Chapter IIIa construct foundation blockthi cong mong khoi EN

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Trường Đại học Giao thông Vận tải Bộ môn Cầu Hầm ARTIFICIAL WORKS F2 GROUP 3: LÊ VĂN SƠN ĐỒNG THỊ BÍCH LOAN Trường Đại học Giao thơng Vận tải Bộ môn Cầu Hầm CHAPTER IIIa – CONSTRUCTION OF THE SPREAD FOOTING ON NATURAL GROUND Trường Đại học Giao thông Vận tải Bộ môn Cầu Hầm MAIN CONTENTS  Construction methods for foundation pit  Bottom foundation treatment  Concreting spread footing  Fill up the foundation pit  Organize spread footing construction Trường Đại học Giao thông Vận tải Bộ môn Cầu Hầm CONSTRUCT FOUNDATION PIT BY BARE EXCAVATION METHOD Construction methods for foundation pit Bottom foundation treatment Concreting spread footing  Ditch with manual-pressed bulldozer :  Scope of application: The foundation is located on steep terrain, especially the foundation The slope does not exceed 30 °, width of machine operation space> 8m, land level I-III, not waterlogged  Use a bulldozer in the direction of cutting the slope to dig up the slope to lower the natural level to the height that allows the pit to continue digging the ceiling, or use the wall against the wooden boards, if the excavation volume is low, excavate manually because it can not gather the machine into this position  Excavated earth to create construction site, waste from the foundation pit can be transported by container and crane § ­ ờngưmặtưđấtưtựưnhiên Fill up the foundation pit Mặtưbằngưđàoưbằngưmáyưủi Organize spread footing construction Hốưmóngưđàoưbằngưthủưcông Trng i hc Giao thụng Vn ti B môn Cầu Hầm CONSTRUCT FOUNDATION PIT BY BARE EXCAVATION METHOD Construction methods for foundation pit  Excavate by inverse bucket excavator :  Scope of application: Land level I-III, for the terrain is relatively flat, or combination of surface leveling and making the road for digging machines with land transporters to the construction site  These points should be considered when designing organizations using excavators  : Bottom foundation treatment Concreting spread footing Fill up the foundation pit Organize spread footing construction  Range of machines: the ability to reach out, pour high, dig to the lowest position  The position of the machine compared to the edge of the foundation pit to ensure the stability of the talus  Digging bucket capacity and productivity of the machine  Movement of the machine so that it can dig all the positions of the foundation  Number of soil trucks and transportation arrangements Trường Đại học Giao thông Vận tải Bộ môn Cầu Hầm CONSTRUCT FOUNDATION PIT WITH STRUCTURE AGAINST THE WALL Construction methods for foundation pit Bottom foundation treatment Concreting spread footing Fill up the foundation pit Organize spread footing construction Trường Đại học Giao thông Vận tải Bộ môn Cầu Hầm CONSTRUCT FOUNDATION PIT IN THE SUBMERGED CONDITION Construction methods for foundation pit  Excavate foundation pit with submerged base rocks:  If the flow is narrow, shallow water: use dams  If the rock surface is exposed on natural ground: use a siege of soil Bottom foundation treatment Concreting spread footing Fill up the foundation pit Organize spread footing construction  If the flow is wide, flooded deeply : use barrels Trường Đại học Giao thông Vận tải Bộ môn Cầu Hầm CONSTRUCT FOUNDATION PIT IN THE SUBMERGED CONDITION Construction methods for foundation pit Bottom fundation treatment Concreting spread footing Fill up the foundation pit Organize spread footing construction  Dry treatment of the excavated ground :  When the groundwater level is higher than the bottom of the foundation, it must be dried before excavation  Often used small wells The suction head is a 60-80cm diameter filter tube, 1.7m long, deep in the floor with erosion control, suction cups connected to the 38-55mm diameter suction pipe, 5-7m long connected to the concentrated water pipes 75-125mm diameter Trường Đại học Giao thông Vận tải Bộ môn Cầu Hầm BOTTOM FOUNDATION TREATMENT Construction methods for foundation pit Bottom foundation treatment  Treating the bottom of the foundation is soil ground:  Requirements: 0.5m bottom of the foundation must be excavated by hand to ensure the original, only take the land, not compensated Handcrafted thin layer 10 ÷ 15cm  Finished excavation should be poured concrete footings If you have to wait for a new concrete pouring time, leave 0.1­÷ 0.2m just before the concrete pouring and nodularize the floor with the foundation  The role of padding layer: Concreting spread footing Fill up the foundation pit Organize spreadfooting construction  Protects the ground below the bottom of the foundation from being damaged by travel and trampling during the preparation of the foundation pouring  Smooth the bottom of the foundation, forming a lining for cleaning reinforcement and water loss of cement It ensures the quality of concrete footings  Composition of the foundation: The lining foundation is lower than the bottom of foundation There are types  :  Crushed sand mixture with a thickness of 15cm compacted if encountered wet clay background Before pouring the cushioning layer, it is necessary to remove the pasty soil layer at the top then spread out and leveling gradually  Mortar low grade concrete 10cm thick This is a very effective method because it is clean, stable should be the bottom plank for pedestals If the platform is reinforced, the foundation must be used Concrete foundation lining directly into the ground just digging and leveling and flapping by hand If the background is permeable, use dry concrete mixture to spread and compact, the concrete will soak and seal Trường Đại học Giao thông Vận tải Bộ môn Cầu Hầm BOTTOM FOUNDATION TREATMENT Construction methods for foundation pit  Treating the bottom of the foundation is rock ground:  Have to dig up the layer of low intensity on the top above the average 0.5m and make the surface flat  Bottom foundation treatment Concreting spread footing Fill up the foundation pit Removing layers of weathered stone with pressure hammer, if small volume can apply small and shielded explosive measures Waste rock is put into containers and crane  After that, burying the anchor against the sliding of the stone: normal hole drilling Φ­42, l = 50cm according to the sieve diagram, distance a = 50cm  Thoroughly clean the borehole with water, ratio : cement mortar filled with boreholes, without air bubbles in the hole  Anchor the Φ­32 bars with 100cm long edges closed into the hole was stuffed mortar close to the bottom  Then, use a cm thick concrete slab all over the bottom of the foundation to create a flat level design of the bottom of the foundation Neo­chèng­tr­ ỵ t Organize spread footing construction Trường Đại học Giao thông Vận tải Bộ môn Cầu Hầm WATER PUMP IN FOUNDATION PIT Construction methods for foundation pit Bottom foundation treatment Concreting spread footing Fill up the foundation pit Organize spread footing construction  Requirements:  The water pump does not allow the bottom soil to soak in water and during the pouring of concrete and when the foundation is fixing not to flood the bottom of the foundation Therefore, it is necessary to regularly pump the water level lower than the bottom of the foundation until the concrete foundation finishes setting (after hours)  Around the bottom of the foundation build ditches to drain, slope along 0.6% leading to one or two pits located at the corner of the hole, the hole is more deep bottom foundation 0.7m The capacitance of the capacitor must be hour to hold the above types of discharge The pump works no less than 10 minutes Around the pits, the wood was used to prevent landslides and gravels or grit gravel pit bottom  Intrusive water sources :  Underground water: Qng = 1,6.q.F F : Infiltration area, m2; q : intensity permeable through 1m2 foundation bottom, m3/h.m2 depending on the type of background, with fine sand  : 0,15÷ 0,25; medium sand : 0,3÷ 0,5; fine sand :1÷  Rain water: Qmưa = m.F h 24 m : reserve factor = 1,5; F : area of the bottom pit m2; h : daily rainfall of the basin  Condensate water : already in the pit because of the pump to clean the bottom foundation : Qtụ Trường Đại học Giao thông Vận tải Bộ môn Cầu Hầm CONCRETING SPREAD FOOTING Construction methods for foundation pit  Requirements:  The foundation is not reinforced, if any, only the bottom to strengthen  It is necessary to erect steel reinforcement at the pier and abutment body before pouring the footings Bottom foundation treatment  Concrete in each floor of the foundation is poured continuously in a batch, if large volume is divided into two main flows are horizontal, each block
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