CN103266614A - Sublevel retreating type two-fluid composite grouting construction method for deep foundation pit of sandy gravel stratum - Google Patents

Abstract

The invention discloses a subsection retreat double-liquid composite grouting construction method for deep foundation pits in sand and pebble formations. The specific steps are: determining the grouting reinforcement scheme; measuring and setting out lines on site; drilling holes, and lowering the double grouting pipes after the holes are formed , and then install the pipe puller and pull out the drill pipe; grout preparation; grouting, using the injection method of the septum hole, the cement-water glass slurry and the modified water glass slurry are injected in combination, and the conversion of the grout is based on the grouting pressure and flow rate. Considering the change of the grouting position comprehensively, the grouting amount exceeds 80% of the design value and the grouting pressure reaches 2MPa, or the grouting pressure exceeds 3MPa. After the double pipe is lifted, repeat the above grouting process until the grouting is completed. The invention can prevent the occurrence of the phenomenon that the grouting pipe cannot be installed due to hole collapse; the compound injection of the two kinds of grout combines the advantages of the two kinds of grout to realize the water-stop curtain while satisfying the advantages of low permeability coefficient and high coagulation strength; Difficulty extubating due to reflux of serous fluid.

Description

Segment-retreat double-fluid composite grouting construction method for deep foundation pit in sandy pebble formation

technical field

The invention belongs to the technical field of foundation pit engineering, and relates to a construction method of segmented retreat double-liquid composite grouting for deep foundation pit grouting and waterproof reinforcement projects in sandy pebble formations.

Background technique

As far as the current situation of tunnel and underground engineering grouting in my country is concerned, for double-liquid grouting, double-pipe drill pipe grouting method and sleeve valve pipe grouting method are the construction methods that are currently used more and have better grouting effects. .

Existing double-pipe grouting construction generally adopts double-pipe drill pipe, and an in-pipe mixer is installed at the end. Clean water is used as the circulating fluid for drilling, and when the design depth or position is reached, the closed end point is used for lateral jet switching. Then use a grouting pump to inject the two kinds of slurry into the outer pipe and the inner pipe respectively, and the slurry is mixed in the end mixer of the double pipe, and sprayed in the horizontal direction through the filter screen to inject the slurry into the formation. The grouting adopts step-back grouting to achieve the effect of soil layer reinforcement. The disadvantage of this construction method is that when the drill pipe is used for grouting, there will inevitably be a gap between the drill pipe and the grouting hole, which will easily cause the grout to flow back during grouting, and it will be difficult to pull out the pipe for the grout with high consolidation strength, and the construction period will be longer .

Sleeve valve pipe retreat grouting is that after the grout is pressurized by the grouting pump, it enters the grouting pipe through the connecting pipe, gathers at the sleeve valve pipe grouting pipe section, and then passes through the PVC pipe drilled with grout holes (that is, the sleeve valve pipe ), under pressure, expand the rubber ring wrapped around the PVC pipe. When the pressure gradually increases to a certain level, the pressurized slurry will flow along the formation structure to fill, infiltrate, compact, and split, and the slurry will form a consolidated body in the formation, thereby increasing the strength of the formation and reducing the penetration of the formation. sexual purpose. The disadvantage of this construction method is that it is difficult to form a hole in the sand and pebble formation. After the drill pipe is pulled out, the hole is easy to collapse, and the sleeve valve cannot be installed.

Existing grouting projects usually use a single type of grout to inject, but the single type of grout usually has prominent shortcomings in comparison, such as the cement-water glass grout has a large permeability coefficient and poor injectability, and the acidic water glass grout condenses Body strength is low.

The present invention is proposed aiming at the above-mentioned deficiencies existing in the prior art.

Contents of the invention

In order to overcome the disadvantages of the existing double-pipe grouting method, such as grout backflow, difficulty in pulling out the pipe, and a long construction period, the retreating grouting of the sleeve valve pipe is easy to collapse the hole, the sleeve valve pipe cannot be installed, and the existence of a single type of grout is prominent. Disadvantages, the present invention provides a step-back two-liquid composite grouting construction method for deep foundation pits in sand and pebble formations.

In order to achieve the above-mentioned purpose, the step-back two-liquid composite grouting construction method of the deep foundation pit in the sand and pebble stratum of the present invention, the specific steps are:

1. Determine the grouting reinforcement plan

Determine the location of the grouting holes, the layout of the holes, the hole spacing, the hole row spacing and the drilling depth, and determine the model of the drilling rig and the model of the grouting pump. Among them, the double row is arranged in a plum blossom shape with holes to form a water-stop curtain of a certain thickness to achieve the purpose of water-stop reinforcement.

2. Field measurement and setting out

According to the measurement control network, the total station is used for the main positioning work, and then the laying-out team performs the laying-out work of the detailed dimensions according to the drawings.

3. Drilling

Aiming at the characteristics of difficult hole forming in sand and pebble strata, the imported RPD-130C full hydraulic drilling rig and Korean SH5000, SH6000, SH8000 drilling rigs are used to drill holes. High hole efficiency, fast and accurate positioning.

After the hole is formed, the double grouting pipe is lowered, and then the pipe puller is installed to pull out the drill pipe.

Before drilling, it is necessary to harden the ground within a width of 2m around the drilling hole. The hardening is made of C20 concrete with a thickness of 30cm.

4. Serum preparation

Liquid A: cement slurry, using ordinary Portland P.O42.5 cement, adding water, the water-cement ratio is 0.8-1.3.

Liquid B: water glass slurry, mixed with water glass and water at a concentration of 42Be' 1:1.

Solution C: Phosphoric acid solution, add water, and the concentration of the solution is 3%-8%.

A, B, and C liquids are stirred evenly, and the concentration of each slurry is adjusted according to the consolidation time required by the slurry. Wherein equal volume ratio A liquid and B liquid are mixed to form cement-water glass slurry, and equal volume ratio A liquid and B liquid are mixed to form acidic water glass slurry.

5. Grouting

(a) Whether the amount of grouting in the formation is appropriate is the embodiment of the reinforcement of the formation and the water-stopping effect. The method of injecting through holes is used to avoid the mutual influence of the grouting holes, and to make the post-injection holes supplement the first-injection holes to ensure The soil slurry spreads evenly. The cement-water glass slurry and the modified water glass slurry are double-liquid compositely injected, specifically: when grouting, the modified water glass slurry is injected first, and then the cement-water glass slurry is injected; the two types of slurry are mixed during the grouting process. , inject modified water glass slurry (liquid B and liquid C) into the inner row of grouting holes, and inject cement-water glass slurry (liquid A and liquid B) into the outer row; when grouting, observe the grouting pressure in real time, the pressure is relatively high Cement-water glass double liquid slurry (liquid A and liquid B) can be injected when the pressure is low, and modified water glass slurry (liquid B and liquid C) can be injected to quickly fill when the pressure is low;

The conversion of grout is considered comprehensively according to the change of grouting pressure, flow rate and grouting position, and the grout can be changed at any time through the valve switch of the grouting pipe.

(b) The grouting pressure is controlled at 1.5-3MPa, the grouting speed is 60L/min, the length of the grouting section is 5-10cm, and the grouting time is controlled at 20s-90s;

(c) When the grouting volume exceeds 80% of the design value and the grouting pressure reaches 2MPa, or the grouting pressure exceeds 3MPa, after the double pipe is lifted up, repeat the above grouting process until the grouting is completed.

Compared with the prior art, the present invention has the following advantages:

1. Lowering the grouting pipe first and then pulling out the drill pipe can prevent the phenomenon that the grouting pipe cannot be installed due to hole collapse.

2. The composite injection of the two kinds of grout can realize the advantages of the two kinds of grout in the grouting condensate, overcome the phenomenon of difficult extubation due to the backflow of the grout, and at the same time not affect the quality of the grouting.

3. Drilling and grouting are carried out synchronously and crosswise, which shortens the construction period.

Description of drawings

A more complete and better understanding of the invention, and many of its attendant advantages, will readily be learned by reference to the following detailed description when considered in conjunction with the accompanying drawings, but the accompanying drawings illustrated herein are intended to provide a further understanding of the invention and constitute A part of the present invention, the exemplary embodiment of the present invention and its description are used to explain the present invention, and do not constitute an improper limitation of the present invention, wherein:

Fig. 1 is a construction process flow chart of the present invention;

Fig. 2 is a layout diagram of the grouting system of the present invention.

Detailed ways

In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Figure 1 shows the construction process and operating points of the step-back two-liquid composite grouting method for deep foundation pits in sand and pebble formations of the present invention.

1) Determine the grouting reinforcement scheme

The grouting holes are distributed in the middle and outside of the retaining piles, in two rows, with a hole spacing of 900mm, and a quincunx pattern with a spacing of 600mm. Purpose: A total of 1,138 grouting holes are to be set up with φ89mm drill pipes. The drilling depth is from the current ground elevation (46.65m) to 0.5m below the conglomerate layer. The conglomerate layer elevation is 10.62m. The volume is 41572m. The grouting depth is 2m above the current water level of 21.89 to 0.5m below the conglomerate layer, and the grouting depth is 13.77m.

2) On-site measurement and setting out

According to the measurement control network, the total station is used for the main positioning work, and then the laying-out team performs the laying-out work of the detailed dimensions according to the drawings. Measuring instruments can only be used after passing the test.

3) drilling

Aiming at the characteristics of difficult hole forming in sand and pebble strata, the imported RPD-130C full hydraulic drilling rig and Korean SH5000, SH6000, SH8000 drilling rigs are used to drill holes. High hole efficiency, fast and accurate positioning.

This project adopts φ89 drill pipe for drilling, and the diameter of the hole is the same as that of the drill pipe. Before drilling, it is necessary to harden the ground within a width of 2m around the drilling hole. The hardening is made of C20 concrete with a thickness of 30cm.

Drilling Guarantee Measures:

1) Drilling should be carried out in strict accordance with the design parameters. The position and angle deviation of the drilling hole complies with the relevant specifications. If the drilling hole position on site cannot meet the design requirements due to objective conditions, it should be shifted and calculated to determine the parameters, and the hole should be repaired if necessary.

2) During the drilling construction process, it is necessary to stabilize the drilling rig and drill steadily. It requires experienced drillers to operate, and prevents inexperienced novices from rashly operating.

3) Check the mechanical equipment before going to work every shift, and it is strictly forbidden to operate the machine with a disease; at the same time, check the drilling tools, use drill pipes and drill bits with good quality and performance, and strictly prohibit the use of defective drilling tools.

After the hole is formed, the double grouting pipe with a diameter of 42mm is lowered. After completion, the pipe puller is installed to pull out the drill pipe.

4. Serum preparation

The setting time of the slurry is controlled to be within 30-90s for the cement-water glass slurry, and 2-10s for the modified water glass slurry.

Liquid A: cement slurry, using ordinary Portland P.O42.5 cement, the mix ratio is water: cement = 1:1.2.

Liquid B: water glass slurry, using Baumedo 42Be' water glass, the mixing ratio is water: water glass = 1:1.

Liquid C: quick-setting agent phosphoric acid solution, the mixing ratio is water: phosphoric acid = 1:0.05.

In order to meet the purpose of grouting consolidation, it is necessary to prepare grout in a certain order. For example, to dilute the cement slurry, add the required amount of water into the mixing tank according to each mixing body, start the mixer, and then add cement and stir for more than 3 minutes.

5. Grouting

Grouting pump test run

After confirming that all parts of the grouting system are connected correctly, start the grouting pump pressure water test to check the hydraulic pressure of the grouting pump, whether there is any grout leakage in the system pipeline, and whether the pipeline is unblocked.

Serous injection

After the system is ready, as shown in Figure 2, the well-proportioned liquid A is connected to the grouting pump 4 through the grout suction pipe 1, and the well-proportioned liquid B is connected to the grouting pump 4 through the grout suction pipe 2. Liquid C is connected to the grouting pump 4 through the grouting pipe 3 , and the grouting pump 4 delivers the grout to the grouting pipe 6 through the grouting pipe 5 .

First open the slurry suction pipe 2 and the slurry suction pipe 3, and close the slurry suction pipe 1 at the same time, and the slurry is pressed into the formation through the double pipes. After completing the designed grouting volume of 100L or when the grouting pressure suddenly increases, open the grouting pipe 1 and the grouting pipe 2, close the grouting pipe 3, the grout is pressed into the formation through the double pipes, and as the grouting pipe 6 goes up When the grouting pressure suddenly decreases, repeat the operation of opening the grout suction pipe 2, grout suction pipe 3, and closing the grout suction pipe 1. The method of injecting through holes is adopted, which not only avoids the mutual influence of the grouting holes, but also makes the post-grouting holes play the role of supplementing the first-grouting holes, so as to ensure that the soil grout spreads evenly.

Pressure and grouting volume control

Observe the grouting pressure through the pressure gauge 7, and check the pressure change with the increase of the grouting amount. Pressure control is adopted during the grouting process, the grouting pressure is controlled at 1.5-3MPa, and the grouting speed is 60L/min. When the grouting time reaches 15 minutes and the grouting pressure reaches 2.0Mpa, or the grouting pressure exceeds 3MPa, double pipe After lifting up 0.1m, continue grouting until the grouting is complete.

Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection should be based on the scope defined by the claims of the present invention. As mentioned above, although the Example of this invention was demonstrated in detail, it is obvious to those skilled in the art that many modifications can be made as long as the inventive point and effect of this invention are not substantially deviated. Therefore, all such modified examples are also included in the protection scope of the present invention.

Claims (2)

1. a sand-pebble layer deep foundation ditch segmentation retrusive biliquid combined casting job practices is characterized in that, may further comprise the steps:

1) determines the grouting and reinforcing scheme, determine the position of injected hole, arrangement, injected hole spacing, injected hole array pitch and the drilling depth of injected hole, determine rig model, grouting pump model; Wherein, position, injected hole hole is distributed in the middle of the fender post and the outside, totally two arranges, and injected hole adopts quincuncial arrangement;

2) in-site measurement unwrapping wire is mainly located work according to SURVEYING CONTROL NETWORK with total powerstation, is carried out the setting-out work of thin portion size again by drawing by unwrapping wire class;

3) boring behind the pore-forming, is transferred dual Grouting Pipe, and pipe extractor is installed then, extracts drilling rod;

4) slurries preparation,

A liquid: cement grout, adopt normal silicate P.O42.5 cement, add water, the water intaking gray scale is 0.8-1.3;

B liquid: the water glass slurries, adopt concentration 42Be ' water glass to mix with water 1:1;

C liquid: phosphoric acid solution, add water, getting solution concentration is 3%-8%;

A liquid, B liquid, C liquid stir respectively, the concentration that the consolidation time that requires according to slurries is regulated each slurries; Wherein equal-volume mixes back formation cement-sodium silicate slurries than A liquid with B liquid, and the B liquid of equal-volume ratio mixes formation modified water glass slurries with C liquid;

5) slip casting,

(a) mode of injecting every the hole is adopted in slip casting, with cement-sodium silicate slurries and the compound injection of modified water glass slurries biliquid, is specially: during slip casting, annotate modified water glass slurries, cementing again-water glass slurries earlier; Two kinds of slurries mixing slip castings in the slip casting process, interior row's injected hole injects modified water glass slurries (B liquid and C liquid), effluxes and then injects cement-sodium silicate slurries (A liquid and B liquid); Want the Real Time Observation grouting pressure during slip casting, but cementing-water glass biliquid slurry (A liquid and B liquid) when pressure is big, and pressure hour can be annotated modified water glass slurries (B liquid and C liquid) with rapid filling;

(b) grouting pressure control is that 60L/min, slip casting section length are to control at 20s-90s 5-10cm, slurry consolidation time at 1.5-3MPa, injection speed;

(c) when grouting amount surpass design load 80% simultaneously grouting pressure reach 2MPa, perhaps grouting pressure surpasses 3MPa, after carrying on the dual pipe, repeats above-mentioned slip casting process, finishes up to slip casting.

2. a kind of sand-pebble layer deep foundation ditch segmentation retrusive biliquid combined casting job practices according to claim 1, it is characterized in that, in the step 3), need before the boring to be hardened in ground in the wide 2m scope around the boring, C20 concrete, thickness 30cm are adopted in sclerosis.

Images