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1、Sokoto Cement Factory Project of the 17th Bureau, Chinese Railway Construction CompanyConstruction Schemes for Foundation pit Excavation And ReplacementComposed by：Editor：Chief editor：Fifth division of 17th Bureau of CRCC, manager department of the Sokoto Cement Factory Project, Nigeria 23th Novembe
2、r 2104Contents1Introduction1.1Basis for the composition1.2Principles for the composition2.1Location2.2Geographic report2.3Ground water and underground water.3Construction techniques and methods3.1Excavation of the foundation pit3.1.1Gradient of the foundation pit3.1.2The stability of the side slope3
3、.1.3The form of excavation3.1.4Preparation for the excavation3.1.5Construction procedures3.1.6Methods3.2Gravel replacement3.2.1Construction material3.2.2Construction preparation3.2.3Techniques and constructional procedure.3.2.4Methods4Organization of construction and logistic work4.1The managing sys
4、tem for construction organization.4.2Human resources for the construction4.3Logistic work4.4Technical guarantee4.5Quality and techniques standard and regulation4.5.1Quality standard4.5.2Quality monitoring organization4.5.3Raising awareness for the importance of quality and professional skills.4.5.4E
5、stablishing quality management code.4.6Safety techniques measures4.6.1Safety regulations for mechanical construction4.6.2Traffic regulations4.6.3Safety regulations for filling construction.4.7Environment protection measures4.8Construction during the rain season4.8.1Collecting weather data4.8.2Techni
6、cal measures for drainage4.9Technical measures for sand storm4.10Contingency planConstruction Schemes for Foundation pit Excavation And Replacement1 Introduction1.1 Basis for the composition1.1.1 Geographic Report for the SOKOTO 3300T/D Clinker Dry Cement Production Line1.1.2 Drawings submitted by t
7、he Owner1.1.3 Unified Standard for Constructional Quality Acceptance of Building Engineering (GB50300-2001）。1.1.4 Code for Acceptance of Construction Quality of Foundation Engineering（GB50203-2002）。1.1.5 Technical Specification for Ground Treatment of Building（JGJ79-002）。1.1.6 Technical Specificatio
8、n for Safety Operation of Construction Machinery（JGJ33-2001）。1.1.7 Code for Investigation of Geotechnical Engineering（GB50021-2001）。1.1.8 Status of the site and surrounding environment1.1.9 Calculation book for construction engineering1.2 Principles for the composition1.2.1 Significantly understandi
9、ng the Basis for the composition, composing within the frame of the previous contract in the spirit of integrity, subjectivity and technical innovationality.Developing executable, scientific and efficient construction schemes in thorough consideration of the status of the site and other professional
10、 drawings2 .Introduction of the project2.1 LocationThe site on which the project is to be carried out locates in North Cement Factory, Sokoto, Nigeria, adjacent to the original cement production line. The size of the site is 700 meters by 600 meters. With the higher South end and lower North end, th
11、e site consist of three stages:114m, 109m and 105m respectively.2.2 Geographic reportIn accordance with the geographic report provided by the Owner, the excavation involves three different types of soil.Artificial fill layer（Q4ml）（stratum number ）Soft soil that widely spreads around the site. Thickn
12、ess:0.311.5. Layer bottom elevation88.85111.25m。Clinosol（Q4dl）（stratum number）The mix of gravelly soil and cohesive soil of brownish red color. Thickness: 0.2319.0m. Layer bottom elevation82.1109.99m。Cohesive soil（stratum number ）:the soil of light gray or yellow-gray color and good solidity. Medium
13、/low compressibility.Characterized by the hard calcareous core. Thickness: 3.2524.83m，Layer bottom elevation75.2787.99m。2.3 Ground water and underground water.The site is going to use water from underground with the depth of seven meters. Water is accessed to through well. The precipitation amount i
14、s significantly low except in raining season, which lasts from July to September. The drainage facilities are needed for the heavy precipitation. 3 Construction techniques and methods3.1 Excavation of the foundation pitIn consideration of the features of the soil and the geographic report, it was pr
15、imarily concluded that layer-by-layer slope excavationshall be applied for all buildings and structures foundation pits. In case that there are buildings or structures that require support for the side slope, then other design should be made available for the construction of the support.3.1.1 Gradie
16、nt of the foundation pit1) LateriteC=15Kpa =8.4 degree=19.7KN/M2) ShaleC=20Kpa =11.4 degree =26KN/MIt is noted in the design drawingsthat the depth of the deep foundation pit H is no more than 10 meters, which fall into two categories in terms of depth: 0mH5m，5mH10M。Based on the equation on the page
17、 41 of Calculation book for construction engineering, the stable slope angle is calculated to be no more than 73 degrees. The gradient of the grading is set at 1/0.5 on account of the safety coefficient and vehicular disturbance.Specific weight of the soil(kg/m3)Angle of gradient()Internal friction
18、angle of the soil()Cohesive force of the soil(kg/m3)When the soil is in the state of limit equilibrium, the maximum height of the side slope (h) can be calculated through this formula.3.1.2 The stability of the side slopeThe safety coefficient is 1.13 based on the diagram below, which meets the requ
19、irement of the design and regulations. The text above: safety coefficient:1.13(Sweden finite slice method, total stress model )3.1.3 The form of excavationAccording to the design drawing, excavation of the foundation pit should be conducted in two different forms corresponding to different depth H:
20、H5m，5mH10m. The details are presented below. In case that the excavation depth is more than 5 meters, a one-meter-wide platform should be created when the excavation reaches the cushion.3.1.4 Preparation for the excavation1) Technical preparation：a) Elevation benchmark has been introduced to the con
21、struction area on the basis of elevation point given by the construction unit.b) Other preparation work include getting familiar with drawings and geographical status, planting axis-control pile, checking underground pipeline, machineries, completing disclosure work.2) Site preparation：a) Double-che
22、cking original control plants and benchmark, laying out positioning line, setting up perimeter for foundation pit excavation line and side slope line. The excavated laterite should be put in a secure location within the site for the purpose of backfilling. Shale should be dumped into the dumping gro
23、und designated by the Owner.b) Properly preserving the foundation pit, examining the stability of the side slope before excavating, mending partially damaged side slope to ensure the stability.c) Organizing machineries and workforce to enter the site in a timely manner. Three excavators, one wheel l
24、oader and six tippers are to coordinate with the transportation. Excavator, wheel loader and tipper need to be checked before driving to ensure the reliability. All drivers should be properly licensed and all machine operators should observe relevant regulations for machine operating. After the vehi
25、cle is started, panel, light, alarm steering system, brake and other necessary parts should be examined for reliability and sensitivity. Fuel, lubricating oil and hydraulic oil also need to be checked to ensure the quality. Hinging parts, connectors require checking for loosening and hydraulic press
26、ure system and hydraulic transmission system for leakage. Loading people in the grapple and violating driving regulation are strictly forbidden and subject to penalty.d) Construction schemes are open to adjustment brought up by the changing situation on the site or major amendment to the drawing.Sur
27、veying and positioning risk eliminating ground clearing machinery entry excavating mending and maintaining side slope (continuing excavating and maintaining) flattening the foundation base testing proceeding to next stage3.1.5 Construction procedures3.1.6 Methods1) After surveying and positioning, t
28、he excavation lineon the hill crest is to be laid out and excavated by backhoe.2) The excavation work should be conducted layer by layer on both side of the side slope. To ensure the stability of the side slope, all excavated earthwork should be removed out timely. For rectangular or polylateral fou
29、ndation pit, the number of excavator and other vehicles are to be determined by the size and depth of the foundation pit, 3) The elevation demands constant attention. accurate measurement by the dumpy level is required as it is about to reach the design elevation to prevent over-excavating. Standing
30、 within the turning radius of mechanical arm while it is operating is strictly prohibited. The excavating should be carried out in order and the excavated earthwork need to be removed as the excavation goes on.However, poorly protected worker are not allowed to work in the same spot as the machine.
31、Significant illumination facilities should be in place if it is considered necessary to work at night. One specially designated technician should be responsible for conducting excavators and other vehicles. The foundation pit needs to be thoroughly examined by an inspector for general stability stat
32、us and unstable factors such as cracks and sliding. Any factor that might lead to major damage should be immediately reported to the project manager, while in the mean time the construction needs to be suspended for evacuation. 4) The treatment for over-excavating: if foundation pit undergoes distur
33、bance as the result of poor drainage ormechanical reasons, all disturbance should be removed before backfilling pebble, gravel or graded gravel. If the cause of over-excavating is non-geographical factor, backfilling with pebble, gravel or graded gravel and compacting is necessary.5) As the foundati
34、on pit is excavated to the depth where it is close to design elevation, acceptance and bearing capacity test need to be put up. Proceeding to next stage is not allowed until it is accepted. Any disturbance should be avoided after foundation pit is accepted.3.2 Gravel replacement3.2.1 Construction ma
35、terialThe quality of compacted gravel cushion heavily depends on the nature of the construction material therefore it demands very careful selection. As stated by the design paper, the backfill material for the bottom of foundation pit must be graded gravels. Other standards include that the gravel
36、must be properly graded without impurities such as debris of vegetative plants or other garbage. Graded gravels with the diameter of less than 2mm need to be less than 15%, and the largest diameter should not exceed 50mm.3.2.2 Construction preparation1) InspectionItem such as elevation, foundation s
37、oil, side slope working plane, drainage, treatment for weathered rock and reservation for the working plane must be check for the requirement of construction or design. It can only proceed to foundation treatment after accepted by the Owner, Party A and the project manager department.2) rolling on t
38、he natural soilWhen the requirement for backfilling is met, the natural soil needs to be compacted before proceeding to backfilling. To prevent vehicles from disturbing the foundation base and posing damage to the structure of basal soil, smooth-wheel rolling is to be performed by vibro-roller on th
39、e natural soil in the bottom of the foundation pit.3) The mixing of graded gravelGravel of different diameters should be properly mixed in calculated volume in accordance with the Report for Gravel Cushion Gradation submitted by the lab. The mixing vehicles are three excavator and samples need to ta
40、ken for the purpose of testing after mixing. Well-graded gravels should be loaded to tippers and moved to foundation pit.4) Laying plastic filmDuring the laying of plastic film, the top surface of foundation for laying base should be flat to prevent the plastic film being punctured. The plastic film
41、 should be stretched flat and wrinkleless. All ends should be fixed or anchored. Direct exposure to strong sunlight or air is prohibited.3.2.3 Techniques and constructional procedure.The procedure of foundation treatment is presented as below:FailPassRe-mixingFailGraded gravel mixingFlattening grave
42、l cushionVibrating rollingPassTesting each layerAcceptanceTesting compactablityFlattening graded gravelRolling Retesting and laying lines.3.2.4 Methods1) A gravel cushion of 200mm thickness should be laid without vibrating. Enough space should be saved between each unloaded pile. A specially designa
43、ted personnel should be responsible for conducting the unloading to handle the thickness of the material on the ground and prevent from concentration.2) Construction of gravel cushion should be performed on the same elevation level.3) The effect of rolling largely depends on the flatness. The unload
44、ed materials should be flattened by earthmover and graded gravel must be sufficiently mixed before moving to the foundation pit to avoid the concentration of coarse gravel.4) Certain platform should be reserved in case of multi-section construction to perform overlapping compacting.5) The filling sh
45、ould start from the middle and proceed to both sides, from low-lying areas to nonlow-lying areas. Certain gradient and camber need to be reserved to prevent rainwater from concentrating and therefore affecting the quality of the laying of gravel cushion.6) The filling of the foundation pit and compa
46、cting should be completed layer by layer. One layer of filling must pass the examination of density and rate of water before proceeding to the next layer. 7) Material should be loosely flattened without being compacted first. The thickness of each layer should be kept at 50cm, which requires surveyo
47、rs to check.8) For the best compacting, construction joints of each layer should be staggered with the distance of 2 meters without overlapping.9) During the compacting of vibrating roller, the speed and intensity of the rolling should gradually increase and the wheel trail should overlap. The speci
48、fications are as follow: the rolling starts after the thickness and flatness of the filling, gravel gradation and water rate meet the requirement. Smooth wheel-rolling should be performed on the filling for one time and vibrating rolling for six times. Rolling at a excess speed may lead to flawed flatness of the compacted layer. The speed of rolling should be monitored and stay at around 2km/h (or 33m/min). The rolling should be carried out section by section and layer
