km 35+900 Frequency of testing The number