GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 METHOD STATEMENT OF SURCHARGE FILL 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 SURCHARGE FILL II INSTRUMENTATION III INSTALLATION AND MONITORING PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 I SURCHARGE FILL Material requirements Materials for surcharge fill shall comply with the requirements of specification section “Embankment Construction” Construction requirements Surcharge fill shall be placed to lines and levels shown on the Drawings or as directed by the Engineer The construction requirements shall be in accordance with specification section “Embankment Construction” The surcharge fill shall be placed gradually at the rate indicated on the Drawings The Engineer shall be responsible for determining when consolidation requirements have been met, and will notify the Contractor when the requirements has been met, and the surcharge may be removed Filling and waiting periods The suggested filling period for improving the stability and the estimated waiting periods for the consolidation work are described on the Drawings The of filling has to be controlled to minimise any instability problem The side slope shall not be greater than 1(V):2(H) unless otherwise approved by Engineer The assumed unit weight of the surcharge used in design is 18kN/m3, and the material is assumed to be compacted sand The Engineer’s criterion for acceptance of completion of consolidation is based on the degree of settlement as stated on the Drawings If not otherwise stated on the Drawings, residual settlement (post-construction settlement) for acceptance in 15 year shall be less than: 10 cm near bridge abutment 20 cm near culvert 30cm in fill area other than bridge abutment and culvert zone II INSTRUMENTATION Description The Contractor shall throughout the works supply, install and monitor various types of instruments for monitoring settlement, horizontal deformation, pore water pressure and ground water table in the fill and natural ground The instruments shall be placed as shown on the Drawings or as directed by the Engineer, and shall be maintained by the Contractor during the construction period and up to the end of the Contract PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 The Contractor shall take utmost care to ensure that none of the instrumentation is damaged or disturbed in any way, and kept in good working order as long as they are required For all those instruments, which project through and above the fill suitable barriers at a distance of minimum 0.75 m around each individual instrument or group of instruments shall be installed and warning signs shall be erected Heavy construction equipment shall not be used within 1.0 m distance of projecting instruments Any instrumentation damaged or disturbed by construction operations shall be replaced or repaired at the Contractor’s expense All instruments shall be labelled with their reference number at the location where the readings or measurements are taken The labelling shall be according to a system and method to be agreed with the Engineer Boreholes for instruments shall be drilled by a suitable method to provide a clean and stable hole of the required diameter to the correct depth Boreholes shall be cased as required Boreholes shall be drilled using clean water Drilling mud or polymer additives shall only be used with the approval of the Engineer During drilling, care shall be taken to ensure that a minimum of material is lost from outside the casing Surging of casing shall not be allowed, and flushing of drilling water up the outside of the casing shall be kept to a minimum For any borehole or part thereof that requires grouting during the installation of instruments, the grout shall be poured into the boreholes using a tremie pipe Instrument types and requirements 2.1 Settlement plate Settlement plates shall consist of a base plate 500×500 mm connected to steel extension rods and protection pipes as shown on the Drawings Length of each extension rod shall be exactly 1.0 m The plates shall be installed on the top of the working platform in such a way that the top of the base plate rests horizontally Before placing of any embankment material, the Engineer shall inspect the complete installation and check the initial elevations on PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 top of the base plate and on top of the rod The rod and pipe shall be extended as the embankment construction advances Based on the settlement records, the Contractor shall calculate and record the bottom elevation of the working platform for each settlement plate 2.2 Observation well The observation wells shall consist of 75 mm dia galvanized iron pipe with a perforated section at the end as shown on the Drawings 2.3 Electrical piezometer Electric piezometers shall be supplied from a reputed manufacturer Information on the proposed type and brand shall be submitted together with technical documentation 2.4 Inclinometer Each inclinometer access tube shall be installed in a pre-bored hole to a depth specified on the drawings The type of inclinometer and method of installation shall be approved by the Engineer Inclinometer access tubes shall be ABS plastic self- aligning casing with couplings The four internal key ways shall be oriented at 90 degrees to each other A biaxial inclinometer probe unit, a rechargeable probe unit and a rechargeable portable digital readout unit shall be used The probe shall be waterproof and corrosion proof, and shall incorporate two force-balanced servo-accelerometers housed in a stainless steel case The body of the inclinometer probe shall be provided with two pairs of spring loaded stainless steel wheels Measurement range shall be ± 30 degrees from the vertical PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 2.5 Grouting For all instruments placed in bore holes where grouting is required, the grout shall be a bentonite - cement mixture, containing sufficient water to achieve a pumpable mix The proportions of the mix shall be such as to conform as closely as possible to the strength or consistency of the natural soils present Trials shall be conducted with different mixes of bentonite and cement (ratio by weight from 4:1 to 8:1) to ascertain the relationship with strength Specimens shall first be cured and stored, and then tested in unconfined compression at intervals of day, days, days and 14 days Three specimens shall be tested on each occasion On the basis of the trials, the bentonite/cement ratio shall be decided The sources of bentonite and cement shall be the same as those used to be used for installation For instruments being removed during or after the works the hole in the ground shall immediately be sealed by bentonite/cement grout for the full depth The grouting procedure shall be approved by the Engineer 2.6 Stabilizing electronic readout devices All electronic readout devices and transducers shall be shaded from direct sunlight during use Probes that are used inside access tubes shall be placed inside the tube and allowed to come to a stable temperature for at least 10 minutes before use Zero or starting values shall only be taken once the temperature stabilization is complete III INSTALLATION AND MONITORING Installation records Installation records of each instrument shall be prepared containing the following information as appropriate for each instrument type: Existing ground level at the time of installation Weather conditions Lengths, width, diameters, orientation, and depth Plant and equipment used, and diameter and depth of any drill casing used Readings required during installation to ensure that all previous steps have been followed correctly, including acceptance tests PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 Simplified log of ground conditions (in drill holes) Type of backfill used Problems encountered, delays, unusual features of installation, and any events that may have a bearing on instrument behaviour A record of commissioning information and readings Instrument installation report The Contractor shall prepare and submit to the Engineer an Instrument Installation Report, which shall incorporate the installation records for all individual instruments and shall include but not be limited to the following information: Text describing the work carried out and the types of instruments installed All installation record sheets Plan and cross-section drawings at a scale of 1:200 showing the locations, elevations and details of all instruments Values of all base readings taken together with any subsequent readings till the time of commissioning Monitoring reports The Contractor shall submit a monitoring report at the end of each calendar month A proposal for the format of the report shall be submitted to the Engineer (including all graphical presentations) for approval at least two weeks before the submission of the first monthly report Each monthly report shall include but not be limited to: A description of monitoring works performed during the previous month Information on reading anomalies or corrections, and factors which may have influenced the measured data Observations and remarks Drawings showing installed locations of instruments (taken from installation report) Data tabulations or plots of instrument readings as described hereafter The Contractor shall have suitable software for generation of the required plots and tabulations The zero time and time axis to be used in all the plots and tabulations shall be agreed with the Engineer The time axis shall be marked in days from “day zero” and an indication of date or month shall be included in the axis The plots and tabulations presented each month shall include all previous readings All plots, where time forms the horizontal axis shall have same scale for the time axis The development of piezometric pressure (vacuum) in the PVD and settlement records PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 shall always be plotted against fill thickness (fill and PVD installation history) The plot for ground water table shall also include rainfall records Where the above measurements have been done in the same location, all these plots shall be combined on the same sheet, where possible Final layouts, scales and details for the presentations shall be agreed with the Engineer at the time of submitting the format PHUONG THANH TRANCONSIN ... CONTENTS I SURCHARGE FILL II INSTRUMENTATION III INSTALLATION AND MONITORING PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 I SURCHARGE. .. Material requirements Materials for surcharge fill shall comply with the requirements of specification section “Embankment Construction” Construction requirements Surcharge fill shall be placed to... construction requirements shall be in accordance with specification section “Embankment Construction” The surcharge fill shall be placed gradually at the rate indicated on the Drawings The Engineer shall