CN110820778A

CN110820778A - Local precipitation construction method for foundation pit

Info

Publication number: CN110820778A
Application number: CN201911022843.0A
Authority: CN
Inventors: 任文艺; 杨亚军; 井文奇
Original assignee: Shaanxi Shenzhou Industry Co Ltd
Current assignee: Shaanxi Shenzhou Industry Co Ltd
Priority date: 2019-10-25
Filing date: 2019-10-25
Publication date: 2020-02-21

Abstract

The invention relates to a construction method for local dewatering of a foundation pit, relates to the technical field of foundation dewatering, and aims to solve the problem that the conventional dewatering well is easy to collapse due to the impact of underground water and even the slurry on the well wall collapses to block a drainage pump. Which comprises the following steps: s1: determining the size, the number and the position of the dewatering wells; s2: manufacturing a downcomer; s3: excavating a water collecting pit; s4: fixing the downcomer; s5: filling a filter layer; s6: and (5) constructing a waterproof layer. The method has the beneficial effect of reducing the hole collapse phenomenon of the precipitation well.

Description

Local precipitation construction method for foundation pit

Technical Field

The invention relates to the technical field of foundation precipitation, in particular to a construction method for local precipitation of a foundation pit.

Background

The foundation pit dewatering refers to dewatering work performed for ensuring that the foundation pit can be constructed under a dry condition and preventing the problems of slope instability, basic quicksand, pit bottom uplift, pit bottom piping, foundation bearing capacity reduction and the like when the foundation pit is excavated deeply and underground water level is high during construction of a high-rise building and the foundation pit is excavated under the dry condition.

The foundation pit dewatering method mainly comprises the following steps: open ditch water collecting well precipitation, light well point precipitation, jet well point precipitation, electroosmosis well point precipitation, deep well point precipitation and the like. When the bottom of a foundation pit of a building main body is higher than the underground water level and a water collecting pit of a local place such as a fire elevator is higher than the underground water level, local precipitation treatment needs to be carried out on the foundation pit, and when local precipitation is carried out, a well point precipitation method is a common method, namely, before excavation of the foundation pit, a certain number of water filter pipes (wells) are buried around the foundation pit, and water is pumped by using water pumping equipment to enable the excavated soil to be kept in a dry state all the time.

The invention of CN110093941A provides a deep foundation pit dewatering construction method, which comprises the following steps: s1) determining the structure, the design well depth and the design position of each precipitation well in the deep foundation pit according to the construction requirements, calculating the number of precipitation wells required in the deep foundation pit, and generating a deep foundation pit precipitation well construction scheme; s2) determining the actual position of the dewatering well according to the construction scheme of the dewatering well; s3) carrying out drilling construction by using a drilling machine at the actual position of each dewatering well to be constructed to form the dewatering well; s4) installing a drainage pump at the bottom of the dewatering well, injecting clean water into the dewatering well and pumping water by using the drainage pump to perform well washing operation until the water is cleaned and sand is removed, and completing construction of the dewatering well; s5) after the underground water gushes into the precipitation well and reaches a predetermined height, pumping the underground water gushes out of the precipitation well by using a drainage pump to complete the precipitation operation.

The deep foundation pit dewatering construction method provided by the invention has the advantages that the construction amount is small, the construction safety is enhanced, the construction efficiency is improved, but a dewatering well is formed by directly drilling on the foundation, so that the hole collapse is easily caused by the impact of underground water in the later construction process, and even slurry on the well wall collapses to block a drainage pump.

Disclosure of Invention

The invention aims to provide a local dewatering construction method for a foundation pit, which has the beneficial effect of reducing the hole collapse phenomenon of a dewatering well.

The above object of the present invention is achieved by the following technical solutions:

a local precipitation construction method for a foundation pit comprises the following steps:

s1: determining the size, the number and the position of the precipitation wells, determining the well depth and the pore diameter of the precipitation wells according to the depth of the foundation pit and the height of the underground water level, and calculating the number and the excavation positions of the precipitation wells according to the area and the direction of the foundation pit;

s2: manufacturing a dewatering pipe, wherein the dewatering pipe is manufactured according to the set dewatering well depth and the set dewatering well aperture, the height of the dewatering pipe is higher than the preset height, the inner diameter of the dewatering pipe is equal to the preset dewatering well aperture, a drainage pump and a drainage pipe are arranged in the dewatering pipe, and a plurality of dewatering holes are formed in the side wall of one end of the dewatering pipe;

s3: excavating a water collecting pit, wherein the water collecting pit is positioned at a position needing to be lowered in the local part of the foundation pit, the depth of the water collecting pit is greater than that of a preset foundation pit, and the bottom of the water collecting pit is lower than the height of the underground water level;

s4: fixing a downcomer, and vertically placing the end of the downcomer, which is provided with a downcomer hole, in the sump;

s5: filling a filter layer, filling gravel filter materials around the downcomer to form the filter layer, and enabling the upper end of the filter layer to reach the elevation part at the bottom of the foundation pit;

s6: and (5) constructing a waterproof layer, wherein the waterproof layer is arranged above the filter layer.

Through adopting above-mentioned technical scheme, bury the downcomer in the sump pit, the effect of well cementation is played that the downcomer can be better, prevents that earth on the well bore outer wall from collapsing in the well bore, forms mud and blockking up the drain pump, and the setting of the filter bed all around of downcomer has not only played fixed effect to the downcomer, can also play the effect of filtering groundwater simultaneously, prevents that the silt that smugglies secretly in the groundwater from blockking up the drain pump or blockking up the water hole that falls in the downcomer flows into from the water hole. The flow process of underground water is as follows: the underground water passes through the filter layer and enters the precipitation pipe through the precipitation holes on the precipitation pipe, is gathered in the precipitation pipe, is pumped out by the precipitation pump when reaching the height of the precipitation pump, and continuously flows into the precipitation pipe when the liquid level in the precipitation pipe is lower than the underground water level, so that the effect of reducing the water level is achieved; the waterproof layer is used for isolating underground water and further preventing the underground water from overflowing. The dewatering structure built by the construction method can well prevent the dewatering well from collapsing holes, so that the drainage pump is protected, and the smooth water pumping process is guaranteed.

The invention is further configured to: and a water stop ring is axially arranged on the outer wall of the precipitation pipe in a surrounding manner and is perpendicular to the precipitation pipe, and the water stop ring is arranged at one end of the precipitation pipe, which is far away from the precipitation hole.

By adopting the technical scheme, the water stop ring can better prevent water at the position close to the downcomer outside from overflowing along the downcomer due to the fact that the water cannot flow into the downcomer through the downcomer hole.

The invention is further configured to: the water falling holes and the end parts provided with the water falling holes are wrapped with non-woven fabrics.

Through adopting above-mentioned technical scheme, the filter layer is worn in the further secret aquatic of keeping apart of non-woven fabrics and reachs the outside silt of downcomer, prevents that it from entering into in the downcomer and blockking up the drain pump.

The invention is further configured to: a mounting frame is arranged in the downcomer, the drainage pump is arranged on the mounting frame, and a drainage pipe is connected to the drainage pump; and a liquid level sensor is further fixed in the downcast pipe and connected with a controller, and the controller controls the draining pump to automatically pump water.

By adopting the technical scheme, when the liquid level sensor senses that the water level in the precipitation pipe rises to the set height, the signal is fed back to the controller, the controller controls the drainage pump to pump water, when the liquid level drops to the set height, the liquid level sensor feeds back the signal to the controller again, the controller immediately controls the drainage pump to stop pumping water, and finally the effect of automatically controlling the pumping water is achieved, so that the liquid level below the construction foundation is controlled in the safe height, and the phenomenon that the underground water level moves upwards to influence the construction is prevented.

The invention is further configured to: and one end of the precipitation pipe, which is far away from the precipitation hole, is provided with a smooth flanging.

Through adopting above-mentioned technical scheme, turn-ups set up and make the downcomer upper end be in comparatively slick and sly state, prevent that the downcomer from taking place the phenomenon that the drain pipe splits.

The invention is further configured to: in S4, a layer of gravel packing is first laid on the bottom of the sump before the downcomer is secured, which downcomer rests on the gravel packing.

Through adopting above-mentioned technical scheme, the gravel packs can be followed downcomer below and filtered the silt in the stratum, prevents that silt from blockking up the drain pump.

The invention is further configured to: the S6 specifically includes the following steps:

s61: laying a first waterproof cloth;

s62: pouring a concrete cushion layer;

s63: laying a second waterproof cloth;

s64: and (5) pouring a concrete protective layer.

Through adopting above-mentioned technical scheme, first tarpaulin and second tarpaulin play the effect of keeping apart groundwater, and concrete cushion and concrete protective layer all play the effect of support to first tarpaulin and second tarpaulin for groundwater pressure can be resisted better to first tarpaulin and second tarpaulin, keeps leveling, and avoids tearing.

The invention is further configured to: the S6 is followed by S7: the protection waterproof layer is before the concrete protective layer hardens completely, erects the reinforcing bar net protective cover above it, the reinforcing bar net protective cover is the crisscross support body that welds and form of reinforcing bar, and each reinforcing bar of constituteing the reinforcing bar net protective cover makes the reinforcing bar net protective cover unsettled frame locate the concrete protective layer top to one side bending in the tip.

Through adopting above-mentioned technical scheme, steel bar protecting cover supports in concrete protection layer top, has certain rigidity, prevents that personnel or equipment from passing through from the top carelessly and destroying the waterproof layer, plays certain guard action, can not shelter from the sunlight again simultaneously, has guaranteed the normal drying and the solidification shaping of waterproof layer.

In conclusion, the beneficial technical effects of the invention are as follows:

1. by embedding the dewatering pipe, the phenomenon of hole collapse of the dewatering well is well prevented, so that the drainage pump is protected, the water suction pump is prevented from being blocked, and the smooth water suction process is ensured;

2. by arranging the waterproof layer, the effects of isolating underground water and preventing the overflow of the underground water are achieved;

3. establish the steel bar protection cover through covering on the waterproof layer, when preventing that personnel or equipment from passing through from the top carelessly and destroying the waterproof layer, can not shelter from the sunlight again, guaranteed the normal drying and the solidification shaping of waterproof layer.

Drawings

FIG. 1 is a process diagram of a local precipitation construction method for a foundation pit according to the disclosure.

Fig. 2 is a process diagram of step S6.

Fig. 3 is a view of a structure of a foundation pit precipitation structure constructed according to the method for local precipitation construction of the foundation pit disclosed by the invention.

In the figure, 1, a sump; 2. a gravel pack; 3. a filtering layer; 4. a downcomer pipe; 41. flanging; 42. a water dropping hole; 43. a water stop ring; 5. draining pump; 6. a liquid level sensor; 7. a mounting frame; 8. a drain pipe; 9. a waterproof layer; 91. a first tarpaulin; 92. a concrete cushion; 93. a second tarpaulin; 94. a concrete protective layer; 10. reinforcing mesh protective cover.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

Referring to fig. 1, the invention discloses a local precipitation construction method for a foundation pit, which comprises the following steps:

s1: determining the size, the number and the position of the precipitation wells, determining the well depth and the pore diameter of the precipitation wells according to the depth of the foundation pit and the height of the underground water level, and calculating the number and the excavation position of the precipitation wells according to the area and the direction of the foundation pit.

S2: and manufacturing the dewatering pipe 4, and manufacturing the dewatering pipe 4 according to the well depth and the pore diameter of the dewatering well set in the first step.

Referring to fig. 3, the height of the downcomer 4 is higher than a preset height to prevent the overflow of the water surface, and the inner diameter of the downcomer 4 is equal to the preset aperture of the dewatering well; a plurality of water reducing holes 42 are densely formed in the side wall of one end of the water reducing pipe 4 within 1m, the diameter of each water reducing hole 42 is smaller than 1cm, and non-woven fabrics are integrally coated in the range of the water reducing holes 42 and the end part provided with the water reducing holes 42; perpendicular to 4 axial of downcomer encloses on 4 outer walls of downcomer and is equipped with seal ring 43, and seal ring 43 welds in the position of 4 ends of keeping away from the downcomer hole 42, and the width of seal ring 43 is 300mm, and seal ring 43 can be better prevent 4 outside of downcomer near 4 water of position of downcomer and because too late the water that flows into downcomer pipe 4 through the downcomer hole 42 and on 4 overflows along downcomer pipe.

In order to reduce the subsequent installation difficulty of the drainage pump 5, the end, close to the drainage hole 42, in the drainage pipe 4 is provided with the installation frame 7, the drainage pump 5 is detachably connected to the installation frame 7, the drainage pipe 8 is connected to the drainage pump 5, one end of the drainage pipe 8 leads to one end, close to the drainage hole 42, of the drainage pipe 5, and the other end extends out of the drainage pipe 4 from one end, far away from the drainage hole 42, of the drainage pipe 4; still be fixed with level sensor 6 in the downcomer 4, level sensor 6 connection director, controller control drain pump 5 is automatic to be drawn water, cuts off drain pipe 8 or damages for preventing the sharp-pointed tip of downcomer 4, and downcomer 4 is kept away from and is fallen water hole 42 one end and be provided with slick and sly turn-ups 41.

S3: excavating a water collecting pit 1, wherein the water collecting pit 1 is positioned at the position of the foundation pit where water needs to be lowered locally, the depth of the water collecting pit 1 is larger than the depth of the preset foundation pit by 1.3m, and the bottom of the water collecting pit 1 is lower than the height of the underground water level.

S4: the fixed downcomer 4, at first lay the gravel packing 2 that the one deck particle size is 30mm ~ 50mm at sump pit 1 bottom, gravel packing 2 lays the thickness and is 300mm, then will descend the one end that downcomer 4 was provided with the hole 42 that falls downwards, vertically lay in sump pit 1, gravel packing 2 can be followed the downcomer 4 below and filtered the silt in the stratum, prevents that silt from blockking up drain pump 5.

S5: filling a filter layer 3, filling gravel filter materials with the grain diameter of 30-50 mm around the downcomer 4 to form the filter layer 3 around the downcomer 4, and enabling the upper end of the filter layer 3 to reach the elevation of the bottom of the foundation pit.

S6: constructing a waterproof layer 9, arranging the waterproof layer 9 above the filter layer 3, and referring to fig. 2, the method comprises the following steps:

s61: laying a first tarpaulin 91;

s62: pouring a concrete cushion 92;

s63: laying a second tarpaulin 93;

s64: and pouring the concrete protective layer 94.

The first tarpaulin 91 and the second tarpaulin 93 are made of polypropylene fibre cloth.

First tarpaulin 91 and second tarpaulin 93 play the effect of keeping apart groundwater, and concrete cushion 92 and concrete protection layer 94 all play the effect of support to first tarpaulin 91 and second tarpaulin 93 for underground water pressure can be resisted better to first tarpaulin 91 and second tarpaulin 93, keeps leveling, and avoids tearing.

S7: the protective waterproof layer 9 is constructed by erecting a mesh reinforcement protective cover 10 on the concrete protective layer 94 before the concrete protective layer is completely hardened, wherein the mesh reinforcement protective cover 10 is a frame body formed by welding reinforcing bars in an interlaced manner, and the ends of the reinforcing bars constituting the mesh reinforcement protective cover 10 are bent to one side so that the mesh reinforcement protective cover 10 is suspended and erected on the concrete protective layer 94. The steel bar protecting cover is supported above the concrete protecting layer 94, has certain rigidity, prevents personnel or equipment from damaging the waterproof layer 9 through careless passing from the top, plays a certain protective role, can not shelter from sunlight at the same time, and ensures normal drying and solidification forming of the waterproof layer 9.

The foundation pit dewatering structure built by the dewatering construction method provided by the embodiment of the invention has the dewatering principle as follows: through setting up the effect of playing the well cementation that downcomer 4 can be better, prevent that earth on the well bore outer wall from collapsing in the well bore, form mud and stop up drain pump 5, downcomer 4 filter layer 3's all around setting up has not only played fixed effect to downcomer 4, can also play the effect of filtering groundwater simultaneously, prevents that the silt that smugglies secretly in the groundwater from blockking up drain pump 5 or stopping up the hole 42 that falls in downcomer 4 from the hole 42 that falls. The underground water passes through the filter layer 3 and enters the downcomer 4 through the dewatering holes 42 on the downcomer 4 to be gathered in the downcomer 4, the position sensor senses that the water level in the downcomer 4 rises to a set height, the signal is fed back to the controller, the controller controls the drainage pump 5 to pump water, when the liquid level drops to the set position, the liquid level sensor 6 feeds back the signal to the controller again, and the controller immediately controls the drainage pump 5 to stop pumping water;

when rain or precipitation holes 42 are blocked, groundwater does not enter from the precipitation holes 42, the water level may move upwards, and the water baffle and the waterproof layer 9 can be used for isolating groundwater to prevent groundwater from overflowing.

The embodiments of the present invention are preferred embodiments of the present invention, and the scope of the present invention is not limited by these embodiments, so: all equivalent changes made according to the structure, shape and principle of the invention are covered by the protection scope of the invention.

Claims

1. A local precipitation construction method for a foundation pit is characterized by comprising the following steps:

s2: manufacturing a dewatering pipe (4), manufacturing the dewatering pipe (4) according to the set dewatering well depth and the set dewatering well aperture, wherein the height of the dewatering pipe (4) is higher than the preset height, the inner diameter of the dewatering pipe (4) is equal to the preset dewatering well aperture, and a plurality of dewatering holes (42) are formed in the side wall of one end of the dewatering pipe (4);

s3: excavating a water collecting pit (1), wherein the water collecting pit (1) is positioned at a position needing to lower water at the local part of the foundation pit, the depth of the water collecting pit (1) is greater than that of a preset foundation pit, and the bottom of the water collecting pit (1) is lower than the height of the underground water level;

s4: the water descending pipe (4) is fixed, and one end of the water descending pipe (4) provided with the water descending hole (42) faces downwards and is vertically placed in the water collecting pit (1);

s5: filling a filter layer (3), filling gravel filter materials around the downcomer (4) to form the filter layer (3), and enabling the upper end of the filter layer (3) to reach the elevation part of the bottom of the foundation pit;

s6: and constructing a waterproof layer (9), and arranging the waterproof layer (9) above the filter layer (3).

2. The method for local dewatering construction of a foundation pit according to claim 1, characterized in that: perpendicular to downcomer (4) axial encloses on downcomer (4) outer wall and is equipped with stagnant water ring (43), stagnant water ring (43) are located downcomer (4) are kept away from the one end of water hole (42) falls.

3. The method for local dewatering construction of a foundation pit according to claim 1, characterized in that: the water falling holes (42) and the end parts provided with the water falling holes (42) are coated with non-woven fabrics.

4. The method for local dewatering construction of a foundation pit according to claim 1, characterized in that: a mounting rack (7) is arranged in the downcomer (4), a drainage pump (5) is mounted on the mounting rack (7), and a drainage pipe (8) is connected to the drainage pump (5); still be fixed with level sensor (6) in downcomer (4), level sensor (6) connection director, the controller control drain pump (5) are automatic to draw water.

5. The method of local dewatering construction for a foundation pit according to claim 4, wherein: one end of the downcomer (4) far away from the water descending hole (42) is provided with a smooth flanging (41).

6. The method for local dewatering construction of a foundation pit according to claim 1, characterized in that: in the S4, before fixing the downcomer (4), a layer of gravel packing (2) is firstly paved at the bottom of the sump (1), and the downcomer (4) is placed on the gravel packing (2).

7. The method for local dewatering construction of a foundation pit according to claim 1, characterized in that: the S6 specifically includes the following steps:

s61: laying a first waterproof cloth (91);

s62: casting a concrete cushion (92);

s63: laying a second waterproof cloth (93);

s64: and pouring a concrete protection layer (94).

8. The method of local dewatering construction for a foundation pit according to claim 7, wherein: the S6 is followed by S7: protection waterproof layer (9), before concrete protective layer (94) hardens completely, erect reinforcing bar net protective cover (10) above it, reinforcing bar net protective cover (10) are the crisscross support body that welds of reinforcing bar, and each reinforcing bar of constituteing reinforcing bar net protective cover (10) is bent to one side at the tip and makes reinforcing bar net protective cover (10) unsettled frame locate concrete protective layer (94) top.