CN104005415A - Efficient grooving construction method for underground diaphragm wall in micro-weathered granite - Google Patents

Abstract

The invention provides a high-efficiency trough-forming construction method for an underground diaphragm wall in slightly weathered granite. The specific steps of the method include: the first step, geological survey at the construction site; the second step, determining the rock breaking method; the third step, determining Blasting parameters; the fourth step, forming a hole in the sand layer to the surface of the rock layer and unearthing; the fifth step, identifying the rock sample, and confirming that the drilled to the weathered granite; the sixth step, lowering the PVC pipe to protect the blasting wire; The seventh step is to form a hole in the rock formation to the design depth of 1m; the eighth step is to charge and blast. The invention overcomes the disadvantages and deficiencies of existing construction methods such as difficulty in construction or slow construction progress and poor trough-forming quality in overlying sandy soil micro-weathered granite, and realizes high-efficiency, high-precision, deep rock-socketed trough formation in slightly weathered granite Construction: the invention has good effect and fast groove forming speed.

Description

High-efficiency groove-forming construction method for underground diaphragm wall in slightly weathered granite

technical field

The invention relates to a construction technology in the fields of construction, water conservancy, transportation, environment and other underground engineering, in particular to an efficient groove-forming construction method for an underground continuous wall in slightly weathered granite.

Background technique

Major cities across the country are building urban underground railways and various underground spaces on a large scale. These underground space structures need to be constructed by excavating foundation pits, and underground diaphragm walls are required as temporary structures for retaining soil and water during excavation of foundation pits. Due to the different geological conditions and surrounding environments of each city, it is necessary to build underground diaphragm walls under various geological conditions. The construction technology of underground diaphragm wall has been widely used in my country's natural sedimentary sandy soil, cohesive soil and other soft soil strata. However, in South my country, there are generally slightly weathered rock layers such as limestone and granite under the sandy soil layer that is not too thick. There are still various technical difficulties in building an underground diaphragm wall in the upper soft and lower hard stratum of slightly weathered granite overlying the sandy soil layer. Traditional trough-forming machines and tools adapted to soft soil strata are difficult to grasp and excavate slightly weathered rock and soil in complex rock-soil layers that are soft at the top and hard at the bottom, resulting in the disadvantages of difficult or extremely slow construction of troughs, low construction efficiency, long construction period and high cost. situation.

After searching the existing literature, two related patent applications were found, the utility model patent "[application number is 201320455844.6], the name of the invention: an effective rock flushing device for underground diaphragm wall trough construction", and the invention patent "[ The application number is 201310322485.1], and the name of the invention is: an effective groove-forming construction method for underground diaphragm walls in slightly weathered limestone overlying sandy soil". Although these documents proposed solutions to technical problems such as the undulation of the underlying micro-weathered limestone rock surface and the inability to guarantee the verticality of grooves formed by traditional construction machinery, the construction method proposed in this document using a heavy hammer to impact and break limestone is not suitable for non-side Limestone with an unconfined compressive strength of less than 30 MPa is effective, while for slightly weathered granite with an unconfined compressive strength of more than 100 MPa, it is difficult for the hammer impact method proposed in the above literature to produce an efficient rock mass crushing effect. Especially for underground diaphragm walls with a rock-socketed depth of 3-8m, it is difficult to ensure the construction quality and construction period.

Contents of the invention

Aiming at the defects in the prior art, the object of the present invention is to provide a highly efficient trench-forming construction method for underground diaphragm walls in slightly weathered granite, which overcomes the problems of poor construction quality, long construction period and even inability to Shortcomings and deficiencies such as trough forming can be realized, and efficient trough forming construction in slightly weathered granite can be realized.

In order to achieve the above object, the present invention provides a kind of high-efficiency trough-forming construction method of underground diaphragm wall in slightly weathered granite, and the construction method is realized through the following steps:

The first step is the geological survey of the construction site, specifically:

Determine the rock surface properties and standard unconfined compressive strength distribution values of the micro-weathered granite within the rock-socketed depth range of the underground diaphragm wall through drilling and coring; on this basis, determine the underground diaphragm wall according to the designed buried depth of the diaphragm wall rock-socketed depth;

The second step is to determine the rock breaking method, specifically:

Because the traditional groove forming machine is difficult to excavate slightly weathered rock and soil in the complex rock and soil layer with soft top and hard bottom, and the impact of heavy hammer is only effective for limestone with unconfined compressive strength below 30MPa, so for unconfined compressive For micro-weathered granite with a strength above 100MPa, it is determined to use blasting to break the rock; since the construction of the underground diaphragm wall in the city requires little impact on the surrounding environment, in order to reduce the damage to the surrounding rock mass by blasting in the slightly weathered granite, a The flat profile surface is close to the design dimension of the underground diaphragm wall, so it is determined to adopt the micro-differential pre-splitting control blasting method;

The third step is to determine the blasting parameters, specifically:

1) According to the designed groove width of the underground diaphragm wall, the designed buried depth, the groove length of the primary blasting construction and the design principle of differential pre-splitting controlled blasting, first estimate the parameters of the blast hole, and then determine the blast hole through the third step 5). Hole parameters;

2) Since the rock to be blasted is slightly weathered granite, and the unconfined compressive strength distribution value of the slightly weathered granite is 100-180MPa, it is determined to choose 2# rock emulsion explosive, which has waterproof performance;

3) According to the micro-differential pre-splitting control blasting principle described in the second step, the detonator selects micro-secondary millisecond electric detonator;

4) According to the unconfined compressive strength distribution value of the rock and combined with the third step 5), determine the line charge density of the explosive; the line charge density ranges from 1.0 to 1.5kg/m; the line charge density can be calculated according to the following formula Dose density:

Q=Aa ^B σ ^C

In the formula: Q is the linear charge density;

a is the drilling distance;

σ is the unconfined compressive strength of rock;

A, B, and C are undetermined coefficients, which are determined by regression analysis after the third step 5) field test;

5) During the blasting construction, it is necessary to carry out the test blasting of the groove section. Select the test groove section in the construction site of the underground diaphragm wall, and select the blasting parameters in the third step 1) to 4) according to experience for blasting construction, and then blast the test groove section Drill and take core samples, and adjust the blasting parameters according to the sample fragmentation; repeat the above-mentioned test blasting steps of the groove section until the rock fragments can be captured by the groove forming machine, and determine the diameter of the drill holes, the distance between the drill holes, and the Coupling coefficient, hole depth, plugging length, linear charge density (A, B, C determined by regression analysis) and drilling spacing;

The fourth step is to form holes in the sand layer to the surface of the rock layer and unearth, specifically:

1) Level the site and remove ground obstacles;

2) Determine the drilling location according to the site plane and elevation control points, the design drawing of the underground diaphragm wall, the blasting parameters and the site conditions;

3) The down-the-hole drilling rig equipped with a sand layer drill bit drills at the determined drilling position, and at the same time protects the wall with a steel sleeve, and connects the steel sleeve while connecting the drill pipe until it reaches the moderately weathered granite rock face;

4) The auger earth taker takes out the soil in the borehole;

The fifth step is to identify the rock sample and determine that the drilled to medium weathered granite, specifically:

1) Replace the drill bit in the sand layer with a coring bit, extend down to the bottom of the borehole and drill down 0.5m, take out a moderately weathered rock sample of 0.5m and confirm that it is moderately weathered granite on site, and continue to drill down for 0.5m m, stop the core drilling after there is no change in the rock sample;

2) Take out the core bit;

The sixth step is to lower the PVC pipe to protect the blasting wire, specifically:

1) Insert the PVC pipe into the steel casing, and extend it while inserting; when the bottom of the PVC pipe reaches the bottom of the drill hole, inject water into the PVC pipe;

2) After the PVC pipe is extended to the ground, use a hacksaw to cut off the overlong part, and control the PVC pipe to be about 100mm higher than the ground;

3) Insert the grouting pipe to the bottom of the PVC pipe, and inject grout underwater to fix the PVC pipe to prevent water and soil in the sand layer from flowing into the PVC pipe and the rock formation drilling in the seventh step;

4) After the cement slurry is hardened, use a water pump to pump out all the water in the PVC pipe, and at the same time use a jack to pull out the steel casing;

The seventh step is to form holes in the rock formation to 1m below the designed buried depth, specifically:

1) Replace the core drill bit of the down-the-hole drilling rig with a rock formation drill bit, extend the drill bit down again to the surface of the cement slurry at the bottom of the PVC pipe, drill to 1m below the designed groove wall, and apply high-pressure wind while drilling to blow out the gravel powder;

2) Pull out the drill bit from the down-the-hole drilling rig, replace the tungsten-steel alloy drill bit with the soil layer drill bit, and drill in the next hole. Follow the above-mentioned steps to cycle until all the holes are drilled, and then withdraw the down-the-hole drilling rig;

The eighth step, charge blasting, specifically:

1) According to the designed charge amount and the drilling depth, tie the emulsion explosive charge and the lead wire to the bamboo pole and extend it down to the bottom of the drill hole to complete the single hole charge. After all the drill holes are charged, check charges and leads for each hole;

2) After all the drilling and charging are completed and the inspection is correct, use the detonator to connect all the lead wires and prepare for detonation;

3) Prepare well before blasting and start blasting;

4) After the blasting construction of the slot width is completed, the drilling and blasting of the next slot width is carried out;

The ninth step is the construction of the guide wall, and the construction of the groove is completed.

Preferably, in the first step 1):

The distribution value of the standard unconfined compressive strength is the distribution value of the soil compressive strength determined by applying axial pressure until the sample is destroyed under the unconfined condition in accordance with the geotechnical test regulations;

The rock face properties of the micro-weathered granite are obtained by taking cores from the boreholes as follows:

① Arrange the position and number of geological survey holes according to the size of the trough-forming area, respectively drill to the depth required for trough-forming construction to take out cores, and determine the number and spacing of drilled holes according to the size and scope of the trough-forming area. The two sides of the central axis of the underground diaphragm wall are staggered;

② Determine the rock surface depth and the thickness to be excavated in the trenching construction area by drilling and coring, and determine the relationship between the rock structural plane and the bending direction of the drilling hole or the earth's magnetic north direction. The rock structural plane has a certain shape and is ubiquitous According to different mechanical properties, the rock plane or curved surface with geological structure signs can be divided into five structural surface properties: extrusion surface, tension crack surface, torsion crack surface, compression torsion surface, and tension torsion surface;

③ Utilize the earth's gravity field, take the plumb line as the benchmark, and use the method of liquid level and pendent to measure the angle of the vertical plane in the inclined direction of the measuring point, that is, the top angle;

④ Utilize the earth's magnetic field, take the earth's magnetic meridian as the orientation reference, and use a magnetic compass to measure the angle between the tangent direction of a point on the borehole axis on the horizontal plane and the earth's magnetic north direction, that is, the azimuth;

⑤ Use the scanning electron microscope to conduct mineral micro-area testing, conduct trace element and isotope testing on the cores taken out, and analyze the mineral composition of the rock mass, so as to obtain the type, temperature, stress state and structural plane occurrence of the rock formation;

⑥ According to the top angle, azimuth angle, mineral micro-region test results, the fabric type or interference color contrast of the rock subjected to stress, and the stress mineral characteristics generated, the stress nature of the structural plane is inferred, and the rock surface properties of the rock are determined.

Preferably, in the first step 2), the permeability index of the dimensionless water is calculated by the following formula:

${\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}$

In the formula: B _q = dimensionless pore water pressure coefficient, Q _t = dimensionless cone tip resistance, calculated by the following two formulas:

${\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}}$

${\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}}{{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}$

where: u _a = absolute pore pressure,

u _s = initial static pore water pressure,

q _t = modified cone tip resistance,

σ _v0 = initial total vertical stress.

Preferably, in the second step, the micro-differential pre-splitting control blasting method is to drill a row of holes and charge along the periphery of the designed excavation line in addition to the normal drilling and charge of the design in the excavation area; The hole is blasted first, and the excavation area is blasted later; the peripheral drilling of the blasting first produces a 1-4cm crack; when the excavation area of the blasting is blasted later, the energy of the shock wave is weakened by the peripheral seams, which can reduce the impact on the surrounding seams. Blast impact in the zone, which smooths the excavation boundary on the design line.

Preferably, in the third step 1), the blasthole parameters include borehole diameter, borehole spacing, uncoupling coefficient, hole depth and plugging length, wherein:

The borehole diameter is determined according to the designed slot width and the slot length of the primary blasting construction. When the designed slot width is 600-1000mm and the slot length of the primary blasting construction is 12m, the range of the drilling diameter is 50-100mm. 150mm; For projects with high quality requirements, use small drilling holes;

The borehole spacing is 5 to 7 times the borehole diameter. When the borehole diameter is greater than 100mm, take a small value, and when it is less than 100mm, take a large value. For weak and broken rocks, take a small value, and for hard rocks, take a large value. High quality requirements Take a small value for those with low requirements, and take a large value for those with low requirements;

The non-coupling coefficient is the ratio of the inner diameter of the blast hole to the diameter of the cartridge. For the designed groove width of 600-1000 mm, the non-coupling coefficient of the underground diaphragm wall is 1.5-2.5. The gap between them is large, and the damage to the hole wall after blasting is small, otherwise the damage to the hole wall is large;

The hole depth is determined according to the design buried depth of the underground diaphragm wall, and the hole depth is taken from the ground to 0.5m to 1.5m below the designed buried depth of the underground diaphragm wall;

The plugging length is 12 to 20 times the diameter of the blast hole.

Preferably, in the third step 3), the differential millisecond electric detonator is a delay electric detonator with a segment interval of more than ten milliseconds to hundreds of milliseconds.

Preferably, in the fourth step 3):

The sand layer drill bit is a diamond eccentric drill bit, the diameter of the drill bit is 5-10 mm larger than the diameter of the blasting hole in the rock layer, and is used for drilling in the sand layer;

The down-the-hole drilling rig is a drilling equipment that uses a drill rod to drive a pneumatic impactor and a drill bit to rotate and break rock; during the rock drilling process, the impactor is submerged into the hole to reduce the energy loss caused by the impact energy transmitted by the drill rod , so as to reduce the influence of hole depth on rock drilling efficiency; for slightly weathered granite with unconfined compressive strength distribution value of 100-180MPa, higher rock drilling speed can be obtained;

The drill rod is a circular percussion drill rod; the upper end has a tapered external thread and the lower end has a tapered internal thread for connecting the drill bit; both ends of the drill rod are provided with a wrench cut and an annular groove for fishing. Unscrew;

The steel sleeve is a thin-walled steel cylinder with a diameter 5-10 mm smaller than that of the diamond eccentric drill bit, to prevent the drill hole from collapsing in the sand; the upper end has a tapered external thread, and the lower end has a tapered internal thread for connection; the steel sleeve Both ends of the barrel have wrench cutouts and annular grooves for removal.

Preferably, in the fourth step 4), the auger soil removal machine is a soil removal device equipped with a long helical drill bit; the long helical drill bit is inserted into the borehole, and the soil in the hole is taken out by rotating blades; The outer diameter of the helical bit is smaller than the inner diameter of the steel sleeve.

Preferably, in the fifth step 1), the core bit is a hollow diamond core bit, and the diameter of the bit is the same as that of the bit in the sand layer.

Preferably, in the sixth step 1),

The diameter of the PVC pipe is smaller than that of the steel sleeve, and the two PVC pipes are overlapped by a joint PVC pipe whose inner diameter is equal to its outer diameter, and are bonded firmly with glue;

The amount of water injection can be roughly estimated according to the following formula:

$\mathrm{<span\; class="notranslate">\; G</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&pi;kdht</span>}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; \&pi;d</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}$

In the formula: G = water injection volume,

k = the average value of the permeability coefficient of the sand layer obtained in the first step 2),

d=the diameter of the steel sleeve mentioned in the fourth step,

h=height difference from water injection level to medium weathered granite rock surface,

t = the total time from the start of water injection to the end of step 3) grout injection.

Preferably, in the sixth step 3), the water-cement mass ratio of the cement slurry is 0.8:1, the cement slurry is mixed with 32.5 grade ordinary Portland cement, the grouting pressure is controlled at 0.1-0.4MPa, and the grouting speed It is 3-7L/min; the amount of grouting is the amount used to seal the bottom of the PVC pipe to prevent the hole from collapsing when the steel casing is pulled out. It can be roughly estimated according to the diameter of the steel casing and the diameter of the PVC pipe, and according to the rock fracture during drilling. Adjust the actual grouting volume.

Preferably, in the sixth step 4), the water pump is a machine that uses a power machine to transmit and discharge water.

Preferably, in the seventh step 1), the rock formation drill bit is a tungsten steel alloy drill bit, and the diameter of the drill bit is equal to the product of the cartridge diameter and the uncoupling coefficient, which is used for drilling in the rock formation; the high-pressure air is provided by a wind compressor .

Preferably, in the eighth step 3), the preparatory work before the blasting is to add a punching hammer to the steel plate covering the top surface of the blasting area to prevent damage to the surrounding protection caused by individual flying stone mud; strict safety precautions are implemented during blasting ; During the blasting, all personnel are evacuated to a safe place before detonating, and the blasting warning distance is not less than 100m.

Preferably, in the ninth step 1), the construction of the guide wall specifically includes: excavating a groove for the guide wall, binding and lowering the reinforcement cage, then setting up a formwork, and pouring concrete after the reinforcement cage and the formwork are accepted; The wall construction is carried out in sections, and the section length is determined and controlled within the range of 30-50m according to the formwork length and specifications.

Preferably, in the ninth step 2), the mud is chemical mud, and the slurry preparation material is water, bentonite and sodium carbonate, and water, bentonite and sodium carbonate of different mass ratios are used for penetration tests, and the permeability coefficient is recorded as Step 2) The ratio when the permeability coefficient of the sand layer is measured to be 1% is the construction ratio; during operation, the height of the mud liquid level is kept below the ground level by 0.5m to form a sufficient mud column pressure to balance the underground The lateral earth pressure within the diaphragm wall, that is, the mud column pressure (σ _n ) is greater than or equal to the lateral earth pressure (σ _t ), and mud is added to the hole at any time.

More preferably, the penetration test is the test method described in the "Geotechnical Test Regulations" (SL237-1999) penetration test SL237-014-1999.

More preferably, the lateral earth pressure refers to the lateral earth pressure generated by the soil within the design depth of the underground diaphragm wall on the mud column, which can be estimated according to the following formula:

σ _h =K ₀ σ _v0

where σ _h = lateral earth pressure, σ _v0 = initial total vertical stress, K ₀ = coefficient of lateral earth pressure, calculated by the following formula:

K ₀ =1-sinθ

In the formula, θ = internal friction angle of the sandy soil layer, which is determined by the triaxial compression test SL237-017-1999 in the "Geotechnical Test Regulations" (SL237-1999).

More preferably, the mud column pressure can be calculated according to the following formula:

σ _n =γ _n h _n

where: σ _n = mud column pressure,

γ _n = mud weight,

h _n = buried depth of the mud column, 0.5m below the designed buried depth.

Preferably, in the ninth step 3), the hammer body of the heavy hammer is a cross circular truncated body, the bottom of the hammer is provided with alloy teeth, and the alloy teeth are distributed in a cross snowflake shape; the detailed structure of the heavy hammer can be found in the utility model patent "[Application No. 201320455844.6], title of invention: an effective rock flushing device for underground diaphragm wall trenching construction".

Compared with the prior art, the present invention has the following beneficial effects:

The construction method of the present invention overcomes the disadvantages and deficiencies of existing construction methods such as difficult construction or slow construction progress and poor groove quality in the overlying sandy slightly weathered granite, and realizes high-efficiency, high-precision, deep rock-socketing in the slightly weathered granite trough forming construction; the invention has good effect, and the drilling success rate is 100%; the trough forming speed is fast, and the engineering period is reduced to one-tenth of the traditional heavy hammer ramming trough forming method.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

Fig. 1 is the position of the blast hole and the schematic diagram of charge of underground diaphragm wall groove wall of the present invention;

Fig. 2 is a schematic diagram of the processing of an expanded drug pack of the present invention;

Fig. 3 is a schematic diagram of the trenching construction steps in the overlying sandy slightly weathered granite of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

This embodiment provides an efficient trench-forming construction method for an underground diaphragm wall in slightly weathered granite, which is used in a site where a subway station is proposed to be built. The total length of the station outsourcing is 236.4m, and the soil layer in the area is a breeze covered with sandy soil. It is planned to use drilling and blasting to construct trenches for the underground diaphragm wall, with a trench depth of 18m and a design width of 800mm; the construction steps are shown in Figure 3.

The concrete construction steps of construction method described in the present embodiment are as follows:

Step 1. Construction site geological survey, specifically:

Drilling holes are arranged every 50m, drilled to a depth of 22m, and then the core is taken out. According to the drilling bending parameters, the buried depth of the rock surface in the area to be constructed is determined to be 11-15m, and the depth of the groove into the rock is 3-7m. The surface properties are complex inclination direction, the inclination angle is 10°-25°, and the unconfined compressive strength distribution value of the slightly weathered granite layer is between 100-180MPa.

Use the static sounding method with pore water pressure to determine the properties of the sandy soil layer in the proposed foundation pit area. The test depth of the static sounding sounding is from the surface to the weathered granite rock surface, and an inspection hole is arranged every 50m along the longitudinal direction of the foundation pit. And the number is not less than 3; use static contact to detect the relationship curve between the penetration resistance of the soil and the pore water pressure and depth, and draw the ratio of the pore water pressure to the penetration resistance as the horizontal axis, and the penetration resistance The ratio of the initial stratum stress to the vertical axis is the relationship diagram, and the diagram is divided into several different soil characteristic areas to represent different soil types; the data of the measured static penetration curve is marked on the diagram to judge the site soil The type of layer, and determine the permeability coefficient of the sand layer according to the following formula:

$\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}}\mathrm{<span\; class="notranslate">\; Ua</span>}{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}$

In the formula: k = permeability coefficient,

K _D = Dimensionless permeability coefficient of water,

U=cone penetration rate,

a = the radius of the cross-sectional circular surface of the piezostatic penetration probe,

γ _w = soil bulk density,

σ _v0 = initial total vertical stress;

In this embodiment, the static penetration method with pore water pressure is used to obtain the soil layer division information of the shallow soil including the tunnel. ^4ml ), alluvium-diluvium (Q ^4al+pl ), granite and migmatite residual layer (Q ^el ), underlying Yanshanian granite (γ ⁵³ ), Caledonian migmatite (M ^γ3 ); The permeability coefficients of sandy soil layer are: 1.56, 1.86, 2.16, 1.99m/d.

Step 2. Determine the use of differential pre-splitting control blasting method to break rocks and construct underground diaphragm walls

In this embodiment, the micro-differential pre-splitting control blasting method is to drill a row of holes along the periphery of the designed excavation line and charge the explosives in addition to the normal drilling and charging in the excavation area according to the design; Explosion, blasting after the excavation area; the peripheral drilling of the blasting first produces a 1-4cm crack; when the excavation area of the post-explosion is blasted, the energy of the shock wave is weakened by the peripheral seam, which can reduce the impact on the area outside the peripheral seam Blast impact, which smooths the excavation boundary on the design line.

Step 3, determine the blasting parameters, specifically:

According to the slightly weathered granite 5m, the length of the groove width of the blasting construction is 12m, select the test section in the construction site for blasting construction, and determine the blasting parameters: the diameter of the sand layer drilling hole is 150mm, the rock formation drilling diameter is 76mm, and the drilling distance is 650mm , the non-coupling coefficient is 1.8, the drilling depth is 19m, and the plugging length of the interval charging section is 0.6m. 2# rock emulsion explosive is selected, and two instantaneous detonators are selected for field test blasting. The relevant parameters are A=0.7, B=0.8, C =0.9, the unit consumption of explosives is 1.3kg/m. Figure 1 is a schematic diagram of the position of the blast hole and charge of the trench wall of the underground diaphragm wall in this embodiment, and Figure 2 is a schematic diagram of the processing of the charge bag in this embodiment.

Step 4, forming holes in the sand layer to the surface of the rock layer and unearthed, specifically:

Level the site and remove ground obstacles; determine the drilling position according to the site plane and elevation control points, underground diaphragm wall design drawings, blasting parameters and site conditions; as shown in Figure 3 (1), the DTH drilling rig is installed with a diamond The eccentric drill bit is equipped with a steel casing protection wall outside the drill bit. The down-the-hole drilling machine drills at the determined drilling position, and connects long casings while drilling until it drills into the weathered granite rock surface; as shown in Figure 3 (2) As shown, take out the soil in the borehole with an auger with an outer diameter of 130mm.

In this embodiment, the drill rod is a circular percussion drill rod with a tapered external thread at the upper end and a tapered internal thread at the lower end. The two ends of the drill rod are provided with a wrench notch and an annular groove for fishing to facilitate screwing. Unload.

In this embodiment, the steel sleeve is a thin-walled steel cylinder with a diameter of 146mm; the upper end has a tapered external thread, the lower end has a tapered internal thread, and both ends of the steel sleeve are provided with wrench cuts and annular grooves for removal.

Step 5. Identify the rock sample and determine that the drilled to medium weathered granite, specifically:

Replace the drill bit in the sand layer with a hollow diamond core bit with a diameter of 110mm for coring, extend down to the bottom of the borehole and drill down 0.5m, take out 0.5m of moderately weathered rock samples and confirm the identification of the rock samples by the on-site construction workers , continue to take coring for 0.5m, and stop coring drilling after the rock sample has no change; take out the coring bit.

Step 6. Lower the PVC pipe to protect the blasting wire, specifically:

As shown in Figure 3 (3), insert the PVC pipe into the steel casing and extend it while inserting it. When the bottom of the PVC pipe reaches the bottom of the drill hole, inject water into the PVC pipe for 30 minutes; the PVC pipe is extended to the ground Finally, cut off the overlong part with a hacksaw, and control the PVC pipe to be about 100mm higher than the ground; as shown in Figure 3 (4), insert the grouting pipe to the bottom of the PVC pipe, and inject grout underwater to fix the PVC pipe. Prevent the water and soil in the sand layer from flowing into the PVC pipe and the rock formation drilling in the seventh step; as shown in Figure 3 (5), after the cement slurry hardens, use a pump to pump out all the water in the PVC pipe, and at the same time use a jack to lift the steel sleeve The tube is pulled out.

In the present embodiment, the outer diameter of the PVC pipe is 90mm, and the bottom of the pipe is blocked with a plug with an inner diameter of 90mm. The length of each PVC pipe is 4m. The glue sticks firmly.

In this embodiment, the water injection volume is 350L.

In this example, the water-cement mass ratio of the cement slurry is 0.8:1, the cement slurry is mixed with 32.5 grade ordinary Portland cement, the grouting pressure is controlled at 0.3MPa, and the grouting speed is 5L/min. Slurry time is 10min.

Step 7. Form holes in the rock formation to 1m below the designed buried depth, specifically:

As shown in Figure 3 (6), replace the core drill bit of the down-the-hole drilling rig with a tungsten steel alloy drill bit with a diameter of 76mm, extend the drill bit down to the surface of the cement slurry at the bottom of the PVC pipe, and drill to 1m below the designed groove wall, while drilling While applying high-pressure air to blow out the gravel powder; as shown in Figure 3 (7), the down-the-hole drilling rig pulls out the drill bit, replaces the tungsten steel alloy drill bit with a diamond eccentric drill bit, and drills in the next hole. The down-the-hole drilling rig was withdrawn until the construction of 22 drilling holes was completed.

Step eight, charge blasting, as shown in Figure 3 (8), specifically:

According to the designed charge amount and drilling depth, tie the processed charge pack and lead wire to the bamboo pole and extend it down to the bottom of the drilled hole to complete the single hole charge. After all the drill holes are charged, check each charge and lead wires for each hole; after all the holes are drilled and charged, and after the inspection is correct, connect all the lead wires with the detonator and prepare for detonation; do the preparation work before blasting, and add a punching hammer to the top surface of the blasting area covering the steel plate, In order to prevent individual flying rocks and mud from causing damage to the surrounding protection; set up a safety warning line, and evacuate all personnel to a safe place; connect all lead wires with a detonator, and the blasting engineer will start the blasting; after the blasting construction of the slot width is completed, proceed to the next Drilling and blasting of a slot width.

In the present embodiment, the charge pack is 2# rock emulsion explosive, the charge roll diameter is 60mm, the single-hole charge is 4kg, and the amount of a pair of underground diaphragm walls is 56kg; 56 non-electric detonators are used; the plugging material is coarse sand .

In this embodiment, the blast hole is detonated with positive charges, and the detonator is selected from two instantaneous detonators, which belong to two non-electric detonation networks respectively, and detonate after the two sets of networks are connected in parallel.

Step 9: Construction of the guide wall, as shown in Figure 3 (9); after the hole-forming blasting of the underground diaphragm wall within a certain range is completed, the guide wall is constructed, specifically:

As shown in Figure 3 (10), under the condition of the mud retaining wall, use the slotting machine to grab the upper sand and broken rock; as shown in Figure 3 (11), under the condition of the mud retaining wall, use the heavy hammer to punch 1. Hammering the rock surface, immediately after the completion of each hammering footage construction, dig out the broken rock with a groove forming machine; use a square hammer to clean the remaining protruding rock stems on the groove wall, and connect the holes to form grooves; as shown in Figure 3 (12), use The trough forming machine grabs the broken rock at the bottom of the trough, and the trough forming construction is completed.

In this embodiment, the guide wall is 200mm thick, 100mm outside, and 1.5m deep; it is constructed in sections by cast-in-place concrete, and the length of each section is 50m.

In this embodiment, the mud mixing material and its ratio are: water: bentonite: sodium carbonate = 1:0.04:0.0002.

In this embodiment, the mass of the heavy hammer is 3t, the center of the shaft is hollow, and the hole diameter of the shaft center is 120mm; Silicon steel alloy teeth 3 are arranged on the top, and the silicon steel alloy teeth 3 are distributed in a cross snowflake shape, and the adjacent silicon steel alloy teeth 3 are connected by steel bars 2; the lifting height of the hammer from the rock surface to be washed is 3m, and the hammering footage is 400mm; Immediately after the construction of each footage is completed, the broken rock is dug out with a slotting machine; the construction sequence of this step is from both sides to the middle, first the main punching and then the auxiliary punching.

In this embodiment, the hammer face of the square hammer is 1600 mm long and 800 mm wide, and silicon steel alloy teeth with a thickness of 60 mm and a height of 400 mm are welded around the hammer face.

The construction method of the present invention overcomes the disadvantages and deficiencies of existing construction methods such as difficult construction or slow construction progress and poor groove quality in the overlying sandy slightly weathered granite, and realizes high-efficiency, high-precision, deep rock-socketing in the slightly weathered granite trough forming construction; the invention has good effect, and the drilling success rate is 100%; the trough forming speed is fast, and the engineering period is reduced to one-tenth of the traditional heavy hammer ramming trough forming method.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (10)

1. a kind of high-efficiency trenching construction method of underground diaphragm wall in slightly weathered granite, it is characterized in that, described construction method realizes by following steps: The first step, geological survey at the construction site: determine the rock surface properties and the distribution value of the standard unconfined compressive strength of the micro-weathered granite within the depth range of the rock-socketed underground diaphragm wall through drilling and coring; on this basis, according to the underground continuous wall The designed buried depth of the wall determines the rock-socketed depth of the underground diaphragm wall; The second step is to determine the rock-breaking method: for slightly weathered granite with an unconfined compressive strength of 100 MPa or more, the micro-differential pre-splitting control blasting method is used; The third step is to determine the blasting parameters: 1) According to the designed groove width of the underground diaphragm wall, the designed buried depth, the groove length of the primary blasting construction and the design principle of differential pre-splitting controlled blasting, first estimate the parameters of the blast hole, and then determine the blast hole through the third step 5). Hole parameters; 2) The unconfined compressive strength distribution value of slightly weathered granite is 100-180MPa, and it is determined to use 2# rock emulsion explosive, which has waterproof performance; 3) According to the micro-differential pre-splitting control blasting method described in the second step, the detonator selects a micro-second electric detonator, that is, an electric detonator whose interval is more than ten milliseconds to hundreds of milliseconds; 4) According to the unconfined compressive strength distribution value of the rock and combined with the third step 5), determine the line charge density of the explosive; the line charge density ranges from 1.0 to 1.5kg/m; calculate the line charge according to the following formula Quantity density: Q=Aa ^B σ ^C ; where: Q is the linear charge density; a is the drilling distance; σ is the unconfined compressive strength of rock; A, B, and C are undetermined coefficients. ) to determine the method of regression analysis after field test; 5) During the blasting construction, it is necessary to carry out the test blasting of the groove section. Select the test groove section in the construction site of the underground diaphragm wall, and select the blasting parameters in the third step 1) to 4) according to experience for blasting construction, and then blast the test groove section Drill and take core samples, and adjust the blasting parameters according to the sample fragmentation; repeat the above-mentioned test blasting steps of the groove section until the rock fragments can be captured by the groove forming machine, and determine the diameter of the drill holes, the distance between the drill holes, and the Coupling coefficient, hole depth, plugging length, linear charge density and drilling spacing; The fourth step is to form holes in the sand layer to the surface of the rock layer and unearth: 1) Level the site and remove ground obstacles; 2) Determine the drilling location according to the site plane and elevation control points, the design drawing of the underground diaphragm wall, the blasting parameters and the site conditions; 3) The down-the-hole drilling rig equipped with a sand layer drill bit drills at the determined drilling position, and at the same time protects the wall with a steel sleeve, and connects the steel sleeve while connecting the drill pipe until it reaches the moderately weathered granite rock face; 4) The auger earth taker takes out the soil in the borehole; The fifth step is to identify the rock sample and determine that the drilled to medium weathered granite: 1) Replace the drill bit in the sand layer with a core bit, extend down to the bottom of the borehole and drill down 0.5m, take out 0.5m of moderately weathered rock samples and confirm that it is moderately weathered granite, and continue to take 0.5m down the core , when there is no change in the rock sample, stop the core drilling; 2) Take out the core bit; The sixth step is to lower the PVC pipe to protect the blasting wire: 1) Insert the PVC pipe into the steel casing, and extend it while inserting; when the bottom of the PVC pipe reaches the bottom of the drill hole, inject water into the PVC pipe; 2) After the PVC pipe is extended to the ground, use a hacksaw to cut off the overlong part, and control the PVC pipe to be 100mm higher than the ground; 3) Insert the grouting pipe to the bottom of the PVC pipe, and inject grout underwater to fix the PVC pipe to prevent water and soil in the sand layer from flowing into the PVC pipe and the rock formation drilling in the seventh step; 4) After the cement slurry is hardened, use a water pump to pump out all the water in the PVC pipe, and at the same time use a jack to pull out the steel casing; The seventh step is to form a hole in the rock formation to 1m below the designed buried depth: 1) Replace the core drill bit of the down-the-hole drilling rig with a rock formation drill bit, extend the drill bit down again to the surface of the cement slurry at the bottom of the PVC pipe, drill to 1m below the designed groove wall, and apply high-pressure wind while drilling to blow out the gravel powder; 2) Pull out the drill bit from the down-the-hole drilling rig, replace the tungsten-steel alloy drill bit with the soil layer drill bit, and drill in the next hole. Follow the above-mentioned steps to cycle until all the holes are drilled, and then withdraw the down-the-hole drilling rig; The eighth step, charge blasting: 1) According to the designed charge amount and the drilling depth, tie the emulsion explosive charge and the lead wire to the bamboo pole and extend it down to the bottom of the drill hole to complete the single hole charge. After all the drill holes are charged, check charges and leads for each hole; 2) After all the drilling and charging are completed and the inspection is correct, use the detonator to connect all the lead wires and prepare for detonation; 3) Prepare well before blasting and start blasting; 4) After the blasting construction of the slot width is completed, the drilling and blasting of the next slot width is carried out; The ninth step is the construction of the guide wall, and the construction of the groove is completed. 2. the efficient groove-forming construction method of underground diaphragm wall in a kind of slightly weathered granite according to claim 1, is characterized in that, in the first step 1): the distribution value of described standard unconfined compressive strength follows Geotechnical test procedures, under unconfined conditions, apply axial pressure until the specimen fails to determine the soil compressive strength distribution value; The rock face properties of the micro-weathered granite are obtained by taking cores from the boreholes as follows: ① Arrange the position and number of geological survey holes according to the size of the trough-forming area, respectively drill to the depth required for trough-forming construction to take out cores, and determine the number and spacing of drilled holes according to the size and scope of the trough-forming area. The two sides of the central axis of the underground diaphragm wall are staggered; ② Determine the rock surface depth and the thickness to be excavated in the trenching construction area by drilling and coring, and determine the relationship between the rock structural plane and the bending direction of the drilling hole or the earth's magnetic north direction. The rock structural plane has a certain shape and is ubiquitous According to different mechanical properties, the rock plane or curved surface with geological structure signs can be divided into five structural surface properties: extrusion surface, tension crack surface, torsion crack surface, compression torsion surface, and tension torsion surface; ③ Utilize the earth's gravity field, take the plumb line as the benchmark, and use the method of liquid level and pendent to measure the angle of the vertical plane in the inclined direction of the measuring point, that is, the top angle; ④ Utilize the earth's magnetic field, take the earth's magnetic meridian as the orientation reference, and use a magnetic compass to measure the angle between the tangent direction of a point on the borehole axis on the horizontal plane and the earth's magnetic north direction, that is, the azimuth; ⑤ Use the scanning electron microscope to conduct mineral micro-area testing, conduct trace element and isotope testing on the cores taken out, and analyze the mineral composition of the rock mass, so as to obtain the type, temperature, stress state and structural plane occurrence of the rock formation; ⑥ According to the top angle, azimuth angle, mineral micro-region test results, the fabric type or interference color contrast of the rock subjected to stress, and the stress mineral characteristics generated, the stress nature of the structural plane is inferred, and the rock surface properties of the rock are determined. 3. the efficient trough-forming construction method of underground diaphragm wall in a kind of slightly weathered granite according to claim 1, is characterized in that, in the 3rd step 1), described blasthole parameter comprises borehole diameter, borehole spacing, Uncoupling coefficient, hole depth and plugging length, wherein: the borehole diameter is determined according to the designed slot width and the slot length of one blasting construction, when the designed slot width is 600-1000 mm, the slot length of one blasting construction When the diameter is 12m, the drilling diameter ranges from 50 to 150mm; for projects with high quality requirements, use small drilling holes; The borehole spacing is 5 to 7 times the borehole diameter. When the borehole diameter is greater than 100mm, take a small value, and when it is less than 100mm, take a large value. For weak and broken rocks, take a small value, and for hard rocks, take a large value. High quality requirements Take a small value for those with low requirements, and take a large value for those with low requirements; The non-coupling coefficient is the ratio of the inner diameter of the blast hole to the diameter of the cartridge. For the designed groove width of 600-1000 mm, the non-coupling coefficient of the underground diaphragm wall is 1.5-2.5. The gap between them is large, and the damage to the hole wall after blasting is small, otherwise the damage to the hole wall is large; The hole depth is determined according to the design buried depth of the underground diaphragm wall, and the hole depth is taken from the ground to 0.5m to 1.5m below the designed buried depth of the underground diaphragm wall; The plugging length is 12 to 20 times the diameter of the blast hole. 4. the efficient trough-forming construction method of underground diaphragm wall in a kind of slightly weathered granite according to claim 1, is characterized in that, in described 4th step 3): described sand layer drill bit is diamond eccentric drill bit, drill bit The diameter is 5-10mm larger than the diameter of the blasting hole in the rock formation, and it is used for drilling in the sandy soil layer; The down-the-hole drilling rig is a drilling equipment that uses a drill rod to drive a pneumatic impactor and a drill bit to rotate and break rocks; The drill rod is a circular percussion drill rod; the upper end has a tapered external thread and the lower end has a tapered internal thread for connecting the drill bit; both ends of the drill rod are provided with a wrench cut and an annular groove for fishing. Unscrew; The steel sleeve is a thin-walled steel cylinder with a diameter 5-10 mm smaller than that of the diamond eccentric drill bit, to prevent the drill hole from collapsing in the sand; the upper end has a tapered external thread, and the lower end has a tapered internal thread for connection; the steel sleeve Both ends of the barrel have wrench cutouts and annular grooves for removal. 5. The efficient trough-forming construction method of underground diaphragm wall in a kind of slightly weathered granite according to claim 1, is characterized in that, in described fourth step 4), described spiral earth-moving machine is installed with long spiral Soil removal equipment for the drill bit; insert the long helical drill bit into the borehole, and take out the soil in the hole through the rotating blade; the outer diameter of the long helical drill bit is smaller than the inner diameter of the steel sleeve. 6. the efficient trough-forming construction method of underground diaphragm wall in a kind of slightly weathered granite according to claim 1, is characterized in that, in the 5th step 1), described coring bit is hollow diamond coring bit, and drill bit diameter It is the same as the drill bit in the sand layer. 7. the efficient trough-forming construction method of underground diaphragm wall in a kind of slightly weathered granite according to claim 1, is characterized in that, in the 6th step 1), the diameter of described PVC pipe is smaller than steel sleeve pipe, two The PVC pipe is lapped and lengthened by a joint PVC pipe whose inner diameter is equal to its outer diameter, and is firmly pasted with glue. 8. the efficient trough-forming construction method of underground diaphragm wall in a kind of slightly weathered granite according to claim 1, is characterized in that, in the 6th step 3), described cement slurry water-cement mass ratio is 0.8:1, The cement slurry is mixed with 32.5 grade ordinary Portland cement, the grouting pressure is controlled at 0.1-0.4MPa, and the grouting speed is 3-7L/min; The amount of hole collapse can be roughly estimated according to the diameter of the steel casing and the diameter of the PVC pipe, and the actual grouting amount should be adjusted according to the rock fracture during drilling. 9. The efficient trough-forming construction method of underground diaphragm wall in a kind of slightly weathered granite according to claim 1, it is characterized in that, in the 7th step 1): the rock formation drill bit is a tungsten steel alloy drill bit, and the drill bit diameter It is equal to the product of the diameter of the charge pack and the uncoupling coefficient, and is used for rock formation drilling; the high-pressure air is provided by an air compressor. 10. The efficient groove-forming construction method of underground diaphragm wall in a kind of slightly weathered granite according to claim 1, characterized in that, in the eighth step 3), the preparatory work before the blasting is to cover the top surface of the blasting area Steel plates and punching hammers are used to prevent individual flying rocks and mud from causing damage to surrounding protection; strict safety precautions are implemented during blasting; blasting can only be initiated after all personnel are evacuated to a safe place during blasting, and the blasting warning distance is not less than 100m.