Self-starting negative pressure drainage system for draining groundwater in slope and construction method thereof

Abstract

A self-starting negative pressure drainage system for draining groundwater in a slope, includes: a declined borehole, a pipe boot, a permeable pipe and a drain pipe; wherein the declined borehole is divided into a permeable drilling section and a sealed grouting drilling section; wherein the permeable drilling section is on a lower portion of the declined borehole, and the sealed grouting drilling section is on an upper portion of the declined borehole; a water stop ring made of water-expanding rubber is provided between the permeable drilling section and the sealed grouting drilling section; the permeable drilling section comprises the permeable pipe; a top of the permeable pipe contacts the water-expanding rubber; a cavity is formed in the permeable pipe, an inlet of the drain pipe passes through the water stop ring made of water-expanding rubber and is inserted into the permeable pipe.

Claims

1. A self-starting negative pressure drainage system for draining groundwater in the slope, comprising: a declined borehole, a pipe boot, a permeable pipe and a drain pipe; wherein the declined borehole is divided into a permeable drilling section and a sealed grouting drilling section; wherein the permeable drilling section is on a lower portion of the declined borehole, and the sealed grouting drilling section is on an upper portion of the declined borehole; a water stop ring made of water-expanding rubber is provided between the permeable drilling section and the sealed grouting drilling section; the permeable drilling section comprises the permeable pipe and the pipe boot provided on a bottom of the permeable pipe; a top of the permeable pipe contacts the water-expanding rubber; a cavity is formed in the permeable pipe, groundwater is capable of penetrating into the cavity via the permeable pipe; an inlet of the drain pipe passes through the water stop ring made of water-expanding rubber and is inserted into the permeable pipe, an outlet of the drain pipe is provided on a low portion of the slope, and a height of the outlet is lower than a bottom hole height of the borehole; a gap between the drain pipe and the drilling wall of the sealed grouting drilling section is filled with the cement mortar; drainage capacity of the drain pipe, a maximum flow rate is greater than a flow rate of the groundwater of the slope permeated into the permeable drilling section.

2. The self-starting negative pressure drainage system for draining groundwater in the slope, as recited in claim 1, wherein a diameter of the borehole is greater than 90 mm.

3. The self-starting negative pressure drainage system for draining groundwater in the slope, as recited in claim 1, wherein the permeable pipe comprises outer woven filter cloth and perforated corrugated pipes made of HDPE (high-density polyethylene) as an inner support; the pipe boot adopts an HDPE pipe with a sealed bottom and an open top; wherein the drain pipe adopts a PA (polyamide) pipe with a diameter at a range of 4-8 mm.

4. A self-starting negative pressure drainage method for draining groundwater in the slope using the system as recited in claim 1, comprising steps of: (1) investigating geological conditions of a slope engineering; analyzing a buried depth of groundwater and a groundwater level to be controlled, and punching a borehole for drainage which is declined to enter a position below the safe groundwater level of the slope; (2) taking a length of a permeable pipe as a length of a permeable drilling section; inserting a bottom of the permeable pipe into a pipe boot for fixing; setting a water stop ring made of water-expanding rubber on a top of the permeable pipe; wherein an inlet of the drain pipe passes through the stop ring made of water-expanding rubber and is inserted in the permeable pipe; (3) inserting the pipe boot, the permeable pipe, the water stop ring made of water-expanding rubber and the drain pipe together into the permeable drilling section; setting an outlet of the drain pipe below the slope; and wherein a height of the outlet is less than a height of a bottom of the borehole; (4) after the water stop ring made of water-expanding rubber is fully expanded, filling cement mortar in a gap between the drain pipe and borehole wall of the sealed grouting drilling section; (5) when a height of water head of the inlet of the drain pipe is greater than a height of an aperture of the borehole which is caused by elevation of the groundwater of the slope, discharging groundwater in the permeable drilling section by the drain pipe under an effect of a head difference, in such a manner that drainage process occurs; wherein since the drainage capacity of the drain pipe is greater than a infiltration flow rate of the groundwater of the permeable drilling section, a siphon effect during a drainage process causes a negative pressure in the cavity to accelerate a flow of groundwater in the slope into the cavity; when the groundwater in the slope body and the cavity is drained off, air enters the inlet of the drain pipe, suction and discharge action of the drain pipe disappears, and a first drainage process is terminated; a drainage process circulates with the circulation of the rainfall infiltration.

5. A self-starting negative pressure drainage method for draining groundwater in the slope using the system as recited in claim 2, comprising steps of: (1) investigating geological conditions of a slope engineering; analyzing a buried depth of groundwater and a groundwater level to be controlled, and punching a borehole for drainage which is declined to enter a position below the safe groundwater level of the slope; (2) taking a length of a permeable pipe as a length of a permeable drilling section; inserting a bottom of the permeable pipe into a pipe boot for fixing; setting a water stop ring made of water-expanding rubber on a top of the permeable pipe; wherein an inlet of the drain pipe passes through the stop ring made of water-expanding rubber and is inserted in the permeable pipe; (3) inserting the pipe boot, the permeable pipe, the water stop ring made of water-expanding rubber and the drain pipe together into the permeable drilling section; setting an outlet of the drain pipe on a low portion out of the slope; and wherein a height of the outlet is less than a height of a bottom of the borehole; (4) after the water stop ring made of water-expanding rubber is fully expanded, filling cement mortar in a gap between the drain pipe and borehole wall of the sealed grouting drilling section; (5) when a height of water head of the inlet of the drain pipe is greater than a altitude of the borehole orifice which is caused by the rising of groundwater in a slope, discharging groundwater in the permeable drilling section by the drain pipe under an effect of a head difference, in such a manner that drainage process occurs; wherein since the drainage capacity of the drain pipe is greater than a infiltration flow rate of the groundwater of the permeable drilling section, a siphon effect during a drainage process causes a negative pressure in the cavity to accelerate a flow of groundwater in the slope into the cavity; when the groundwater in the slope body and the cavity is drained off, air enters the inlet of the drain pipe, suction and discharge action of the drain pipe disappears, and a first drainage process is terminated; a drainage process circulates with the circulation of the rainfall infiltration.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The FIGURE is a structural schematic view of a negative pressure self-starting drainage system and method for draining groundwater in a slope according to a preferred embodiment of the present invention.

(2) References in the Figure: 1borehole; 2cement mortar; 3water stop ring made of water-expanding rubber; 4permeable pipe; 5pipe boot; 6permeable drilling section; 7sealed grouting drilling section; 8drain pipe; 9outlet; 10slope; 11groundwater level.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(3) Further description of the present invention will be illustrated in detail combining with the preferred embodiments.

(4) The invention is further illustrated below in conjunction with specific embodiments. It is to be understood that the examples are merely illustrative of the invention and are not intended to limit the scope of the invention. In addition, it is to be understood that various modifications and changes may be made to the present invention, and the equivalents of the scope of the invention.

(5) Embodiment 1

(6) As shown in FIG. 1, the preferred embodiment provides a negative pressure self-starting drainage system and method for draining groundwater in a slope, comprising: a declined borehole 1, a pipe boot 5, a permeable pipe 4 and a drain pipe 8; wherein the declined borehole 1 is divided into a permeable drilling section 6 and a sealed grouting drilling section 7; wherein the permeable drilling section 6 is on a lower portion of the declined borehole 1, the sealed grouting drilling section 7 is on an upper portion of the declined borehole 1; a water stop ring made of water-expanding rubber 3 is provided between the permeable drilling section 6 and the sealed grouting drilling section 7; the permeable drilling section 6 comprises the permeable pipe 4 and the pipe boot 5; a top of the permeable pipe 4 contacts the water-expanding rubber 3; a cavity is formed in the permeable pipe 4, large particles of coarse sand and macadam are prevented from entering the cavity, and groundwater is capable of penetrating into the cavity via the permeable pipe 4; an inlet of the drain pipe 8 passes through the water stop ring 3 made of water-expanding rubber and is inserted into the permeable pipe 4, an outlet 9 of the drain pipe 8 is provided on a low portion of the slope, and a height of the outlet 9 is lower than a bottom hole height of the borehole 1; a gap between the drain pipe 8 and the drilling wall of the sealed grouting drilling section 7 is filled with the cement mortar 2, so as to block water-gas communication between an earth surface and the cavity of the permeable drilling section 6; the water stop ring 3 made of water-expanding rubber is configured to ensure that the cement mortar 2 of the sealed grouting drilling section 7 is prevented from entering the cavity of the permeable drilling section 6 during a grouting process; drainage capacity of the drain pipe 8. i.e., a maximum flow rate q.sub.2, should be greater than a flow rate q.sub.1 of the groundwater of the slope 10, in such a manner that a negative pressure is formed in the cavity, so as to pump groundwater around the borehole to achieve efficient drainage; wherein q.sub.1 can be estimated according to formula (1), and q.sub.2 can be estimated according to formula (2).

(7) $\begin{array}{cc}{q}_1=1.366\frac{K_0\left(H_0^2-h_{}^2\right)}{\lg \left(R/r_{}\right)};& \left(1\right)\end{array}$

(8) wherein K.sub.0 is a permeability coefficient of rock-soil body, H.sub.0 is a length of the permeable drilling section, h.sub. is a length of the drilling section below water surface in the borehole after drainage, R is a radius of influence, r.sub. is a radius of drainage borehole.

(9) $\begin{array}{cc}{q}_2=0.25d^{2}v\sqrt{\frac{2gh}{1++L/d}};& \left(2\right)\end{array}$

(10) wherein h is a head difference between the inlet and the outlet, is a coefficient of local resistance of the drain pipe; is a frictional resistant coefficient of the drain pipe, L and d are respectively pipe length and internal diameter of the drain pipe.

(11) A length of the sealed grouting drilling section 7 should satisfy a result that the water stop ring 3 made of water-expanding rubber is below the groundwater level 11 of the slope. Meanwhile, the length of the sealed grouting drilling section 7 is determined according to permeability coefficient of the rock-soil body. When the permeability coefficient of the rock-soil body is greater than 1 m/d, the length of the sealed grouting drilling section 7 is greater than 10 m; when the permeability coefficient of the rock-soil body is at a range of 1 m/d10.sup.1 m/d, the length of the sealed grouting drilling section 7 is at a range of 6-10 m; when the permeability coefficient of the rock-soil body is at a range of 10.sup.1 m/d10.sup.2 m/d, the length of the sealed grouting drilling section 7 is at a range of 3-6 m; when the permeability coefficient of the rock-soil body is less than 10.sup.2 m/d, the length of the sealed grouting drilling section 7 is greater than 3 m.

(12) In addition, a diameter of the borehole 1 should be greater than 90 mm. The permeable pipe 4 can adopt outer woven filter cloth and perforated corrugated pipes made of HDPE as inner support. The pipe boot 5 can adopt HDPE pipe with a sealed bottom and an open top. The drain pipe 8 can adopt a PA pipe with a diameter at a range of 4-8 mm. The drain pipe 8 has good gas-tightness, and is utilized for naturally starting draining when height of water head in the cavity is greater than a height of an aperture of the borehole which is caused by elevation of groundwater of the slope, so as to discharge groundwater in the slope in real time to control the groundwater below a safe water level.

(13) The present invention further provides a method utilizing the negative pressure self-starting drainage system for draining groundwater in a slope,

(14) comprising steps of:

(15) (1) investigating geological conditions of a slope engineering; analyzing a buried depth of groundwater and a groundwater level 11 to be controlled, and punching a borehole 1 for drainage which is declined to enter a position below the safe groundwater level 11 of the slope; wherein the borehole 1 can be provided on different positions on a surface of the slope, and the positions are determined according to factors comprising types of a rock-soil body, a slope gradient, rainfall characteristics of a slope area and a construction method;

(16) (2) taking a length of a permeable pipe 4 as a length of a permeable drilling section 6; inserting a bottom of the permeable pipe 4 into a pipe boot 5 for fixing; setting a water stop ring 3 made of water-expanding rubber on a top of the permeable pipe 4; wherein an inlet of the drain pipe 8 passes through the stop ring 3 made of water-expanding rubber and is inserted in the permeable pipe 4;

(17) (3) inserting the pipe boot 5, the permeable pipe 4, the water stop ring 3 made of water-expanding rubber and the drain pipe 8 together into the permeable drilling section 6; setting an outlet 9 of the drain pipe 8 below the slope; and wherein a height of the outlet 9 is less than a height of a bottom of the borehole 1;

(18) (4) after the water stop ring 3 made of water-expanding rubber is fully expanded, filling cement mortar 2 in a gap between the drain pipe 8 and borehole wall of the sealed grouting drilling section 7;

(19) (5) when a height of water head of the inlet of the drain pipe is greater than a height of an aperture of the borehole 1 which is caused by elevation of the groundwater of the slope, discharging groundwater in the permeable drilling section 6 by the drain pipe 8 under an effect of a head difference, in such a manner that drainage process occurs; wherein since the drainage capacity of the drain pipe 8 is greater than a infiltration flow rate of the groundwater of the permeable drilling section 6, a siphon effect during a drainage process causes a negative pressure in the cavity to accelerate a flow of groundwater in the slope into the cavity; when the groundwater in the slope body and the cavity is drained off, air enters the inlet of the drain pipe 8, suction and discharge action of the drain pipe 8 disappears, and a first drainage process is terminated; a drainage process circulates with the circulation of the rainfall infiltration.

(20) One skilled in the art will understand that the embodiment of the present invention as shown in the drawings and described above is exemplary only and not intended to be limiting.

(21) It will thus be seen that the objects of the present invention have been fully and effectively accomplished. Its embodiments have been shown and described for the purposes of illustrating the functional and structural principles of the present invention and is subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.