CN111379252A

CN111379252A - Diaphragm wall construction method

Info

Publication number: CN111379252A
Application number: CN201811610710.0A
Authority: CN
Inventors: 赵余夫; 傅珺; 邓文全; 陈洁; 鲍廉梵; 袁醒神; 蔡晓瑛; 许颖儿
Original assignee: Hongrun Construction Group Co Ltd
Current assignee: Hongrun Construction Group Co Ltd
Priority date: 2018-12-28
Filing date: 2018-12-28
Publication date: 2020-07-07

Abstract

The invention discloses a construction method of a diaphragm wall, which comprises the steps of determining the construction position of the diaphragm wall and the construction position of a guide wall in a region to be constructed; conducting guide wall construction at the guide wall construction position; carrying out diaphragm wall construction at the diaphragm wall construction position; wherein, in the process of the continuous wall construction, a mud system capable of being recycled is adopted, and the process flow of the mud system comprises the preparation and the use of fresh mud, the recovery, the separation, the precipitation, the screening and the centrifugal separation of the recyclable mud to purify the mud for recycling; the colloid rate of the fresh mud is more than 98%, and the thickness of the mud skin is less than or equal to 1 mm/30 min; the water loss rate of the recyclable slurry is less than 30 mg/min, the sand content is less than 4%, the pH value is 8-10, and the viscosity is 18-22 seconds. The construction method of the continuous wall adopts the mud system which can be recycled, can carry out regeneration treatment on the mud in the construction process, is energy-saving and environment-friendly, and can reduce the construction cost.

Description

Diaphragm wall construction method

Technical Field

The invention relates to the field of constructional engineering, in particular to a diaphragm wall construction method.

Background

The underground continuous wall is a foundation engineering, and adopts a trenching machine on the ground, and under the condition of slurry wall protection, a long and narrow deep groove is excavated along the peripheral axis of the deep excavation engineering, after the groove is cleaned, a steel reinforcement cage is hung in the groove, then underwater concrete is poured by using a conduit method to construct a unit groove section, and the steps are carried out section by section, so that a continuous reinforced concrete wall is constructed underground to be used as a structure for intercepting water, preventing seepage, bearing and retaining water.

The mud retaining wall is needed in the construction process of the underground continuous wall, the mud exerts pressure on the wall of the groove to protect the shape of the dug deep groove from changing, and the mud is replaced by pouring concrete. The slurry has the function of forming a watertight mud skin on the wall of the tank, so that the hydrostatic pressure of the slurry effectively acts on the wall of the tank, the seepage of underground water and the peeling of the tank wall are prevented, the stability of the wall surface is kept, and the slurry also has the functions of suspending the soil residues and carrying the soil residues out of the ground. In the existing construction process, the mud is mostly used by adopting a chemical method to treat or discard old mud after the index of the mud is deteriorated, and then new mud is used. The construction cost is high and the environment is not protected. And the existing diaphragm wall structure can easily leak at the joint in the construction of the deep foundation pit.

Disclosure of Invention

The invention provides a diaphragm wall construction method, which aims to solve the technical problems that in the diaphragm wall construction method in the prior art, slurry is treated by a chemical method or old slurry is abandoned in the construction process, so that the construction cost is high, the diaphragm wall construction method is not environment-friendly, and leakage is easy to occur at the diaphragm wall joint.

In order to achieve the aim, the ground connecting wall construction method provided by the invention comprises the following steps of determining a ground connecting wall construction position and a guide wall construction position in a to-be-constructed area; conducting guide wall construction at the guide wall construction position; after the guide wall construction is finished, performing diaphragm wall construction on the diaphragm wall construction according to a diaphragm wall design drawing and setting a construction sequence; wherein, in the process of the continuous wall construction, a mud system capable of being recycled is adopted, and the process flow of the mud system comprises the preparation and the use of fresh mud, the recovery, the separation, the precipitation, the screening and the centrifugal separation of the recyclable mud to purify the mud for recycling; the colloid rate of the fresh mud is more than 98%, and the thickness of the mud skin is less than or equal to 1 mm/30 min; the water loss rate of the recyclable slurry is less than 30 mg/min, the sand content is less than 4%, the pH value is 8-10, and the viscosity is 18-22 seconds.

Preferably, the preparation method of the fresh slurry comprises raw material experiments, weighing and feeding materials, mixing bentonite and water for 5 minutes, mixing sodium carboxymethylcellulose (CMC) and sodium carbonate with water for 5 minutes, mixing and stirring the two for 3 minutes, measuring the performance index of the slurry, and swelling for 24 hours for later use.

Preferably, the mud system process further comprises treating the waste mud having a PH greater than 14 or a viscosity greater than 50 seconds.

Preferably, the construction method further comprises the steps of determining the consumption degree of bentonite, soda ash and sodium carboxymethyl cellulose (CMC) in the purified slurry according to the performance index of the purified slurry, and supplementing slurry components to the purified slurry according to the performance index obtained by the test to form regenerated slurry; in the continuous wall use project, the regenerated mud needs to be used in admixture with the fresh mud.

Preferably, the purified slurry is supplemented with bentonite, soda ash, sodium carboxymethylcellulose (CMC) and water by supplementing the purified slurry with components to substantially restore the original wall-protecting properties of the purified slurry.

Preferably, the diaphragm wall construction comprises: dividing groove sections at the construction positions of the diaphragm walls, and performing diaphragm wall grooving construction; according to the grooving construction condition of the diaphragm wall, performing wall brushing treatment on the wall of the grooving groove of the diaphragm wall; carrying out bottom cleaning treatment on the diaphragm wall grooving; according to the bottom cleaning condition, hoisting a reinforcement cage in the underground diaphragm wall grooving; after the construction of the reinforcement cage is completed, performing the construction of a ground connecting wall grooving section joint; and grouting the wall bottom of the diaphragm wall to complete the construction of the diaphragm wall.

Preferably, the construction of the diaphragm wall further comprises the steps of embedding grouting sleeve valve pipes at the joints of the diaphragm wall, and grouting and reinforcing the superfine cement sleeve valve pipes after the construction of the diaphragm wall is completed.

Preferably, the construction of the diaphragm wall further comprises the step of arranging two jet grouting piles at the joint of the diaphragm wall.

Preferably, the construction method further comprises the step of performing waste treatment on the slurry generated by the bottom cleaning treatment.

Preferably, the wall brushing treatment mainly comprises the steps of adopting a forced wall brushing machine, and utilizing a steel wire rope hanging heavy hammer as a guide to enable the wall brushing device to be tightly attached to a wall connecting joint in the wall brushing process; the inclined rib plates are arranged inside the wall brushing machine, so that the vertical force of slurry on the wall brushing machine is converted into a horizontal component force in the process of lowering the wall brushing machine, the wall brushing machine is tightly connected with a wall joint, and the operation is repeated for a plurality of times until no attachments exist on the wall brushing machine.

Through the technical scheme provided by the invention, the invention at least has the following technical effects:

the method for constructing the diaphragm wall is advanced in diaphragm wall construction, after the strength of the diaphragm wall reaches a design value, a diaphragm wall experiment groove is excavated, construction parameters of a high-pressure jet grouting pile are determined according to the grooving condition of the diaphragm wall experiment groove to carry out jet grouting pile construction, and diaphragm wall construction is carried out after the jet grouting pile construction is finished. By the construction method, the wall collapse during the diaphragm wall construction can be avoided, the diaphragm wall construction effect is ensured, and the construction period can be shortened. In addition, the construction method of the diaphragm wall adopts a mud system which can be recycled in the construction process, thereby reducing the construction cost and being environment-friendly. By embedding the grouting sleeve valve pipes at the joints of the diaphragm walls and grouting and reinforcing the superfine cement sleeve valve pipes after diaphragm wall construction is completed, the construction method disclosed by the invention effectively avoids leakage at the joints of the diaphragm walls and effectively ensures diaphragm wall construction effect.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

Fig. 1 is a flowchart of a diaphragm wall construction method provided by the present invention.

FIG. 2 is a process flow diagram of a middle circulation slurry system of the diaphragm wall construction method provided by the invention.

FIG. 3 is a process flow chart of slurry preparation in the diaphragm wall construction method provided by the invention.

Fig. 4 is a schematic structural diagram of a main guide wall in the diaphragm wall construction method provided by the invention.

Fig. 5 is a schematic structural view of an auxiliary guide wall of the diaphragm wall construction method provided by the present invention.

Fig. 6 is a schematic view of wall brushing treatment in the diaphragm wall construction method provided by the invention.

Fig. 7 is a schematic structural view of underwater concrete pouring in the diaphragm wall construction method of the present invention.

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration and explanation only, not limitation.

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

In the present invention, unless specified to the contrary, use of the terms of orientation such as "upper, lower, top, bottom" or the like are generally described with respect to the orientation shown in the drawings or the positional relationship of the components with respect to each other in the vertical, or gravitational direction.

The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

Referring to fig. 1, the present invention provides a diaphragm wall construction method, which mainly includes the steps of S1 determining a diaphragm wall construction position and a guide wall construction position in a region to be constructed; conducting guide wall construction at the guide wall construction position; and S2, after the guide wall construction is finished, performing diaphragm wall construction on the diaphragm wall construction according to a diaphragm wall design drawing and setting a construction sequence. Step S2 specifically includes: s201, dividing groove sections at the construction position of the diaphragm wall, and performing diaphragm wall grooving construction; s202, performing wall brushing treatment on the wall of the groove forming wall of the diaphragm wall according to the diaphragm wall grooving construction condition; s203, performing bottom cleaning treatment on the diaphragm wall grooving; s204, manufacturing a reinforcement cage according to the bottom cleaning condition, and hoisting the reinforcement cage in the diaphragm wall grooving; s205, after the construction of the reinforcement cage is finished, installing a fore shaft pipe and performing secondary bottom cleaning; s206, pouring underwater concrete; and S207, performing wall bottom grouting on the diaphragm wall to complete the construction of the diaphragm wall.

Step S205 further includes installing a concrete conduit; in step S206, the locking pipes are also supplied and pulled out, which will be described in detail later.

In the embodiment of the invention, a recyclable slurry system is adopted in the process of continuous wall grooving construction, and the process flow of the slurry system comprises the preparation and the use of fresh slurry, the recovery, the separation, the precipitation, the screening and the centrifugal separation of the recyclable slurry to obtain purified slurry for recycling; the colloid rate of the fresh mud is more than 98%, and the thickness of the mud skin is less than or equal to 1 mm/30 min; the water loss rate of the recyclable slurry is less than 30 mg/min, the sand content is less than 4%, the pH value is 8-10, and the viscosity is 18-22 seconds.

Referring to fig. 2, a process flow diagram of a middle circulation slurry system of the diaphragm wall construction method provided by the present invention is shown. The slurry system process comprises the following steps: preparing fresh slurry, storing the fresh slurry, recovering the slurry in the construction tank, performing coarse screening separation and sedimentation tank separation on the recovered slurry, and separating the slurry by using a cyclone vibrating screen and a centrifugal machine to obtain purified slurry. The deteriorated slurry from which the purified slurry has been separated is discarded, and the resulting purified slurry is stirred with feed slurry to obtain regenerated slurry and stored.

In the above slurry system process, fresh slurry is mainly formulated from the following slurry materials: a) bentonite, b) water, c) a dispersant, d) a tackifier, e) a weighting agent, f) a leakage preventer. Wherein the water can be tap water, the dispersant can be sodium carbonate (Na2CO3), the tackifier can be sodium carboxymethylcellulose (CMC), the weighting agent can be 200-mesh barite powder, and the leakage-proof agent can be pulp fiber. The performance indicators for the fresh mud may be as shown in table one below.

Table one: performance index table of fresh mud

The basic mix ratios of fresh mud in the above mud system process are shown in table two below.

Table two: fresh mud mixing ratio

Slurry material	Bentonite clay	Soda ash	CMC	Tap water
					1m³Feeding amount (kilogram)	130	4.5	1	950

Furthermore, in embodiments of the invention, the slurry cleaned out of the bottoming process should be discarded. In the process of pouring concrete and recycling the slurry, when the slurry index exceeds any one of the following indexes, the slurry is discarded: viscosity greater than 50, pH greater than 14, and specific gravity greater than 1.25.

As shown in fig. 3, a process flow diagram for preparing mud according to the present invention is provided. The preparation method of the slurry comprises raw material experiment, weighing and feeding materials, respectively stirring bentonite and water for 5 minutes, and sodium carboxymethylcellulose (CMC) and sodium carbonate with water for 5 minutes, mixing and stirring the two mixtures for 3 minutes, measuring the slurry performance index, and swelling for 24 hours for later use. The slurry prepared by the method is fresh slurry.

The mud circulating system adopts a 3LM type mud pump for conveying, a 4PL type mud pump for recovering, and a mud circulating pipeline is formed by a mud pump and a hose. The index of the circulating slurry in the grooving process is shown in the following table three.

Table three: index of circulating slurry in grooving construction process

In the embodiment of the invention, after the circulating mud is separated and purified, although a lot of soil residues mixed in the circulating mud are removed, the original wall protection performance of the circulating mud is not recovered, because the mud is in contact with foundation soil and underground water during the use process and forms a mud skin on the surface of a groove wall, components such as bentonite, calcined soda, CMC and the like in the mud are consumed, and the wall protection performance weakened by the pollution of the mud component and harmful ions in concrete is generated, therefore, after the circulating mud is separated and purified, the performance index of the purified mud is required to be adjusted to recover the original wall protection performance of the circulating mud.

In the process flow of the circulating slurry system, the purified slurry also needs to be regenerated. It is often necessary to first test the clean mud performance index. Through testing performance indexes such as specific gravity, PH value and viscosity of the purified slurry, the consumption degree of main components such as bentonite, soda ash and CMC in the purified slurry is known. Then, the purified slurry is supplemented with slurry components to substantially restore the original wall-protecting properties of the purified slurry. The supplemented slurry components can be used for purifying the slurry and supplementing components such as bentonite, soda ash, CMC and the like, and can be supplemented by adopting a method of re-feeding and stirring. If a large amount of purified slurry needs to be regenerated, concentrated fresh slurry is prepared first and then added into the purified slurry to be flushed and stirred by a slurry pump to adjust the performance index of the purified slurry, so that the original wall protection performance is basically recovered, and the regenerated slurry is obtained. Although the regenerated mud basically recovers the original wall protection performance, the performance of the regenerated mud is not as excellent as that of the fresh mud, so the regenerated mud is not suitable for being used alone and is mixed with the fresh mud for use.

In the construction engineering, the deteriorated slurry refers to slurry which is deteriorated and deteriorated due to cement pollution when the wall body concrete is poured and the concrete contacts with the deteriorated slurry, and the over-standard slurry which has the viscosity and the specific gravity exceeding standards and is difficult to separate and purify so as to reduce the viscosity and the specific gravity of the over-standard slurry is repeatedly used for many times. In a normal case, the deteriorated slurry is temporarily stored in a slurry tank and then shipped to a tanker and discarded. In special cases where the slurry cannot be shipped and disposed of by tanker truck, the degraded slurry is treated by dewatering or curing the slurry.

In addition, in the process flow of the circulating mud system, quality control of the mud is required. The quality control mainly comprises the following three aspects that 1, raw materials used for preparing the slurry meet the technical performance requirements, and the mixing proportion of the slurry during preparation is met. 2. And (4) carrying out secondary quality index detection every time in the slurry preparation, storing the newly mixed slurry for 24 hours before using, and continuously stirring by using a slurry pump in a slurry pool. 3. The preparation and use of the slurry are strictly carried out according to technical operation requirements, sampling tests are carried out at proper time and positions in different construction stages, the workability of new slurry is judged according to test results, and measures such as regeneration, correction of mixing proportion and the like are taken to ensure the grooving precision and the construction safety. The test items, sampling time and location of the slurry quality control are shown in table four below.

Table four: mud quality control parameter table

As shown in fig. 4 and 5, the method for constructing a diaphragm wall according to the present invention includes steps of S1, excavating a groove with a backhoe excavator during the construction of the diaphragm wall, manually repairing a slope after the excavation is completed, then erecting a diaphragm wall formwork, placing a steel mesh in the formwork, symmetrically pouring the diaphragm wall, detaching the formwork after the strength reaches 70%, setting 80 × mm wood supports after the formwork is detached, setting a distance of 1500 × mm, and backfilling soil in the groove of the diaphragm wall to ensure construction safety, wherein the diaphragm wall of the present embodiment is of a cast-in-place reinforced concrete structure, and the concrete is C20 and the thickness of a protective layer is 20 mm.

As shown in fig. 4, the main body guide wall 1 includes two inverted L-shaped guide wall bodies 11, wherein at least two support rods 3 are disposed between the two guide wall bodies 11; the side wall of the guide wall body 11 is provided with a protective layer 13, and a concrete cushion layer 12 is arranged on the lower side of the guide wall body. In the embodiment of the invention, the depth of the main guide wall is 1.85m, the thickness of the guide wall is 0.2m, the soil facing side flanging is 1.0m, the excavation side flanging is 0.6m, and the thickness of the flanging is 0.2m, and the structure and the reinforcing bars of the main guide wall are shown in figure 4.

As shown in fig. 5, the auxiliary guide wall 2 includes two inverted L-shaped guide wall bodies 21, wherein at least two support rods 3 are disposed between the two guide wall bodies 21; the side wall of the guide wall body 21 is provided with a protective layer 23, and a concrete cushion 22 is arranged on the lower side of the guide wall body. The depth of the auxiliary guide wall in the embodiment of the invention is 1.5m, the thickness of the guide wall is 0.2m, the flanging is 0.85m, the thickness of the flanging is 0.2m, and the structure and the reinforcing bars of the guide wall are shown in figure 5.

After the concrete of the guide wall is poured and the inner formwork is removed, upper and lower support pairs with the interval of 1m and the horizontal interval of 1.5m are arranged in the guide wall ditch, and earth is filled back into the guide wall ditch so as to prevent the guide wall from displacing. When the guide wall concrete is naturally cured to over 70 percent of the design strength, the grooving construction can be carried out. The embodiment of the invention ensures the grooving effect and the verticality of the diaphragm wall through the opposite support arrangement of the guide walls.

In the grooving construction of step S201 in the implementation of the invention, a grooving machine is adopted for the groove digging section, the grooving machine is provided with a verticality display instrument and an automatic deviation correcting device, and the grooving section can be reasonably adjusted at the corner of the enclosure structure in order to ensure the grooving quality and the grooving size. The unit groove segments are then excavated in a predetermined order. The excavating sequence of the unit groove sections is as follows: 1. the single holes at the two ends of the groove section are dug firstly, or the method of digging the second hole after the first hole is dug and jumping for a distance is adopted, so that the partition wall which is not dug is left between the two single holes, the grab bucket can be balanced in force when the single holes are dug, the deviation can be effectively corrected, and the straightness of the groove is ensured. 2. Firstly, digging a single hole, and then digging a partition wall. Because the length of the hole partition wall is less than the opening length of the grab bucket, the grab bucket can be sleeved on the partition wall to dig, the grab bucket can be balanced in force, the deviation is effectively corrected, and the grooving perpendicularity is guaranteed. 3. And sleeving and digging along the length direction of the groove. 4. After the single hole and the hole partition wall are dug to the designed depth, the grab bucket is sleeved and dug along the length direction of the groove, when the grab bucket is used for digging the single hole and the partition wall, concave and convex surfaces formed by different verticality of the formed groove of the grab bucket are repaired to be smooth, and the groove section is ensured to have good linearity in the transverse direction. 5. Digging and removing sediment at the bottom of the tank: when the grab bucket is sleeved and excavated along the length direction of the groove, the grab bucket is lowered to the designed depth of the groove section to excavate and remove sediments at the bottom of the groove.

In step S202, the wall brushing process is performed on the wall of the underground continuous wall grooving machine according to the construction situation of the underground continuous wall grooving machine. When the groove wall construction of the underground continuous wall groove is carried out, a layer of mud skin is often attached to the joint, the quality of the groove wall joint is affected, and water leakage of the joint part occurs. Therefore, the wall brushing treatment is required to be performed on the groove wall, as shown in fig. 6, which is a schematic view of the wall brushing treatment of the diaphragm wall construction method provided by the present invention. The wall brushing method mainly adopts a forced wall brushing machine 4 which comprises a directional pulley 41, a steel wire rope hanging heavy hammer 42 is used as a guide to enable the wall brushing machine to be tightly attached to a joint in the wall brushing process, the wall brushing effect is ensured, in addition, an inclined ribbed plate is arranged inside the wall brushing machine, in the lowering process, the vertical force of slurry on the wall brushing machine is converted into a horizontal component force, the wall brushing machine is enabled to be tightly attached to the joint, and the process is repeated for a plurality of times until no attachments exist on the wall brushing machine.

After the wall brushing process is completed, a bottoming process is performed on the wall-connected trench in step S203. The bottom cleaning treatment method can adopt a precipitation method or a displacement method. The thickness of the sediment of the bottom cleaning is less than or equal to 100 mm. If the precipitation method is adopted, because the slurry has certain specific gravity and viscosity, the sedimentation of the soil residues in the slurry is retarded, and the time for the soil residues to sink to the bottom of the tank is required, so that the bottom cleaning by the precipitation method needs to be started after the tank forming is finished for a certain time, and the hydraulic grab bucket for tank digging operation is used for directly digging and removing the sediment at the bottom of the tank. If a replacement method is adopted, the method is carried out after the grab bucket directly digs sediment at the bottom of the bucket, and the small soil sediment which cannot be dug by the grab bucket is removed. The replacement method adopted in the embodiment generally uses a Dg100 air lift device, the Dg100 air lift device is suspended by a crane to enter the tank, and an air compressor is used for delivering compressed air to suck and remove soil and slag sludge deposited at the bottom of the tank by a mud reverse circulation method. After the bottom cleaning by the replacement method, the slurry needs to be replaced, and the slurry replacement is the continuation of the bottom cleaning operation by the replacement method. When the air liquid lifter does not suck the soil residue any more after reciprocating at the bottom of the tank and the measured thickness of the settled residue at the bottom of the tank is less than 10 cm, the air liquid lifter can be stopped moving and the slurry which does not meet the quality requirement at the bottom of the tank can be replaced.

During bottom cleaning treatment construction, whether bottom cleaning slurry changing is qualified or not needs to be confirmed, a sampling test is taken as a standard, when the slurry sampling test data of each sampling point at the tank bottom meets a specified index, the density of slurry at the 200mm position of the tank bottom is not more than 1.15, the viscosity is less than 30 seconds, the pH value is 10-12, the sand content is less than 4%, and the bottom cleaning slurry changing is qualified.

The quality of the slurry is required to be controlled in the construction process of the invention, and the control standard of the slurry quality is shown in the following table five.

Table five: standard of mud quality control

According to the above table, the specific gravity of the slurry is less than 1.10 when the slot is formed, and the specific gravity of the slurry is less than 1.15 after the hole is cleaned.

After the bottom cleaning treatment is finished, the fore shaft pipe is immediately hoisted and assembled by a crawler crane in sections and vertically inserted into the grooving. The center of the locking pipe is matched with the designed central line, and the bottom of the locking pipe is inserted into the groove bottom by 50-80 cm to ensure close contact and prevent concrete from flowing backwards. The joint of the upper port and the guide wall is wedged and compacted by wood tenons, and the back side of the fore shaft pipe is filled with sand and stone materials to prevent inclination.

In step S204, a reinforcement cage is manufactured and is hoisted in the underground diaphragm wall grooving; and in step S205, the fore shaft pipe is installed and the secondary bottoming process is performed. And before the step S207 of grouting the wall bottom of the underground diaphragm wall, the method also comprises the step S206 of pouring underwater concrete and lifting the fore shaft pipe so as to finish the construction of the underground diaphragm wall. In addition, the construction of the ground connecting wall grooving section joint is also included.

Fig. 7 is a schematic structural view of underwater concrete pouring in the diaphragm wall construction method of the present invention. And proportioning the concrete of the continuous wall according to a construction standard which is higher than the strength of the fluid concrete design grade by one grade. In an embodiment of the invention, concrete is discharged directly from the mixer truck and poured through the concrete guide 7 via the crawler 6 and the hopper 61. The grooving horizontal plane is provided with an insert plate 51 through which the concrete conduit 7 can pass. The horizontal arrangement distance of the concrete guide pipe 7 is not more than 3m, the distance from the end part of the groove section is not more than 1.5m, and the lower end of the concrete guide pipe is about 50cm away from the groove bottom; before pouring concrete, a water-proof plug is hung in the position close to the slurry surface in the concrete guide pipe. In order to ensure the tightness and firmness of the concrete conduit connection, the water-proof bolt passing test is carried out by trial assembly before use.

According to the embodiment of the invention, the concrete pouring in the actual construction process meets the following conditions: 1. after the reinforcement cage is sunk in place, concrete should be poured in time, and the time for pouring the concrete should not exceed 6 hours; 2. the initial irrigation quantity of the concrete is required to ensure that the depth of the embedded pipe is not less than 500 mm; 3. the concrete should be poured evenly and continuously, so the pouring interruption time is not more than 30 min; 4. in the concrete pouring process, the depth of the conduit embedded into the concrete is controlled to be 2-4m, and the height difference of the concrete in two adjacent conduits is not more than 0.5 m; 5. the concrete can not overflow the guide pipe and fall into the groove; 6. controlling the concrete pouring speed to be 3-5 m/h; 7. the displaced mud should be processed in time and should not overflow the ground;8. the concrete pouring height is preferably 300-500 mm higher than the design height; 9. concrete per 100m of each unit groove section³Preparing a group 1 of compressive strength test pieces; the samples of the permeation resistant pressure test piece 1 were set, and 6 samples were each set. The above conditions can effectively improve the construction quality of the underwater concrete pouring field so as to improve the quality of the diaphragm wall.

The lifting of the fore shaft pipe and the concrete pouring are combined, the concrete pouring record is used as a control basis for the lifting of the fore shaft pipe, and according to the embodiment of the invention, the pulling is started about 3.5-4 hours after the concrete pouring is started. The amplitude of the pipe is not more than 10 cm, the pipe is lifted every 10-20 minutes, the amplitude of the pipe is not more than 20 cm, the sinking of the fore shaft pipe is observed, and the fore shaft pipe is completely pulled out once and cleaned and dredged in time after the concrete pouring is finished for 6-8 hours.

According to the embodiment of the invention, the continuous wall bottom grouting in step S206 of the invention is implemented by inserting a steel pipe or a black iron pipe with an inner diameter not less than 30mm into the lower portion of the underground continuous wall by 1 m. After the grouting pipes are connected, the joints are wrapped by electric adhesive tapes to form two layers so as to prevent slurry from leaking into the pipes. Each underground wall is provided with 2 grouting pipes, and the grouting amount of each grouting pipe is not less than 2m³And adopting a hole-separating and jumping-pouring mode for construction. Controlling the grouting pressure to be 0.2-0.5 Mpa; the flow is controlled to be 10-25L/min; after the strength of the underground continuous wall reaches 100%, wall toe grouting reinforcement construction is carried out through pre-embedded grouting pipes, and grouting in each hole is not less than 2m³。

In the process of constructing the deep foundation pit, the joint of the diaphragm wall is easy to leak, in order to enhance the quality of the diaphragm wall, the invention also comprises the steps of embedding grouting sleeve valve pipes in the joint of the diaphragm wall, and grouting and reinforcing the superfine cement sleeve valve pipes after the diaphragm wall construction is finished. Or/and the construction of the diaphragm wall also comprises the step of arranging two phi 800@600 jet grouting piles at the joint of the diaphragm wall on the outer side of the foundation pit before earth excavation.

The method of the embodiment of the invention can avoid the collapse of the wall of the diaphragm wall during the construction of the diaphragm wall, ensure the construction effect of the diaphragm wall, simultaneously, the high-pressure rotary jet grouting tool has a guiding function on the excavation of the diaphragm wall, effectively ensure the verticality of the diaphragm wall, have low strength requirement on guide wall concrete during the rotary jet grouting tool construction, reduce the equal-strength time of the guide wall when the rotary jet grouting pile construction is carried out after the guide wall construction, and shorten the construction period.

In addition, the construction method of the diaphragm wall adopts a mud system which can be recycled in the construction process, thereby reducing the construction cost and being environment-friendly. By embedding the grouting sleeve valve pipes at the joints of the diaphragm walls and grouting and reinforcing the superfine cement sleeve valve pipes after diaphragm wall construction is completed, the construction method disclosed by the invention effectively avoids leakage at the joints of the diaphragm walls and effectively ensures diaphragm wall construction effect.

The preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims

1. A construction method of a diaphragm wall is characterized by comprising the following steps:

determining a diaphragm wall construction position and a guide wall construction position in a to-be-constructed area; conducting guide wall construction at the guide wall construction position; after the guide wall construction is finished, performing diaphragm wall construction on the diaphragm wall construction according to a diaphragm wall design drawing and setting a construction sequence;

wherein, in the process of the continuous wall construction, a mud system capable of being recycled is adopted, and the process flow of the mud system comprises the preparation and the use of fresh mud, the recovery, the separation, the precipitation, the screening and the centrifugal separation of the recyclable mud to purify the mud for recycling; the colloid rate of the fresh mud is more than 98%, and the thickness of the mud skin is less than or equal to 1 mm/30 min; the water loss rate of the recyclable slurry is less than 30 mg/min, the sand content is less than 4%, the pH value is 8-10, and the viscosity is 18-22 seconds.

2. The construction method according to claim 1, wherein the preparation method of the fresh slurry comprises a raw material experiment, weighing and charging materials, mixing bentonite and water for 5 minutes, mixing sodium carboxymethylcellulose (CMC) and sodium carbonate with water for 5 minutes, mixing the two materials for 3 minutes, measuring the slurry performance index, and swelling for 24 hours for later use.

3. The method of claim 1, wherein the mud system process further comprises treating a waste mud having a PH greater than 14 or a viscosity greater than 50 seconds.

4. The method of claim 1, further comprising determining a degree of consumption of bentonite, soda ash and sodium carboxymethyl cellulose (CMC) in the purified slurry for testing a performance index of the purified slurry, and supplementing slurry components to the purified slurry according to the performance index obtained by the testing to form a regenerated slurry; in the continuous wall use project, the regenerated mud needs to be used in admixture with the fresh mud.

5. The method of claim 3, wherein the purified slurry is supplemented with bentonite, soda ash, sodium carboxymethylcellulose (CMC) and water to substantially restore the original wall-protecting properties of the purified slurry.

6. The construction method according to claim 1, wherein the diaphragm wall construction comprises: dividing groove sections at the construction positions of the diaphragm walls, and performing diaphragm wall grooving construction; according to the grooving construction condition of the diaphragm wall, performing wall brushing treatment on the wall of the grooving groove of the diaphragm wall; carrying out bottom cleaning treatment on the diaphragm wall grooving; manufacturing a reinforcement cage according to the bottom cleaning condition, and hoisting the reinforcement cage in the underground diaphragm wall grooving; after the construction of the reinforcement cage is completed, performing the construction of a ground connecting wall grooving section joint; and grouting the wall bottom of the diaphragm wall to complete the construction of the diaphragm wall.

7. The construction method according to claim 6, wherein the underground diaphragm wall construction further comprises embedding grouting sleeve valve pipes at joints of the underground diaphragm wall, and performing grouting reinforcement on the superfine cement sleeve valve pipes after the underground diaphragm wall construction is completed.

8. The method of claim 6, wherein the constructing of the diaphragm wall further comprises installing two jet grouting piles at the joint of the diaphragm wall.

9. The method of claim 6, further comprising disposing of slurry produced by the bottoming process.

10. The construction method according to claim 6, wherein the wall brushing process mainly comprises the steps of adopting a forced wall brushing machine, and using a steel wire rope hanging heavy hammer as a guide to enable the wall brushing machine to be tightly attached to a ground wall joint in the wall brushing process; the inclined rib plates are arranged inside the wall brushing machine, so that the vertical force of slurry on the wall brushing machine is converted into a horizontal component force in the process of lowering the wall brushing machine, the wall brushing machine is tightly connected with a wall joint, and the operation is repeated for a plurality of times until no attachments exist on the wall brushing machine.