CN105421498B - A kind of foundation ditch water-impervious and subsidence control method based on three-dimensional curtain gang of wells system - Google Patents

Abstract

This method proposes a foundation pit anti-seepage and settlement control method based on the three-dimensional curtain-well group system, which consists of vertical curtains with different depths, horizontal curtain grids and dewatering wells in the foundation pit. On the basis of the traditional vertical unequal-depth curtain, a horizontal curtain grid structure is constructed to form a limited water-blocking body in the underground space. By rationally optimizing the well group structure and making full use of the curtain energy consumption principle, the water head loss during groundwater movement is increased. The purpose of reducing the groundwater level drawdown outside the foundation pit and thereby reducing the settlement amount is achieved. The three-dimensional curtain-well group system makes full use of the wall-well mechanism, which can effectively prevent the instability of the foundation pit caused by seepage and control the ground settlement caused by the dewatering of the foundation pit. The project quantity and project cost have good social and economic benefits.

Description

A foundation pit anti-seepage and settlement control method based on three-dimensional curtain-well group system

technical field

The invention belongs to the fields of geotechnical engineering and geological engineering, and in particular relates to a foundation pit anti-seepage water and settlement control method based on a three-dimensional curtain-well group system.

Background technique

During the dewatering process of the foundation pit, when the vertical water-stop curtain cannot completely cut off the precipitation aquifer, the extraction of groundwater from the foundation pit will have a large-scale impact on the precipitation target aquifer, which will lead to the waste of groundwater resources, the disturbance of the original hydrogeological environment, and the nearby Land subsidence and other issues, while drainage may also have a large burden on municipal facilities.

For foundation pits built in densely built areas, settlement needs to be controlled, and the methods that may be used are nothing more than isolation, lowering, and irrigation. However, recharge is often difficult to implement on a large scale due to unresolved site problems during the implementation process. Recharge is the reverse process of precipitation, and the combination of pumping and irrigation is a huge energy-consuming process. When the recharge well is close to the foundation pit, the drawdown in the foundation pit may not meet the standard. At the same time, recharge will lead to multi-period soil disturbance, which may intensify settlement and uneven deformation. At present, fully enclosed curtains (vertical curtains + horizontal curtains) have been used in domestic foundation pits to control groundwater, but the project cost is high. When the required horizontal curtain depth is large, the construction is difficult and the quality is difficult to control.

Contents of the invention

The purpose of the present invention is to provide a foundation pit anti-seepage water and settlement control method based on the three-dimensional curtain-well group system in order to overcome the above-mentioned technical defects.

The purpose of the present invention can be achieved through the following technical solutions:

A foundation pit anti-seepage and settlement control method based on a three-dimensional curtain-well group system is characterized in that the method utilizes vertical unequal depth curtains and horizontal curtain grid technology to form a three-dimensional curtain.

The vertical unequal-depth curtain 1 is arranged on the outer edge of the foundation pit (the vertical unequal-depth curtain belongs to the prior art) to prevent groundwater from flowing outward from the foundation pit under the action of the water level difference inside and outside the foundation pit. Horizontal seepage in foundation pits.

The horizontal curtain grid 2 refers to that when the simple vertical unequal depth curtain cannot meet the requirements of the external depth of the foundation pit or when there may be adverse phenomena such as quicksand, piping, and sudden surge at the bottom of the foundation pit, use rotary spray or high-pressure Grouting and other methods, a continuous cement-soil horizontal curtain grid with a certain strength and impermeability is set at a certain distance from the bottom of the pit. The key to the horizontal curtain grid 2 is to balance the buoyancy force of the groundwater to prevent the bottom of the pit from the self-weight of the horizontal seepage barrier, the friction between the engineering pile and the bottom plate, and the self-weight of a certain thickness of soil between the bottom plate and the bottom of the pit. surge. At the same time, part of the water blocking effect is used to increase the head loss during the vertical seepage of groundwater, so as to reduce the water level drawdown of the aquifer outside the foundation pit.

The well group system 3 is a widely used measure for artificially lowering the groundwater level (the well group system belongs to the prior art), and the well point dewatering refers to the burying of permeable dewatering wells in the foundation pit of the proposed project Points (arranged in a tubular shape), equipped with certain pumping equipment, pump out the groundwater continuously to reduce the groundwater level within the foundation pit to the required depth, so as to ensure that the foundation pit project can be carried out in a drier construction environment, and at the same time Meet the anti-surge requirements of foundation pits. In the present invention, the well group system 3 is laid out and the pumping wells are arranged above the horizontal curtain grid 2 according to the fixed well spacing.

This method combines two kinds of curtain forms and well group system 3, and builds a horizontal curtain grid structure on the basis of traditional vertical unequal-depth curtains to form a limited water-blocking body in the underground space. The energy consumption principle of the curtain increases the head loss during the groundwater movement, and achieves the purpose of reducing the groundwater level drawdown outside the foundation pit and thus reducing the settlement. The three-dimensional curtain-well group system makes full use of the wall-well mechanism, which can effectively control the ground subsidence caused by the dewatering of the foundation pit. At the same time, compared with the horizontal fully closed curtain, it greatly reduces the engineering quantity and construction cost, and has good social and economic benefits. benefit.

The main function of the vertical curtain in the three-dimensional curtain is to prevent seepage and surround the seepage, while the function of the horizontal curtain is to prevent seepage and dissipate energy. The groundwater pressure mainly depends on the soil weight on the upper part of the horizontal curtain to balance the water pressure under the curtain, realize energy dissipation at the outlet with limited thickness and seepage, reduce the outlet water pressure and reduce the pumping volume.

Description of drawings

Fig. 1 is the three-dimensional structure schematic diagram of the inventive method;

Fig. 2 is a top view structural diagram of the curtain grid horizontally;

Fig. 3 is the sectional view of the actual effect of the three-dimensional curtain-well group system;

Figure 4 is a technical flow chart of the three-dimensional curtain-well group system;

Marking instructions: 1-Vertical unequal depth curtain, 2-Horizontal curtain grid, 3-Dewatering well group, 4-Foundation pit bottom.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Principle analysis

The method of the invention proposes to form a three-dimensional curtain by utilizing vertical unequal-depth curtain and horizontal curtain grid technology.

The vertical unequal depth curtain is arranged on the outer edge of the foundation pit to prevent groundwater outside the foundation pit from seeping into the foundation pit under the action of the water level difference inside and outside the foundation pit, and to prevent seepage damage caused by quicksand and the like.

In addition to the role of seepage isolation, the three-dimensional curtain mainly cooperates with the pumping well group in the pit through seepage circumvention and energy dissipation, and constructs a local artificial roof in the aquifer, consumes energy through seepage resistance, and reduces the pumping volume of the well group. In the limited three-dimensional curtain Under the combined effect, the pumping wells are mainly used to achieve precipitation and decompression.

In this way, the conceptual model of the three-dimensional curtain-well group foundation pit precipitation system is constructed, and the three-dimensional curtain-well group system framework is established.

The horizontal curtain grid mentioned in the three-dimensional curtain proposed by this method means that when the simple vertical unequal depth curtain cannot meet the requirements of settlement control or there may be adverse phenomena such as quicksand, piping, and sudden surge at the bottom of the foundation pit, use a rotary A continuous cement-soil horizontal grid plate with a certain strength and impermeability is set at a certain distance from the bottom of the pit by spraying or high-pressure grouting. The key to the horizontal curtain grid is to balance the buoyancy force of the groundwater by the weight of the horizontal seepage barrier, the friction between the engineering pile and the bottom plate, and the soil weight of a certain thickness between the bottom plate and the bottom of the pit to prevent the bottom of the pit from bursting. Chung. That is, the vertical curtain should not be joined together with greater thickness and strength, and the groundwater pressure should not be balanced with increased weight. The water pressure under the curtain should be balanced mainly by the soil weight on the upper part of the horizontal curtain grid, and the energy dissipation at the outlet should be realized with limited thickness and seepage. Reduce outlet water pressure and reduce water pumping.

Aiming at the problems that the suspended vertical curtain in the foundation pit dewatering cannot effectively use the function of the wall well in the super deep foundation pit and the high cost of the closed curtain, a three-dimensional curtain system with vertical curtain and horizontal curtain separated is proposed. Different from the hanging curtain, the three-dimensional curtain constructs the horizontal curtain grid and works together with the vertical unequal depth curtain, and can realize water isolation, seepage reduction and energy dissipation in both horizontal and vertical directions. The difference from the closed curtain is that the horizontal curtain in the three-dimensional curtain is not connected with the vertical curtain, and the layout of the hall is not complete, and the water is not absolutely sealed. The seepage energy dissipation is used to reduce the outlet head pressure, reduce the precipitation pressure of the well group, and finally use the well group to achieve Precipitation decompression.

Example

In the specific embodiment, as shown in Fig. 1, the vertical unequal-depth curtain 1 construction is carried out at first, can adopt underground continuous wall usually for deep foundation pit, and vertical curtain bottom end is unequal depth, makes and impermeable support The protective piles are connected to form a vertical unequal depth curtain 1 . The horizontal curtain grid 2 can adopt methods such as high-pressure rotary spraying, MJS, grouting, etc., so that it will not be joined with the vertical curtain 1 of unequal depth with a large thickness and strength, and the horizontal curtain grid 2 is located on the bottom of the foundation pit 4 or less, and less than 1m from the bottom of the foundation pit, it plays a part of water blocking in the vertical direction of the foundation pit. The well group system 3 arranges the pumping wells in the foundation pit with a fixed well spacing in a uniform layout. Due to the addition of horizontal curtains, the number of them will be much smaller than that without horizontal curtains. The dewatering wells should be located above the horizontal curtain grid 2 , the groundwater is pumped out by the well group system 3 through the gap of the horizontal curtain grid 2 . Well group system 3 is composed of several precipitation wells.

The full name of MJS is: omni-directional high-pressure injection method.

As shown in Figure 3, under the action of the water level difference between the inside and outside of the foundation pit, the groundwater seeps horizontally from the outside of the foundation pit to the inside of the foundation pit, bypasses the vertical unequal depth curtain 1 and then flows to the horizontal curtain grid 2, the vertical unequal The deep curtain 1 plays a role of water blocking to a certain extent, but not completely water-proof. The groundwater continues to seep upward due to the buoyancy force. At this time, the horizontal curtain grid 2 uses the self-weight of the horizontal seepage barrier, the friction between the engineering pile and the bottom plate, and the self-weight of a certain thickness of soil between the bottom plate and the bottom of the pit to balance the groundwater. The buoyancy force is used to prevent sudden surges at the bottom of the pit. Part of the groundwater passes through the horizontal curtain grid 2 and is drawn out of the foundation pit by the well group system 3, which in turn realizes dewatering and decompression.

As shown in Figure 4, in the foundation pit engineering, in order to prevent the horizontal seepage of groundwater from the outside of the foundation pit to the inside of the foundation pit under the action of the water level difference between the inside and outside of the foundation pit, or the possibility of quicksand, piping, and inrush at the bottom of the foundation pit and other adverse phenomena, take precipitation and curtain partition measures, the precipitation is the well group system precipitation method, reduce the water head after reducing the pressure, reduce the pressure on the curtain; the curtain partition is the above-mentioned horizontal curtain grille 2 and The three-dimensional curtain combined with the vertical unequal-depth curtain 1 realizes energy dissipation at the outlet with limited thickness and seepage, reduces outlet water pressure and reduces water pumping. The three-dimensional curtain and the well group cooperate to form a three-dimensional curtain-well group system, which realizes precipitation control, and there is no obvious water level drop and settlement around the foundation pit.

Claims (1)

1. A foundation pit anti-seepage water and settlement control method based on a three-dimensional curtain-well group system, characterized in that it is composed of a vertical unequal depth curtain, a horizontal curtain grid and a dewatering well group in the foundation pit, and a three-dimensional Curtain-well cluster architecture, where: A three-dimensional curtain is formed by using a vertical unequal-depth curtain (1) and a horizontal curtain grid (2); On the basis of the traditional vertical unequal depth curtain (1), the horizontal curtain grid (2) structure is constructed to form a limited water blocking body in the underground space, Through the structure of the dewatering well group (3), the principle of curtain energy consumption is fully utilized to increase the water head loss during the groundwater movement, so as to reduce the groundwater level outside the foundation pit and thereby reduce the settlement; The three-dimensional curtain-well group system makes full use of the wall-well mechanism, which can effectively prevent the instability of the foundation pit caused by seepage and control the ground settlement caused by the dewatering of the foundation pit.