【正文】 content shall be tested correspondingly. Construction Period RequirementAccording to general plan of Nyala Water Supply Project, construction of the whole wells shall be pleted within 12 months since project mencement. XXXXXXX 工程有限公司3 Construction Deployment amp。 Procedure Construction Deployment Construction ArrangementAccording to site conditions and construction period requirement, construction arrangement is divided into 2 stages: (1) During the first stage, arrange one drilling machine to construct one control well from both the northern end and the southern end of each well array, so as to check whether water yield of individual well and water quality have reached the requirement of detailed design. Accordingly, it can be deduced whether the total water yield in water field can meet the requirement of designed total water volume. Meanwhile, construction technique can be adjusted properly according to construction conditions. Once control wells have been pleted, they can be taken as water source for production and living. (2) The second stage is allround construction stage. When finish the construction of control wells, arrange another drilling machine, that is altogether 2 drilling machines to carry forward construction from south to north according to designed well location. Site ArrangementTo ensure construction work goes smoothly, construction base including administrative area, living quarters, large material site, material warehouse and others shall be set in water field. Construction Plan Equipment SelectionAccording to designed well depth, well pipe structure and stratum condition, SPC and SPJ drilling machines shall be used for well drilling and BW－600 ／30 sludge pumps shall be equipped for borehole flushing. Individual Completed Well Structure According to detailed design, boreholes and pleted wells shall XXXXXXX 工程有限公司follow the following structure: 0m120m, borehole diameter is Ф500mm, well pipe is Φ325mm。 120m300m, borehole diameter is Φ445mm, well pipe and screen are Φ219mm. Drilling MethodAccording to construction geological condition and well structure requirement, the proposed drilling method shall be: First, finish drilling a borehole with roller bit of Ф445mm。 then, expand the hole of 0m130m to Φ500mm. Highquality slurry of low solid phase shall be used during drilling course as borehole flushing liquid. Well Completion MethodAfter the work of drilling and borehole expansion for individual well, as well as geophysical well logging, well pipe shall be set into the well in one time, then to put into gravel, stop water and consolidate shaft wall. Construction Technology ProcedureConstruction technical procedure shall follow the following steps:Hole site confirmationdrilling machine installationhole drillinglower down protection pipeborehole pletiongeophysical well loggingborehole expansionborehole flushing and slurry changingwell pipe installationflushing and slurry changing inside the pipe—put into gravelstop waterwell cementationwell flushingpumping testwater sampling—acceptancewell closing4 Construction Method Borehole PositioningTo locate specific surface position of proposed wells according to well coordinates measured by Total Station. Drilling Machine InstallationI. Site preparation1）Well field should be in high elevation area to avoid water flushing in XXXXXXX 工程有限公司rainy seasons. In well field, fill the construction area with soil to increase elevation if necessary. 2）Level the site surface for putting drilling machines, pact the foundation where shall support heavy parts of drilling machines. The whole foundation shall be leveled uniformly and weightbearing parts should be kept away from water and slurry dipping. 3）Arrange slurry circulation system reasonably, encircling groove shall be not less than 15m and in the middle to set two sedimentation tanks, the volume of slurry tank should be more than 30m3. II. Equipment installation 1） Install drilling machine and sludge pump steadily and levelly, keep the turnplate level. Drilling pressure indicator should be shockproof and waterproof. Mud manifold should me sealed and pressureresistance. Pressure pipe should be fixed in proper position of the drill tower. 2）Installation of all electric appliances and safety protection facilities should meet relevant safety regulations. All electric appliances should have grounding device.3）Install well the drill tower and its tightening steel wire according to regulations. Electric appliances should be put in waterproof and moistureproof places. Installation of power line, lamps and lanterns should meet relevant safety regulations.4）Qualified lightning arresting devices should be installed on drill towers in accordance to safety regulation. Borehole DrillingI. Drilling tool connectionDrilling tools shall be connected as follows（from bottom to top）Roller bit(reaming bit)＋towerstyle drilling collar＋Ф89mm drilling pipe＋vertical spindleII. Drilling parameterRoller bit drilling: drilling pressure is 70％80％ of the total weight of equipped drilling collars。 when reduce pressure in drilling, it is not less than 45t。 speed: 60100 r／min。 discharge capacity of pump: 600 L／min.Reaming bit drilling: drilling pressure: 23t。 speed: 60100 r／min。 select maximum value of discharge capacity of pump. XXXXXXX 工程有限公司III. Flushing liquor selection Select slurry with high quality and low solid phase as flushing liquor to flush borehole, and protect borehole wall. Slurry shall be mixed and used on site. Mix slurry powder with water, then add CMC and NaOH treating pound to make slurry performance meet using requirement. In the course of drilling, slurry performance shall be controlled within the following scope. Specific gravity: Viscosity: 2023 seco