CN101215834A - Construction Method of Outrigger Type Diaphragm Wall - Google Patents

Abstract

A construction method for an outrigger type underground diaphragm wall belongs to the technical field of building construction technology. The construction process is as follows: determine the control points of each axis; guide wall construction; mud preparation tank wall and use mud to protect the tank wall to ensure the stability of the tank wall; slot construction; outrigger construction; underground wall steel cage production and processing; outrigger steel cage production , align and connect with the reinforcement cage of the underground wall; press and release the reinforcement cage; select the joint; press and release the joint and pour the underwater concrete pipe and clear the hole; pour the underwater concrete; pull out the joint pipe; grout the bottom of the wall. It can also meet the requirements when applied to strata with undulating rock surface and hard rock, which cannot meet the requirements of anti-displacement and anti-overturning. It has good soil retaining, water interception, anti-seepage, and durability. The enclosure plays a positive role and has high economic benefits. Compared with the entire underground diaphragm wall entering the rock, it can greatly save costs, and has low noise and pollution.

Description

Construction Method of Outrigger Type Diaphragm Wall

technical field

The invention belongs to the technical field of building construction technology, and specifically designs a construction method of an underground continuous wall with outriggers.

Background technique

Diaphragm wall technology originated in Europe. It was developed based on the method of drilling wells and oil wells using mud and pouring concrete underwater, and has become an effective technology in underground engineering and deep foundation construction. Generally, the underground diaphragm wall can be defined as: using various digging machines, with the help of mud wall protection, dig out a narrow and deep trench underground, and pour appropriate materials in it to form a seepage-proof (water) , retaining and load-bearing functions of the continuous underground wall. After decades of development, the underground diaphragm wall technology has been quite mature, and it has been and is being used in many aspects of foundation engineering instead of many traditional construction methods. Usually underground diaphragm walls are mainly used for: water conservancy and hydropower, open-pit mines and tailings dams (pools) and anti-seepage walls of environmental protection projects; building basements (foundation pits); underground structures (such as underground railways, underground roads, underground parking lots and Underground streets, shops and underground substations, etc.); municipal pipe trenches and culverts; shafts for shield tunneling and other projects; pumping stations, pools; docks, case guards and dry docks; underground oil depots and warehouses; various deep foundations and pile foundations. The reason why the underground diaphragm wall can be used so widely is inseparable from its advantages. The underground diaphragm wall has the following advantages: small vibration and low noise during construction, which is very suitable for urban construction; the wall has high rigidity, When used in foundation pit excavation, it can bear a lot of earth pressure, and rarely cause foundation settlement or landslide accidents. It has become an indispensable retaining structure in deep foundation pit support engineering; the anti-seepage performance is good, because the wall The improvement of the joint form and the construction method makes the underground continuous wall almost impermeable; it can be close to the construction. Due to the advantages mentioned above, we can build the underground diaphragm wall close to the original building. The underground diaphragm wall is suitable for a variety of foundation conditions, and it is applicable to a wide range of foundations, from soft alluvial strata to medium-hard strata, dense gravel layers, all kinds of soft rocks and hard rocks, etc. All foundations can be constructed underground continuous wall wall. It occupies less land, can make full use of the limited ground and space within the red line of the building, and give full play to the investment benefits. It has high work efficiency, short construction period, reliable quality and high economic benefits. However, there are also some shortcomings in the underground diaphragm wall. In underground engineering, the rock surface of the block is shallow, the height difference is different, the excavation of the foundation pit is deep, and the weak stratum (passive soil or strong weathered rock stratum, etc.) at the bottom of the foundation pit is relatively weak. In the shallow case, the general underground diaphragm wall construction scheme cannot meet the displacement and anti-overturning requirements.

Contents of the invention

Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a technical solution for the construction method of the underground diaphragm wall with outriggers, which is suitable for strata with undulating rock surface, hard rock, and cannot meet the anti-displacement and anti-overturning requirements. requirements can also be met.

The construction method of the outrigger type underground diaphragm wall is characterized in that the construction process is as follows:

1) Using measuring equipment, according to the red line boundary pile points and drawings, determine the control points of each axis, form the axis network control, and extend the control points to the area outside the scope of influence of excavation;

2) For the construction of the guide wall, divide the trough section according to the construction investigation situation, the stability of the trough wall and the lifting capacity of the steel cage to ensure the balance of resistance on both sides of the grab bucket of the trough machine;

3) Mud preparation, prepare mud and constantly adjust the proportion according to the actual construction situation to ensure the performance index of the mud, and use mud to protect the wall of the tank to ensure the stability of the tank wall;

4) Grooving construction, use hydraulic grab or drilling rig to drill, rock punching machine impact method for grooving;

5) Outrigger construction, after the groove forming machine excavates to the bedrock surface elevation, use a total station or other measuring equipment to measure the position of the outrigger pile and locate it on the guide wall, and place it at the bottom of the grooved underground continuous wall Pile holes are formed by percussion or rotary drilling;

6) Manufacture and processing of reinforcement cages for underground walls, manufacture reinforcement cages for underground diaphragm walls according to the design drawings, and complete the processing on the reinforcement cage manufacturing platform, and its shape must be straight and regular;

7) Fabrication of outrigger reinforcement cages, alignment and connection with the underground wall reinforcement cages, according to the actual situation and design requirements, complete the outrigger reinforcement cages and section steel components on the production platform, place grouting pipes deep into the outriggers, and place the outriggers The reinforcement cage is positioned between the reinforcement cage trusses of the underground wall, and the leg reinforcement cage and the reinforcement cage of the underground wall are connected and reinforced;

8) Press and release the reinforcement cage, calculate the weight of the entire reinforcement cage, prepare the lifting equipment and formulate the lifting method, lift the reinforcement cage of the underground diaphragm wall to the design position, and position it on the guide wall;

9) Selection of joints. The joint process between the underground continuous wall groove sections is selected according to the use requirements of the underground wall, and I-beams, cross steels, lock pipes, prefabricated pile heads or rubber waterstops are used;

10) Press and release the joints and pour the underwater concrete pipes and clear the holes. Before pouring the concrete, lower the joints at both ends of the steel cage, and then put down the concrete pipes to clean the holes and change the grout;

11) For underwater concrete pouring, within 4 hours after the steel cage is put into the tank, use a concrete pump truck to pour underwater concrete at the same time, at the same speed, and continuously to the outriggers to ensure that the underwater concrete overflows the bottom of the tank at the same time, and then continuously goes underground The diaphragm wall is poured with underwater concrete;

12) Jacking the joint pipe, after the concrete pouring is completed, use the jacking device to pull out the joint pipe after the initial setting;

13) Grouting at the bottom of the wall, after the concrete strength of the underground diaphragm wall reaches 100%, grouting at the bottom of the wall.

The construction method of the outrigger type underground diaphragm wall is characterized in that the length of the groove section in the construction of the process flow guide wall is 4-8m, the inner net width of the guide wall is 30mm larger than the design wall, and the depth of the guide wall is 1.5-8m. 2.5m, the top surface of the guide wall is 100-200m higher than the construction road.

The construction method of the outrigger type underground diaphragm wall is characterized in that the process flow guide wall construction includes the following process flow:

1) Measure and set out, design the longitudinal axis position along the underground diaphragm wall, excavate the guide trench in sections, arrange the gantry panels along the axis direction in sections, and mark the position and elevation of the guide wall;

2) To excavate the groove section, a combination of mechanical excavation and manual trimming is adopted;

3) Pouring concrete cushion;

4) Determine the position of the guide wall on the concrete pad, bind the steel bars, and erect the steel formwork;

5) Carry out concrete pouring, and remove the formwork when the concrete reaches 70% of the design strength.

The construction method of the outrigger type underground diaphragm wall is characterized in that in the process of pressing and releasing joints, pouring underwater concrete conduits, and clearing holes, the concrete conduit is inserted to the bottom of the legs, and the distance from the bottom of the conduit to the bottom of the hole is about 300~500mm.

The construction method of the outrigger type underground diaphragm wall is characterized in that in the process of pressing and releasing joints, pouring underwater concrete conduits, and cleaning holes, the gas lift reverse circulation method is used to clean the holes, and the bottom of the hole is cleared and the pump is separated from the hole. The bottom is 200-500mm.

The invention adds the technology of outrigger setting to the construction technology of the general underground diaphragm wall, and it can also meet the requirements when applied to the rock surface with large undulations and hard rock, which cannot meet the anti-displacement and anti-overturning requirements, such as soil retaining, water interception, It has good impermeability and durability, and plays an active role in solving the load-bearing and enclosure of super-large and super-deep foundation pits. It can be widely used in large-scale deep foundation pit projects such as basements of high-rise buildings, underground parking lots, subways, etc., and has high economic benefits. , compared with the entire underground diaphragm wall into the rock, it can save a lot of cost, and has less noise and less pollution.

Detailed ways

First of all, the pre-construction work is carried out, and the design disclosure, technical disclosure, equipment, personnel, materials, construction water and electricity, etc. are prepared. Using measuring equipment such as total station, theodolite, spirit level, etc., the surveyors determine the control points of each axis according to the red line boundary stake points and drawings, form the axis network control, and extend the control points to the area outside the scope of excavation. The error should be Controls are within specification and design requirements.

Guide wall construction: According to the construction investigation situation, the stability of the tank wall and the lifting capacity of the steel cage, the tank sections are reasonably divided to ensure the balance of resistance on both sides of the grab bucket of the tank machine. The length of the groove section should be 4-8m. The inner net width of the guide wall is generally 30mm larger than the design wall thickness. The top surface of the guide wall is 100-200mm higher than the construction road. The depth of the guide wall is generally between 1.5-2.5m. According to the geological conditions, See the undisturbed soil or solid soil shall prevail. The guide wall is made of cast-in-place reinforced concrete, and the commonly used forms are positive "L" shape and inverted "L" shape. According to the soil quality, groundwater level and the distance between adjacent buildings, select the section form of the guide wall; measure and stake out, design the longitudinal axis position along the underground diaphragm wall and excavate the guide trench in sections, arrange the gantry panels along the axis direction in sections, and mark the position of the guide wall In the process of trench excavation, mechanical excavation and manual trimming shall be combined. Mechanical excavation shall leave 200mm of soil, and then manual trimming shall be made to the elevation, and the original soil shall not be disturbed by over-excavation; Determine the position of the guide wall, bind the steel bars, and then set up the steel formwork. The outside of the standard guide wall is replaced by soil, and the inside is erected. Concrete is poured. Simultaneously vibrate both sides of the guide wall and advance in parallel to prevent mold explosion. The elevation of the top surface of the guide wall in a trough section should maintain a horizontal height difference ≤ 5mm, and the verticality of the guide wall < 1/500; formwork removal and maintenance, the concrete reaches the design strength The formwork can be removed after 70% of the formwork is removed. After the formwork is removed, 100×100 square logs must be supported in the guide wall to prevent the guide wall from being squeezed inward. The construction joints of the guide wall are in the form of concave and convex, and additional reinforcement is added. The surface of the construction joints should be roughened, and the joints should be staggered from the joint joints of the underground diaphragm wall.

Mud preparation: The requirements for using mud in outrigger-type underground diaphragm walls are higher than those of ordinary diaphragm walls. Fresh and high-quality bentonite mud should be used, such as 200 mesh commercial bentonite, dispersant—soda ash and Na ₂ CO ₃ , tackifier— —CMC and other prepared mud can be prepared or adjusted according to the actual situation and design requirements to ensure that the performance indicators of the mud should comply with the national specifications, local specifications and design requirements, and it needs to be sampled and tested to meet the qualified standards before it can be put into use. Use mud to protect the wall to ensure the stability of the tank wall. The amount of mud reserve should not be less than 1.5 to 2 times the volume of the unit tank section. Only the mud that has passed the test during the concrete pouring process can be recycled, and the mud polluted by concrete must be discarded. At the same time, during the trough forming operation, the mud liquid level in the trough is kept at the highest level that will not overflow. When the construction is suspended, the slurry level should not be lower than the top surface of the guide wall by 30cm.

Grooving construction: use methods such as drilling with drilling rigs, rock impact machines or hydraulic grabs for grooving. In this construction method, hydraulic grabs are used for grooving construction. Under the premise of ensuring stability, the groove forming machine is positioned at the minimum angle, firstly clears the excavated groove section, removes waste soil and residual slurry, and then puts in the slurry prepared according to the design requirements, and then discharges the slurry while taking soil. During the process of trough formation, gently lift and slow down to reduce the impact on the trough wall, and always maintain the height of the mud liquid level, and the distance between the liquid level and the top surface of the guide wall is ≤300mm. During the grooving process, the verticality of the hydraulic guide plate grab should be tested with theodolite in the x and y-axis directions according to the grooving equipment, and the deviation should be tracked and corrected so that the verticality is controlled at <1/300. At the end of the groove forming, the groove forming machine will sweep the hole once to remove the silt, and use a special wire brush wall brush to brush the wall. It has reached the standard of no sludge on the wire brush of the wall brush to ensure the connection quality of the groove width section. , and then use a high-pressure rotary pump to clean the steel bars and head steel plates within the joint range.

Outrigger construction: After the groove forming machine excavates to the bedrock surface elevation, use a total station or other measuring equipment to measure the position of the outrigger pile, and locate it on the guide wall, and use it at the bottom of the grooved underground continuous wall. Pile holes are formed by impact or rotary drilling. During the hole forming process, the position of the pile driver should be checked regularly to ensure the horizontal position and verticality of the pile hole. Sampling of rock fragments is carried out regularly to ensure that the depth of rock penetration meets the design requirements.

Manufacture and processing of reinforcement cages for underground walls: manufacture reinforcement cages for underground diaphragm walls according to the design drawings, and complete the processing on the reinforcement cage manufacturing platform. Its shape must be straight and regular. In this construction process, the following issues should be paid attention to: Except for the mechanical connection of steel bars above Φ25, all steel cages are made by electric welding and welding, and galvanized iron wires are not allowed to bind; It can weld steel bars and make steel cages; arrange all kinds of steel bars according to the drawing to ensure that the steel bars are horizontal and vertical, the spacing meets the requirements of the specification, the joints of the steel bars are welded firmly, and the forming dimensions are correct; according to the drawing, the concrete conduit is inserted into the channel. The net size must be at least 50mm larger than the outer diameter of the conduit. The guide reinforcement of the conduit must be welded firmly. Longitudinal reinforcing ribs need to be set, and positioning diagonal tie rods need to be added to the corner-shaped steel cage. After the steel cage is completed, there should be basically no deformation, and the embedded parts should be firm. 20mm; steel cages should be properly equipped with protective layer positioning steel plates on the soil facing surface and excavation surface; in order to ensure the safety of steel cage hoisting, the determination of the lifting point position and the safety of lifting rings and lifting tools should be designed and checked as the final hoisting ring of the steel cage The vertical steel bars on the reinforcement cage of the middle boom must be welded firmly with each intersection point from top to bottom of the intersecting horizontal steel bars; the reserved bars or connectors and pre-installed bars must be welded in strict accordance with the design requirements and drawings. Embed iron parts, and ensure that the positioning accuracy of inserting ribs and embedded parts meets the specified requirements.

Manufacture of outrigger reinforcement cages, alignment and connection with underground wall reinforcement cages: according to the actual situation and design requirements, complete outrigger reinforcement cages and section steel components on the production platform, place grouting pipes deep into the outriggers, and place outrigger reinforcement cages Locate between the steel cage trusses of the underground wall, connect and reinforce the steel cages of the outriggers and the steel cages of the underground wall, such as using the main reinforcement of the outriggers to connect with the main reinforcement of the underground wall through 4 Φ32 pieces; add double hoops outside the trusses to strengthen Wholeness. Welding quality should be ensured when outriggers and components are welded. Symmetrical welding should be adopted. The center line of the outriggers and the steel cage of the underground diaphragm wall must be consistent to ensure the welding size of the outriggers.

Reinforcement cage placement: Calculate the weight of the entire reinforcement cage, reasonably prepare the lifting equipment and formulate the lifting method, lift the reinforcement cage of the underground diaphragm wall to the design position, and position it on the guide wall. In this construction process, the following issues should be paid attention to: before the steel cage is lifted, the welding conditions of the lifting point and the shelf plate must be re-checked, and the lifting can only be started after the welding quality meets the lifting requirements. The lifting and installation of the steel cage should be directed by a special person. Put two pull ropes on the bottom of the steel cage to control the shaking and turning of the steel cage to ensure safety; carefully check the integrity of the spreader and wire rope before lifting, which must meet the requirements of safety regulations. The focus of the inspection on the lifting point is the pulley and Check the quality of the steel wire rope. If the steel wire rope is found to be broken, corroded, and worn to the scrapping standard or the pulley has cracks, etc., it must not be used; check the connection of the guide steel bars in the catheter compartment to ensure that the welding is firm; the steel bars must be removed before lifting. The sundries in the cage can avoid the accident of falling objects in the process of lifting the steel cage; if it is difficult to lower the steel cage, it must not be lowered by impact. If necessary, the steel cage should be lifted out again, and the groove section should be reprocessed before entering the groove; When the cage enters the groove, cut off the reinforcing steel bars in the catheter chamber to ensure that the catheter chamber is straight and smooth; when the steel cage enters the groove, carefully check the integrity of the connector, and if there is any disconnection and connection of the connector or steel bars If the device cap falls off, it must be made up immediately after entering the groove.

Joint selection: The joint process between the underground continuous wall groove sections is selected according to the use requirements of the underground wall. There are mainly I-beams or cross steels, lock pipes, prefabricated joint piles, rubber waterstops, etc. The construction method uses lock pipes The way.

Press and release joints and pour underwater concrete pipes and clear holes: before pouring concrete, lower the locking pipes at both ends of the steel cage, and then lower the concrete pipes. According to the thickness of the wall, choose a wall thickness of 3mm, a diameter of 200-350mm, and a smooth surface on the inner wall. 1. For steel pipes with well-sealed joints, the concrete conduit is inserted to the bottom of the outrigger. The distance from the bottom of the conduit to the bottom of the hole is about 300-500mm. The air-lift reverse circulation method is used to clean the hole and replace the slurry. The distance between the bottom of the cleaning pump and the bottom of the hole is controlled at 200- 500mm, and continuously move up and down, the cleaning time is subject to the export mud index meeting the requirements, not less than 30min.

Underwater concrete pouring: Concrete should be poured within 4 hours after the reinforcement cage is put into the tank. The water barrier plug should use a bladder with the same diameter as the inner diameter of the conduit, and the distance between the bottom of the conduit and the bottom of the tank is about 300-500mm. In the process of pouring concrete, a concrete pump truck is used to pour underwater concrete at the same time, at the same speed, and continuously to the outriggers to ensure that the underwater concrete overflows the bottom of the tank at the same time, and then continuously pours underwater concrete into the underground diaphragm wall. Commercial concrete is generally used, and the slump is controlled at 180-220mm. When pouring concrete, the rising height of the concrete surface should be measured. Each tank (bucket) of concrete must be measured once, and a record should be made to guide the removal of the number of conduit sections and control The depth of the buried pipe should be kept at 2-6 meters, the height difference of the concrete surface should be controlled below 0.3 meters, the rising speed of the concrete surface should not be less than 2m/h, and the locking pipe should be gradually removed. The actual level of concrete pouring should be 50cm higher than the design level to ensure the quality of the top of the wall. When the length of the linear groove section of the underground wall is L>4m, use two conduits to pour concrete, the linear groove section with L<4m uses one conduit to pour concrete, and the special-shaped groove sections use two conduits to pour concrete.

Jacking joint pipe: When pouring the first truck (bucket) concrete, the initial setting test block should be prepared for the first time when the lock pipe is pulled out. When the test block reaches the initial setting, the joint pipe can be lifted, and then lifted every 5 to 10 minutes, the lifting range is about 20cm, and the jacking speed is controlled according to the pressure displayed by the oil pump. A set of anti-compression test blocks shall be made for every 100m ³ of concrete poured in the unit tank section, and a set of impermeability test blocks shall be made for 500m ³ of the whole project. After the concrete pouring is completed and the initial setting is completed, the joint pipe is pulled out by jacking device.

Grouting at the bottom of the wall: After the concrete strength of the underground diaphragm wall reaches 100%, the grouting at the bottom of the wall shall be carried out, and the adjacent underground diaphragm wall shall be grouted at the same time, and the amount of grouting shall be controlled according to the pressure required by the design. The slurry pipe is arranged according to the actual situation of the project. The grouting pipe is made of welded steel pipes, the joints are connected by screws, the bottom of the grouting pipe is tapered, and several rows of small holes are opened, and the openings are tightly wrapped with rubber. The grouting pipe is connected according to the standard length and then bound to the steel cage. The tail section is set according to the actual groove depth. The steel cage is hoisted in the air and then straightened and then connected to the standard section. Make sure that the tail section goes deep into the bottom of the hole after the steel cage is lowered. After 3 days of pouring concrete on the underground diaphragm wall, open holes for clear water to ensure that the pipeline is unimpeded. In this construction process, it should be noted that when the grouting pressure is too high, check whether the pipeline is unblocked before grouting. If the amount of grouting does not meet the design requirements, and the grouting occurs, the grouting should be suspended, and the grouting should be suspended after 24 hours. Supplementary grouting.

Claims (5)

1. supporting leg type underground continuous wall construction method is characterized in that construction technology process is as follows:

1) adopts measureing equipment,, determine each axial line control point, form axle network control system, the control point is extended on the shoveling influence basin zone in addition according to red line boundary marker point and drawing;

2) lead the wall construction, reconnoitre situation, cell wall stability and reinforcement cage hoisting ability according to construction and divide the groove section, to guarantee the resistance equilibrium of scouring machine grab bucket both sides;

3) mud preparation is prepared mud and is constantly adjusted proportioning according to actual construction situation, guarantees the performance indications of mud, and cell wall carries out retaining wall with mud, guarantees that cell wall is stable;

4) trenching construction adopts hydraulic grab or rig creeps into, carry out grooving towards the method for rock machine impact;

5) supporting leg construction after groover excavates the bedrock surface absolute altitude, is measured supporting leg position, stake position and is navigated to total powerstation or other measureing equipments and lead on the wall, at the diaphragm wall bottom land of grooving with impact type or rotary drill mode pile hole;

6) the subterranean wall reinforcing cage is made, is processed, and makes the diaphragm wall reinforcing cage according to design drawing, and finishes processing on reinforcing cage making platform, and its profile must be straight, regular;

7) the supporting leg reinforcing cage is made, with the contraposition of subterranean wall reinforcing cage be connected, according to actual conditions and designing requirement, on the making platform, finish members such as supporting leg reinforcing cage and shaped steel, place Grouting Pipe and go deep into supporting leg, the supporting leg reinforcing cage is positioned between the subterranean wall reinforcing cage truss, the supporting leg reinforcing cage is connected, reinforces with the subterranean wall reinforcing cage;

8) reinforcing cage calculates whole reinforcing cage weight by putting, and preparation lifting appliance and formulate hoisting method, lifting diaphragm wall reinforcing cage be down to design attitude, and is positioned at and leads on the wall;

9) joint is selected, and the instructions for use of wall is selected for use under the joint technology base area between underground continuous wall groove segment, adopts i iron, cross steel, fore shaft pipe, prefabricated pile extension head or rubber fastening band;

10) by putting joint and cast underwater concrete conduit, clear hole, before concrete casting, transfer joint, put down tremie afterwards, carry out clearly the hole and change slurry in the reinforcing cage two ends;

11) underwater concreting in 4 hours after reinforcing cage is gone into groove, adopts the concrete mixer while, pours into a mould underwater concrete with fast, continuous toward supporting leg, guarantees that underwater concrete overflows bottom land simultaneously, continuous afterwards past diaphragm wall pouring underwater concrete;

12) pull junction block, after concrete pouring finishes, adopt lift-up device that mouthpiece is pulled extraction after the initial set;

13) wall rising pouring slurry carries out wall rising pouring slurry after the diaphragm wall concrete strength reaches 100%.

2. supporting leg type underground continuous wall construction method as claimed in claim 1, it is characterized in that it is 4～8m that the length of groove section in the wall construction is led in described technological process, lead the big 20mm of span width ratio design wall within the walls, leading the wall degree of depth is 1.5～2.5m, leads the wall end face than the high 100～200m of builder's road.

3. supporting leg type underground continuous wall construction method as claimed in claim 1 is characterized in that described technological process leads wall construction and comprise following technological process:

1) measure setting-out, along diaphragm wall design longitudinal axis position, the excavation section by section guide channel, segmentation is arranged sight rail along axis direction, marks to lead wall displacement and absolute altitude;

2) box cut section adopts mechanical equivalent of light excavation and manual amendment to combine;

3) fluid concrete bed course;

4) on the concrete mats aspect, make and lead wall displacement, assembling reinforcement, upright again steel form;

5) carry out concrete pouring, when concrete reach design strength 70% after form removal.

4. supporting leg type underground continuous wall construction method as claimed in claim 1, it is characterized in that described by putting in joint and cast underwater concrete conduit, the clear hole technological process, tremie is inserted into the supporting leg bottom, and mouth is about 300～500mm at the bottom of the conduit at the bottom of the hole.

5. supporting leg type underground continuous wall construction method as claimed in claim 1 is characterized in that describedly utilizing the gaslift crossover-circulating type method to carry out hole clearly by putting in joint and cast underwater concrete conduit, the clear hole technological process, is 200～500mm at the bottom of the hole at the bottom of the pump of clear hole.