Construction method for low influence of pile group on hard rock blasting of deep foundation pit

Abstract

The invention discloses a construction method for pile group low-influence deep foundation pit hard rock blasting, which comprises a groove broaching area, a non-groove broaching area, a pile adjacent area, micro-blasting holes, main blasting holes and energy eliminating and gathering iron balls, the groove broaching area mainly provides a free face for the non-groove broaching area to facilitate blasting, and the micro-blasting holes and buffer holes are formed in the periphery of the pile adjacent area to facilitate blasting. And the influence of extrusion and vibration of the uplift pile in the blasting process is controlled. Peripheral micro blasting holes and main blasting holes are distributed in the groove broaching area, and a peripheral presplitting and middle layered blasting method is adopted; main blasting holes are distributed in a non-broaching groove area, deep hole millisecond loosening is adopted to control blasting, buffer holes are formed in the outer side of a pile adjacent area, and the influence of controlled blasting on an engineering pile is reduced; micro-explosion holes are distributed in the adjacent pile area and are formed in the inner sides of the buffer holes. Through the combined blasting construction method, the influence on a pile foundation in the blasting process is effectively reduced, the protection safety coefficient of a finished engineering pile is improved, and the quality and the qualification rate of a pile body are ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of municipal water engineering, and in particular relates to a construction method for low-impact deep foundation pit hard rock blasting by pile groups. Background Art

[0002] In the construction of municipal water projects, in order to improve the current water environment of rivers and lakes, the construction of underground regulating reservoirs and underground sewage treatment plants is increasing day by day. Underground regulating reservoirs and underground sewage treatment plants are generally pure basement structures, built near rivers and lakes, and the groundwater level is usually high. In order to improve the anti-floating ability of underground buildings, pull-out piles and pull-out anchors are generally set up. For foundation pits full of pull-out piles, if the planer cannot break the excavated hard rock, blasting is required. In the subway field, the technology of deep foundation pit base blasting for the safety impact of deep foundation pits has become increasingly mature, but the technology of the quality impact of pull-out piles is still immature. With the rapid development of municipal water projects, underground regulating reservoirs and underground sewage treatment plant projects are increasing day by day. The main advantages of the construction method of pile group deep foundation pit blasting are as follows:

[0003] First, blast the rock in the groove area to form an open surface for the non-groove area, which is convenient for stress release during the blasting process. The groove area is divided into the upper groove area and the lower groove area. The upper groove area is blasted to the top of the pull-out pile over-filled with concrete, and micro-blasting holes are arranged in the vicinity of the pull-out pile in the lower groove area to reduce the shear deformation of the pull-out pile caused by the transverse wave during the blasting of the main blasting hole and avoid extrusion. After the rock in the groove area is cleared and transported out, the rock in the non-groove area forms an open surface, which is more convenient for blasting. The pile foundation is the foundation of the building. The integrity of the pull-out pile plays a decisive role in the anti-floating of pure underground buildings, and is directly related to the safety and life of the underground building. Through the construction method of blasting the hard rock at the bottom of the traditional deep foundation pit, the transverse wave generated by the blasting may cause shear damage such as cracking and broken piles to the pull-out piles (engineering piles). Summary of the invention

[0004] In order to overcome the technical problems in the prior art, the present invention provides a construction method for low-impact deep foundation pit hard rock blasting of pile groups, which adopts a combined blasting method of "pre-cracking + layered blasting in the grooving area, controlled blasting in the non-grooving area, and buffering + weak blasting control in the area adjacent to the piles", which not only improves the blasting efficiency, but also improves the finished product protection of the pull-out piles, thereby solving the above-mentioned technical problems.

[0005] A construction method for low-impact deep foundation pit hard rock blasting of pile groups, firstly grooves the rock at the bottom of the deep foundation pit to form an air-facing surface in the non-grooving area, then controlled blasting is adopted in the non-grooving area, and in order to protect the finished product quality of the pull-out piles, micro-blasting holes are arranged in the area adjacent to the piles in the lower grooved area, and the micro-blasting holes are blasted before the main blasting holes, and buffer holes and micro-blasting holes are arranged in the area adjacent to the piles in the lower non-grooving area, and explosives are not loaded in the buffer holes, and the micro-blasting holes are blasted later than the main blasting holes.

[0006] The construction method comprises the following steps:

[0007] S1: Micro-explosion holes and main blasting holes are arranged in the upper grooving area. A row of micro-explosion holes is arranged around the grooving area. The width of the grooving area is 10m. The spacing between micro-explosion holes is 1m, and the hole diameter is 90mm. The spacing between main blasting holes is 2m. They are arranged in a plum blossom shape with a hole diameter of 90mm. Micro-explosion holes are detonated before main blasting holes. After blasting, the rocks in the upper grooving area are cleaned.

[0008] S2: Main blast holes are arranged in the lower groove area, and micro blast holes are arranged in the area adjacent to the piles. The spacing between micro blast holes is 0.4m, and the hole diameter is 76mm. The spacing between main blast holes is 0.5m×0.6m, arranged in a plum blossom shape, and the hole diameter is 40mm. Micro blast holes are detonated before main blast holes. After blasting, the rocks in the lower groove area are cleaned;

[0009] S3: The main blasting holes are arranged in the upper non-grooving area adjacent to the formed free surface. The upper non-grooving area adopts single-hole single-shot millisecond delay loosening and de-agglomeration energy controlled blasting. The free surface has been formed. The spacing and charging amount of the main blasting holes in the non-grooving area can be larger than those in the grooving area. The spacing between the main blasting holes in this area is 2.5m×3m, the hole diameter is 90mm, the diameter of the de-agglomeration iron ball is 70mm, and the de-agglomeration iron ball is continuously charged. After the blasting is completed, the rocks in the upper non-grooving area are cleaned up. The blasting work in the non-grooving area is carried out sequentially from the grooving area to both sides.

[0010] S4: After the rocks in the upper non-grooving area are cleared and transported out, the main blast holes in the lower non-grooving area of ​​the corresponding area are arranged; in order to protect the pull-out piles, buffer holes and micro-blast holes are arranged in the area adjacent to the piles. The main blast holes in this area are 2.5m×3m apart, with a hole diameter of 90mm, and 0.9kg of 2# rock emulsion explosive is loaded in each hole. The micro-blast holes are 1m apart, with a hole diameter of 90mm, and the buffer holes are 1.5m apart, with a hole diameter of 90mm; the buffer holes are 1.5m away from the micro-blast holes. The main function of the buffer holes is to reduce the vibration caused by the blasting. The main blast holes in this area are detonated before the micro-blast holes.

[0011] In general, compared with the prior art, the above technical scheme conceived by the present invention can achieve the following beneficial effects: the present invention provides a construction method for low-impact deep foundation pit hard rock blasting of pile groups, which adopts a combined blasting method of "pre-cracking + layered blasting in the grooving area, controlled blasting in the non-grooving area, and buffering + weak blasting control in the area adjacent to the piles". Through the construction method of combined blasting, the impact on the pile foundation during the blasting process is effectively reduced, the safety factor of the finished product protection of the engineering piles is improved, and the quality and pass rate of the pile body are ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings, wherein:

[0013] Figure 1 A schematic diagram of hard rock blasting zoning for a low-impact deep foundation pit with a pile group according to the present invention;

[0014] Figure 2 It is a schematic diagram of the arrangement of the blasting holes in the upper layer of the groove drawing area in an embodiment of the present invention;

[0015] Figure 3 It is a schematic diagram of the arrangement of the lower layer blasting holes in the groove drawing area in an embodiment of the present invention;

[0016] Figure 4 This is a schematic diagram of the charge structure in the non-grooving area in an embodiment of the present invention;

[0017] Figure 5 It is a schematic diagram of the arrangement of blasting holes in the area adjacent to the pile in an embodiment of the present invention;

[0018] In the figure: 1-grooving area, 2-non-grooving area, 3-pile adjacent area, 4-micro blasting hole, 5-main blasting hole, 6-energy-dissipating iron ball. DETAILED DESCRIPTION

[0019] like Figure 1 As shown, it is a schematic diagram of hard rock blasting zoning of a pile group low-impact deep foundation pit of the present invention. First, grooves are made in the rock at the bottom of the deep foundation pit to form an air-facing surface in the non-grooving area 2, and then controlled blasting is adopted in the non-grooving area 2. To protect the quality of the finished product of the pull-out pile, micro-blasting holes 4 are arranged in the pile adjacent area 3 of the lower grooved area 1, and the micro-blasting holes 4 are blasted before the main blasting holes 5. Buffer holes and micro-blasting holes 4 are arranged in the pile adjacent area 3 of the lower non-grooving area 2, and no explosives are loaded in the buffer holes. The micro-blasting holes 4 are blasted later than the main blasting holes 5.

[0020] The construction method comprises the following steps:

[0021] Step 1: Arrange micro-explosion holes 4 and main explosion holes 5 on the upper layer of the groove area 1. The blasting holes are arranged as follows: Figure 2 As shown, a row of micro-explosion holes 4 are arranged around the groove area 1. The width of the groove area 1 is 10m. The spacing between micro-explosion holes 4 is 1m, the hole diameter is 90mm, and a single hole is loaded with 1.5kg of 2# rock emulsion explosives, and the air interval is charged; the main blasting holes 5 are 2m apart, arranged in a plum blossom shape, with a hole diameter of 90mm, and a single hole is loaded with 8.2kg of 2# rock emulsion explosives. The explosives are continuously charged, and an industrial electronic detonator detonation network is used. The detonation is delayed from the middle to both sides hole by hole. The micro-explosion hole 4 is detonated first by 100ms-150ms before the main blasting hole 5 in the near row. The delay time between the main blasting holes 5 is 17ms. After the blasting is completed, the rocks in the upper groove area 1 are cleaned;

[0022] Step 2: After the upper rock of the trough area 1 is cleaned and transported out, the main blast hole 5 is arranged in the lower layer of the trough area, and the micro blast hole 4 is arranged in the pile adjacent area 3. The blast hole arrangement is as follows: Figure 3As shown, the spacing between micro-explosion holes 4 is 0.4m, the hole diameter is 76mm, and each hole is loaded with 0.1kg of 2# rock emulsion explosive, and the air interval is charged; the spacing between main blasting holes 5 is 0.5m×0.6m, arranged in a plum blossom shape, with a hole diameter of 40mm, and each hole is loaded with 0.15kg of 2# rock emulsion explosive, and the charge is continuously charged. Micro-explosion hole 4 is detonated before main blasting hole 5, and the rock in the lower groove area 1 is cleaned after the blasting is completed;

[0023] Step 3: The main blasting holes 5 are arranged adjacent to the upper non-grooving area 2 where the free surface has been formed. The upper non-grooving area 5 adopts single-hole single-shot millisecond delay loosening and de-agglomeration controlled blasting. The free surface has been formed. The spacing and charge of the main blasting holes 5 in the non-grooving area 2 can be greater than those in the groove area 1. The spacing between the main blasting holes 5 in this area is 2.5m×3m, and the hole diameter is 90mm; Figure 4 As shown, it is a schematic diagram of the charging structure of the non-grooving area 2. A single hole is loaded with 3.6 kg of 2# rock emulsion explosive. A flexible cushion layer with a thickness of 230 mm is arranged at the bottom of the hole. The diameter of the deagglomerated iron ball 6 is 70 mm. The upper part of the deagglomerated iron ball 6 is continuously loaded with explosives. The rocks in the upper non-grooving area 2 are detonated and cleaned. The blasting work in the non-grooving area 2 is carried out sequentially from the grooving area 1 to both sides.

[0024] Step 4: After the rocks in the upper non-grooving area 2 are cleaned and transported out, the main blast holes 5 in the lower non-grooving area 2 of the corresponding area are arranged. To protect the pull-out piles, buffer holes and micro blast holes 4 are arranged in the pile adjacent area 3, such as Figure 5 As shown in the figure, it is a schematic diagram of the arrangement of blasting holes in the pile adjacent area 3. The main blasting holes 5 in this area have a hole spacing of 2.5m×3m, a hole diameter of 90mm, and a single hole is loaded with 0.9kg of 2# rock emulsion explosive; the micro-blasting holes 4 have a hole spacing of 1m, a hole diameter of 90mm, and a single hole is loaded with 0.3kg of 2# rock emulsion explosive, with air interval charging; the buffer holes have a hole spacing of 1.5m and a hole diameter of 90mm; the buffer hole is 1.5m away from the micro-blasting hole 4, and no explosives are installed in the buffer hole. Its main function is to reduce the vibration caused by blasting. The main blasting hole 5 in this area is detonated before the micro-blasting hole 4.

[0025] When conducting layered slot blasting, small-scale upper slot blasting and lower shallow hole slot blasting tests are carried out according to the blasting design parameters. During the blasting test, vibration monitoring points are set up on the top rock surface of the pull-out piles in the blasting area to monitor the blasting vibration, and the integrity of the pull-out piles is tested after blasting and excavation to verify the rationality of the design parameters. After verification, large-scale slot blasting is carried out. After the slot area 1 is formed, tests are also required before starting large-scale blasting operations in the deep hole micro-difference loosening control blasting area.

[0026] During the blasting process, the vibration velocity of the pull-out piles needs to be monitored. If the vibration velocity is less than the safe allowable particle vibration velocity, the quality of the pile foundation can be guaranteed.

Claims

1. A construction method for low-impact deep foundation pit hard rock blasting with pile groups, characterized in that: The invention comprises a groove area (1), a non-groove area (2), a pile adjacent area (3), micro-blasting holes (4), a main blasting hole (5), and a deagglomerated iron ball (6). The construction method comprises the following steps through a combined blasting method of "pre-cracking in the groove area + layered blasting, controlled blasting in the non-groove area, buffering in the pile adjacent area + weak blasting control": S1: In the upper groove area (1), micro-explosion holes (4) and main explosion holes (5) are arranged, and the surrounding micro-explosion holes (4) and the main explosion holes (5) are exploded together to clean the rocks in the upper groove area (1) after blasting; S2: In the lower groove area (1), the main blast hole (5) is laid out, and the micro blast hole (4) is laid out in the area adjacent to the pile → the micro blast hole (4) in the area adjacent to the pile (3) is detonated together with the main blast hole (5), and the rock in the lower groove area (1) is cleaned after blasting; S3: The upper non-grooving area (2) forms an open surface, and main blasting holes (5) are arranged in different areas. The main blasting holes (5) are blasted together → the rocks in the upper non-grooving area (2) are cleaned after blasting; S4: In the lower non-grooving area (2), main blast holes (5) are arranged in different areas, buffer holes and micro blast holes (4) are arranged in the pile adjacent area (3), and the main blast holes (5) and micro blast holes (4) are blasted together to clean the rocks in the lower non-grooving area (2). Mechanical coordination is used to break the local unbroken areas.

2. The construction method of low-impact deep foundation pit hard rock blasting by pile group according to claim 1 is characterized in that: The micro-blasting hole (4) and the main blasting hole (5) are both blasting holes with a diameter of 90 mm, and 2# rock emulsion explosives are installed inside. The diameter and roll length of the explosives installed in the micro-blasting hole (4) are smaller than those in the main blasting hole (5), and no explosives are installed in the buffer hole outside the pile adjacent area (3).

3. The construction method of low-impact deep foundation pit hard rock blasting by pile group according to claim 1 is characterized in that: The micro-explosion hole (4) is equipped with an emulsion explosive with a diameter of 32 mm and a single explosive roll length of 300 mm. The main explosion hole (5) is equipped with an emulsion explosive with a diameter of 70 mm and a single explosive roll length of 450 mm. The bottom of the main explosion hole (5) in the non-grooving area (2) is equipped with a soft cushion layer and a deagglomerated iron ball (6).

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