CN112064624B - Pile foundation for preventing and treating earthquake liquefaction landslide of engineering soil slope and construction method thereof - Google Patents

Pile foundation for preventing and treating earthquake liquefaction landslide of engineering soil slope and construction method thereof Download PDF

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CN112064624B
CN112064624B CN202010885376.0A CN202010885376A CN112064624B CN 112064624 B CN112064624 B CN 112064624B CN 202010885376 A CN202010885376 A CN 202010885376A CN 112064624 B CN112064624 B CN 112064624B
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grouting
pile foundation
soil
pipe
liquefaction
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CN112064624A (en
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章丽莎
魏骁
赵春艳
魏纲
张金红
崔允亮
王新泉
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Zhejiang University City College ZUCC
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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
    • E02D5/22—Piles
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D1/00—Investigation of foundation soil in situ
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D17/00—Excavations; Bordering of excavations; Making embankments
    • E02D17/20—Securing of slopes or inclines
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D17/00—Excavations; Bordering of excavations; Making embankments
    • E02D17/20—Securing of slopes or inclines
    • E02D17/207—Securing of slopes or inclines with means incorporating sheet piles or piles
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
    • E02D3/02—Improving by compacting
    • E02D3/10—Improving by compacting by watering, draining, de-aerating or blasting, e.g. by installing sand or wick drains
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B21/00—Alarms responsive to a single specified undesired or abnormal condition and not otherwise provided for
    • G08B21/02—Alarms for ensuring the safety of persons
    • G08B21/10—Alarms for ensuring the safety of persons responsive to calamitous events, e.g. tornados or earthquakes

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  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Structural Engineering (AREA)
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  • General Life Sciences & Earth Sciences (AREA)
  • Civil Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Paleontology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Soil Sciences (AREA)
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  • Chemical & Material Sciences (AREA)
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  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)

Abstract

The invention discloses a pile foundation for preventing and treating earthquake liquefaction landslide of an engineering soil slope and a construction method thereof, wherein the pile foundation comprises a pile foundation main body and an automatic earthquake liquefaction prevention and treatment system; the pile foundation main body comprises a pile cap, a hollow concrete pile foundation, a drain pipe, a grouting guide pipe and a grouting pipe; the automatic earthquake liquefaction prevention system comprises a pore pressure sensor, an acquisition instrument, an alarm and a water pump; when the pore water pressure around the pile foundation collected by the collector obviously rises and exceeds the early warning value, the alarm gives an alarm and starts the water pump to pump water, so that the pore water pressure of the soil body around the pile foundation is reduced in time, and the damage risk of the earthquake liquefaction landslide of the engineering soil side slope is prevented; when the conventional displacement monitoring method is adopted to monitor that the side slope is too large in deformation or too fast in deformation speed and exceeds an early warning value, the alarm gives an alarm, and the grouting limiter is used for positioning and grouting, so that the depth control of the earthquake liquefaction landslide damage of the engineering soil side slope is realized.

Description

Pile foundation for preventing and treating earthquake liquefaction landslide of engineering soil slope and construction method thereof
Technical Field
The invention relates to the technical field of earthquake liquefaction treatment of onshore geotechnical engineering, in particular to a pile foundation for preventing and treating earthquake liquefaction landslide of an engineering soil slope and a construction method thereof.
Background
With the continuous development of the traffic engineering construction in China, more and more engineering soil slopes appear. At the same time, the problem of a large number of engineering soil slopes is also involved, with landslide failure being the most common form of failure. The liquefaction of the side slope caused by the earthquake is also an important cause of landslide damage, the unstable collapse of the roadbed and the side slope can be induced, the traffic is blocked, and the serious landslide collapse of the side slope can cause personal casualties and major property loss.
The existing technology for treating the pile foundation by the aid of the earthquake liquefaction mainly adopts a combined form of gravel piles and anti-slide piles, and comprises the following specific steps: the gravel piles are used as drainage channels in the filled areas, so that the hyperstatic pore water pressure generated by the earthquake is reduced, and the purpose of preventing and preliminarily treating engineering soil slope liquefaction caused by the earthquake is achieved; and meanwhile, the filling slope toe is supported and blocked by adopting the anti-skidding piles, the piles penetrate through the liquefied soil layer and are inserted into the stabilized soil layer to a certain depth, and a certain treatment effect is achieved on the liquefied landslide of the soil layer. However, the traditional pile foundation technology only carries out prevention and preliminary treatment on the liquefaction of the engineering soil slope earthquake, has low prevention and treatment separation efficiency, and cannot deeply and comprehensively treat the liquefaction landslide damage of the engineering soil slope caused by strong earthquake.
Therefore, in order to prevent and treat the liquefaction damage of the engineering soil slope caused by the earthquake in time and solve the problem of prevention and treatment of the landslide damage of the engineering soil slope under different earthquake magnitudes, a pile foundation for the liquefaction landslide damage of the engineering soil slope with combination of automatic prevention and treatment and high efficiency is urgently needed.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a pile foundation for preventing and treating earthquake liquefaction landslide of an engineering soil slope and a construction method thereof.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the invention provides a pile foundation for preventing and controlling earthquake liquefaction landslide of an engineering soil slope on one hand, which comprises a pile foundation main body and an automatic earthquake liquefaction prevention and control system; the pile foundation main body comprises a pile cap, a hollow concrete pile foundation, a drain pipe, a grouting guide pipe and a grouting pipe;
the pile cap is provided with a grouting pipe passage hole, a drainage pipe interface, a sensor interface panel and a sealing plug, the pile cap is hermetically connected with the hollow concrete pile foundation, and the sealing plug is used for sealing the grouting pipe passage hole;
the hollow concrete pile foundation is of a concrete structure with a circular top view, four rows of anti-filtration water guide holes are symmetrically and uniformly arranged on the surface of the hollow concrete pile foundation along the axial direction and are orthogonally distributed on a radial section, two rows of one-way grouting holes are symmetrically and uniformly arranged, the four rows of anti-filtration water guide holes and the two rows of one-way grouting holes are distributed on the cross section of the hollow concrete pile foundation in a staggered mode, the anti-filtration water guide holes are reserved channel holes of an anti-filtration water guide pipe, and the one-way grouting holes are reserved channel holes of the one-way grouting pipe;
the drainage pipe consists of a reverse-filtering water guide pipe and a drainage pipe main body, four rows of reverse-filtering water guide holes are symmetrically and uniformly arranged on the drainage pipe main body along the axial direction and are orthogonally distributed on a radial section, two rows of one-way grouting holes are symmetrically and uniformly arranged, and meanwhile, the four rows of reverse-filtering water guide holes and the two rows of one-way grouting holes are distributed on the cross section of the drainage pipe in a staggered manner; the anti-filtration water guide hole and the one-way grouting hole in the drain pipe main body respectively correspond to the anti-filtration water guide hole and the one-way grouting hole in the hollow concrete pile foundation; the mouth of the reverse filtration water guide pipe is provided with a drainage plate, the surface of the reverse filtration water guide pipe is provided with a reverse filtration layer, and the mouth of the reverse filtration water guide pipe is flush with the outer surface of the pile foundation and is mechanically connected with the drainage pipe main body;
the grouting guide pipe consists of a grouting guide pipe main body and one-way grouting pipes, two rows of one-way grouting holes are uniformly arranged on the grouting guide pipe main body along the axial symmetry direction, the one-way grouting holes in the grouting guide pipe correspond to the one-way grouting holes in the hollow concrete pile foundation, and the pipe orifices of the one-way grouting pipes are flush with the outer surface of the pile foundation;
the grouting pipe comprises a grouting pipe main body, an electromagnet grouting end and an iron limiting end, wherein the grouting pipe main body extends into the grouting guide pipe main body, the end part of the grouting pipe main body is fixedly connected with the electromagnet grouting end annularly wrapping a first rubber ring in a sleeve mode, and the iron limiting end annularly wrapping a second rubber ring is arranged between the electromagnet grouting end and the front end face of the grouting guide pipe main body; the grouting guide pipe main body is used as a movable channel of the electromagnet grouting end and the iron limiting end, a grouting space communicated with the grouting pipe main body is formed between the electromagnet grouting end and the iron limiting end, and the electromagnet grouting end has magnetism after being electrified, so that the position of the iron limiting end is controlled to realize grouting positioning for treating the earthquake liquefaction landslide of the engineering soil slope; when the pile foundation is in a non-working state, the electromagnet grouting end and the iron limiting end can reach the foremost end of the pile foundation;
the automatic earthquake liquefaction prevention system comprises a pore pressure sensor, an acquisition instrument, an alarm and a water pump; the pore pressure sensor consists of a pore pressure sensor probe, sensor leads and a channel thereof, wherein the pore pressure sensor probe is uniformly distributed in the anti-filtration water guide hole on the surface of the hollow concrete pile foundation in a criss-cross manner and is connected with the sensor leads, and the sensor leads are connected with a sensor interface panel through the channel thereof; the sensor interface panel is connected with the acquisition instrument through a lead, the acquisition instrument, the alarm and the water pump are sequentially connected, the water discharge pipe interface is communicated with a water discharge pipe, the water discharge function of the automatic earthquake liquefaction prevention and control system can be realized, the acquisition instrument reads the measured pore water pressure, and when the measured data of the acquisition instrument is obviously increased compared with the original pore pressure of the same soil layer, the alarm gives an alarm and uses the water pump to discharge water, so that the automatic earthquake liquefaction prevention and preliminary treatment are realized; the alarm stores the displacement early warning value of the actual engineering side slope, and when the side slope is too large in deformation or too fast in deformation speed and exceeds the early warning value, the alarm gives an alarm and utilizes the pressure grouting device to perform grouting in the pile foundation, so that the depth control of the earthquake liquefaction of the engineering soil side slope is realized.
Further, the pile foundation is applied to the prevention and treatment of the gradual fluidity engineering soil slope landslide and the gradual plasticity engineering soil slope landslide; soil body damage characteristics of the gradual fluidity engineering soil slope landslide and the gradual plasticity engineering soil slope landslide are obtained by performing a dynamic triaxial test of seismic liquefaction on a sample with consistency and porosity ratio consistent with those of a filling slope; the following four figures are sequentially arranged according to the test data: (a) axial strain-cycle number plot; (b) hyperstatic pore water pressure-cycle number diagram; (c) offset stress-axial strain diagram; (d) offset stress — mean effective stress map;
the soil body destruction of the gradual fluidity engineering soil slope landslide is generated after the soil body strength is softened under the earthquake cycle dynamic load, and is characterized in that:
according to the axial strain-cycle number diagram, the axial strain does not vibrate up and down obviously in the initial several cycles of the action of the cyclic dynamic load; after the periodic action of a plurality of circulating power loads, the axial strain of the sample vibrates up and down along with the circulating times of the power loads, and the vibration amplitude is continuously increased until the soil body of the sample is subjected to circulating liquefaction damage;
according to the hyperstatic pore water pressure-cycle times diagram, the hyperstatic pore pressure is vibrated and increased under the action of a cyclic power load, and when the maximum value of the hyperstatic pore water pressure reaches or approaches to an effective confining pressure value, the soil body is subjected to cyclic liquefaction damage; in a plurality of cycle periods before the soil body is subjected to cyclic liquefaction damage, the amplitude of the hyperstatic pore water pressure oscillation is subjected to mutation;
according to an offset stress-axial strain diagram, at the initial stage of the action of the cyclic dynamic load, the axial strain is basically kept unchanged, and the offset stress oscillates up and down; after the periodic action of a plurality of cyclic power loads, the axial strain of the sample vibrates along with the vertical vibrating bias stress until the soil body of the sample is subjected to cyclic liquefaction damage;
according to the bias stress-average effective stress diagram, under the action of cyclic power load, the average effective stress is continuously reduced along with the bias stress oscillating up and down; when the oscillation minimum value of the average effective stress reaches or even is smaller than a zero value, the soil body is subjected to cyclic liquefaction damage.
The soil body destruction characteristic of the progressive plastic engineering soil slope landslide is that under the action of earthquake cycle power load, soil body plastic deformation is accumulated until deformation is overlarge, but obvious destruction does not occur, and the soil body destruction characteristic is as follows:
according to an axial strain-cycle number diagram, under the action of a cycle power load, the axial strain of the sample is vibrated and increased along with the cycle number of the power load until the axial strain of the sample is too large and the soil body is subjected to plastic damage;
according to the hyperstatic pore water pressure-cycle times diagram, under the action of cyclic power load, the hyperstatic pore water pressure shock is increased, the amplitude of the hyperstatic pore water pressure shock is also increased, and the shock maximum value of the hyperstatic pore water pressure is close to the effective confining pressure value continuously until the axial strain of the sample is overlarge and the soil body is subjected to plastic damage;
according to the offset stress-axial strain diagram, under the action of cyclic power load, the axial strain of the sample is continuously increased along with the offset stress of up-down oscillation until the axial strain of the sample is overlarge and can not be recovered, and the soil body is subjected to plastic damage;
according to the bias stress-average effective stress diagram, under the action of cyclic power load, the average effective stress is continuously reduced along with the bias stress oscillating up and down; the maximum value of the average effective stress has no obvious vibration reduction amplitude change, but the minimum value of the average effective stress has a remarkable vibration reduction trend; when the oscillation minimum value of the average effective stress reaches or is even smaller than a zero value, the axial strain of the sample is overlarge, and the soil body is subjected to plastic damage.
Furthermore, the drain pipe interface and the sensor interface panel adopt a mechanical sealing interface technology to ensure that the drain pipe interface and the sensor interface panel are completely sealed.
Furthermore, the mouth of pipe of the reverse-filtering water guide pipe is provided with a water discharge plate, the surface of the reverse-filtering water guide pipe is provided with a reverse-filtering layer, only water flows but soil particles do not flow, and the loss of the particles of the rock-soil layer of the pile foundation in the drainage process is prevented.
Furthermore, the tail part of the one-way grouting pipe is provided with a one-way valve which ensures that only the slurry can flow out but not flow in, namely the slurry can enter a seepage damage area through the one-way valve for reinforcement, and seepage water backflow caused by soil layer particle loss or liquefaction can be prevented.
Furthermore, the electromagnet grouting end is attracted to the iron limiting end after being electrified, the grouting pipe main body and the two ends are pulled, grouting limiting can be achieved, and the grouting pipe main body is pulled after being powered off, so that a sufficient grouting space is reserved between the two ends.
Furthermore, the number and the diameter of the reverse filtering water guide holes and the one-way grouting holes can be properly increased or decreased according to the diameter of the pile foundation in specific engineering, and the specifications of the reverse filtering water guide pipes and the one-way grouting pipes correspond to the corresponding reserved channel holes.
The invention also provides a construction method of a pile foundation for preventing and controlling the earthquake liquefaction landslide of the engineering soil slope, which comprises the following steps:
(1) and (3) carrying out pile position measurement and placement according to a plan view of an engineering site and coordinate control points, determining the pile position, driving a short steel bar at the center of the pile position, coating red paint, and repeatedly measuring the pile position after positioning.
(2) The pore pressure sensor detection group is installed in the prefabricated pile foundation, a pore pressure sensor probe and a pore pressure test surface are tangent to the outer side wall of the hollow concrete pile foundation, the pore pressure sensor probe and the pore pressure test surface are fixedly installed in the reverse filtration water guide hole, and the pore pressure sensor probe, the sensor interface panel, the acquisition instrument and the alarm are connected through wires.
(3) The pile foundation is prefabricated by static pressure by a pile pressing machine, and the pile foundation has a certain depth in a stable soil layer to enhance the earthquake liquefaction resistance of the pile foundation.
(4) After the pile foundation is installed, a proper amount of air pressure is added into the pipe to clean the hole of the one-way grouting pipe and the reverse filtering water guide pipe, so that the reverse filtering layer and the one-way valve are prevented from being blocked by soil particles to influence the working effect of the device.
(5) The data measured by the pore pressure sensor probe are read by the collector, when the data measured by the collector is obviously increased compared with the original pore pressure of the same soil layer, the alarm gives an alarm and utilizes the water pump to drain water, water carrying soil particles enters the anti-filtration water guide holes on the surface of the pile foundation, the soil particles are left on the soil layer through the anti-filtration layer and the drainage plate, and meanwhile, the water after the anti-filtration is discharged out of the geotechnical layer through the drainage pipe, so that the prevention and the preliminary treatment of the earthquake liquefaction of the engineering soil slope are realized.
(6) And (3) monitoring the slope displacement by adopting a conventional displacement monitoring method, calculating to obtain an actual engineering slope displacement early warning value according to relevant specifications, inputting the early warning value into an alarm, and when the slope deformation is too large or the deformation speed is too high and exceeds the early warning value, giving an alarm and entering a grouting step.
(7) Opening a sealing plug on a pile cap, electrifying a grouting end of an electromagnet, sucking an iron limiting end, pulling a grouting pipe to enable a grouting pipe main body to drive two ends to reach positions needing grouting, then powering off, pulling the grouting pipe to enable the two ends to be separated, ensuring that an enough grouting space exists between the two ends, grouting into a pile foundation by using a pressure grouting device, cleaning holes before final setting after slurry is initially set, preventing the slurry from blocking the pipe orifice, and realizing deep treatment of the earthquake liquefaction of the engineering soil side slope.
Furthermore, in the step (2), considering the construction cost, pore pressure sensor probes are uniformly distributed in the part of the reverse filtration water guide holes on the surface of the hollow concrete pile foundation in a criss-cross mode.
Furthermore, in the step (3), the precast pile is vertically driven by static force, so that the phenomenon that the original mechanical property of the soil body is changed by power driving to cause artificial soil layer liquefaction is avoided.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention is a reconstruction innovation of the traditional pile foundation, combines the prevention drainage and the grouting treatment into an organic whole, and the prevention drainage and the grouting treatment are both positioned in the pile foundation and are independent from each other without mutual interference, thereby realizing the prevention and control integration.
2. The invention adopts an automatic earthquake liquefaction prevention system, the acquisition instrument can automatically read and store the pore water pressure data of the side slope liquefied soil layer area monitored by the pore pressure sensor, the alarm carries out early warning and processing on the data of the acquisition instrument, when the pore pressure rises to an early warning value, the alarm gives an alarm and starts the water pump to pump water, the pore pressure is reduced in time, and the risk of soil layer liquefaction is eliminated.
3. The data obtained by the automatic monitoring has small error, and the method has the advantages of low cost, wide coverage, high data reliability and the like, and has wide engineering application prospect.
4. The invention adopts the grouting limiter to carry out positioning grouting, improves the accuracy of grouting reinforcement and effectively reinforces the liquefied soil layer.
5. The static pile pressing method is adopted, so that manual soil layer liquefaction caused by changing the original mechanical property of the soil body by power inserting and beating is avoided; static force pile press has a plurality of advantages simultaneously: low noise, no pollution and no vibration; the construction speed is high, the construction period is short, and the construction cost is reduced; the pile feeder is well matched with the contact surface of the pile head of the engineering pile, and the adverse conditions of left-right shaking and the like in the pile driving process are avoided.
6. The pile foundation and the construction method thereof can be used for deeply treating progressive fluidity engineering soil slope landslide damage and progressive plasticity engineering soil slope landslide damage.
Drawings
FIG. 1 is a schematic diagram of landslide of an engineering soil slope caused by an earthquake according to the present invention;
FIG. 2(a) is a schematic axial strain (ordinate) -cycle number (abscissa) for a progressive fluidity engineering soil slope landslide type of the present invention;
FIG. 2(b) is a schematic diagram of the hyperstatic pore water pressure (ordinate) -cycle number (abscissa) of the progressive fluidity engineering soil slope landslide type of the present invention;
FIG. 2(c) is a schematic representation of the offset stress (ordinate) -axial strain (abscissa) for a progressive fluidity engineered soil slope landslide version of the present invention;
FIG. 2(d) is a schematic diagram of the offset stress (ordinate) -mean effective stress (abscissa) of the progressive fluidity engineering soil slope landslide type of the present invention;
FIG. 3(a) is a schematic representation of axial strain (ordinate) -cycle number (abscissa) for a progressive plastic engineering soil slope landslide type of the present invention;
FIG. 3(b) is a schematic diagram of the hyperstatic pore water pressure (ordinate) -cycle number (abscissa) of the progressive plasticity engineering soil slope landslide type according to the invention;
FIG. 3(c) is a schematic representation of the partial stress (ordinate) -axial strain (abscissa) of the progressive plastic engineering soil slope landslide type of the present invention;
FIG. 3(d) is a schematic diagram of the partial stress (ordinate) -mean effective stress (abscissa) of the progressive plastic engineering soil slope landslide type of the present invention;
FIG. 4 is a side view of the pile foundation for the earthquake liquefaction landslide control of the engineering soil slope of the present invention;
FIG. 5 is a top view of pile cap of pile foundation for prevention and treatment of earthquake liquefaction landslide of engineering soil slope;
FIG. 6 is a section of FIG. AA;
FIG. 7 is a section of FIG. BB;
FIG. 8 is a sectional view of the pile foundation positioning grouting process;
wherein: a pile cap 1, a grouting pipe passage hole 1-1, a drain pipe interface 1-2, a sensor interface panel 1-3, a sealing plug 1-4, a hollow concrete pile foundation 2, a reverse filtration water guide hole 2-1, a one-way grouting hole 2-2, a drain pipe 3, a reverse filtration water guide pipe 3-1, a reverse filtration layer 3-1-1 and a drain board 3-1-2, the device comprises a drain pipe main body 3-2, a grouting guide pipe 4, a grouting guide pipe main body 4-1, a one-way grouting pipe 4-2, a one-way valve 4-2-1, a grouting pipe 5, a grouting pipe main body 5-1, an electromagnet grouting end 5-2, a first rubber ring 5-2-1, an iron limiting end 5-3, a second rubber ring 5-3-1 and a hole pressure sensor probe 6.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
The invention provides a pile foundation for preventing and treating an earthquake liquefaction landslide of an engineering soil slope, which is mainly applied to the prevention and treatment of a gradual fluidity engineering soil slope landslide and a gradual plasticity engineering soil slope landslide.
As shown in fig. 1, which is a schematic diagram of landslide of an engineering soil slope caused by an earthquake, under the action of earthquake cycle power, a road surface close to the slope and a soil layer of the slope slide along a curved slip surface direction, so that the road surface and the slope collapse, thereby generating landslide.
Soil body destruction characteristics of the gradual fluidity engineering soil slope landslide and the gradual plasticity engineering soil slope landslide are obtained by carrying out dynamic triaxial test of seismic liquefaction on a sample with the compactness and the porosity ratio consistent with those of the filling slope; the following four figures are sequentially arranged according to the test data: (a) axial strain (ordinate) -cycle number (abscissa) plots, as shown in fig. 2(a), 3 (a); (b) hyperstatic pore water pressure (ordinate) -cycle number (abscissa) as shown in fig. 2(b), fig. 3 (b); (c) the offset stress (ordinate) -axial strain (abscissa) as shown in fig. 2(c), 3 (c); (d) bias stress (ordinate) -mean effective stress (abscissa) as shown in fig. 2(d), fig. 3 (d).
Firstly, soil body destruction of gradual fluidity engineering soil slope landslide occurs after soil body strength is softened under earthquake cycle dynamic load, and the method is specifically characterized in that:
as shown in fig. 2(a) axial strain (ordinate) -cycle number (abscissa) diagram, the axial strain does not oscillate up and down significantly during the initial periods of the cyclic dynamic loading; after the periodic action of a plurality of circulating power loads, the axial strain of the sample vibrates up and down along with the circulating times of the power loads, and the vibration amplitude is continuously increased until the soil body of the sample is subjected to circulating liquefaction damage;
as shown in a diagram of hyperstatic pore water pressure (ordinate) -cycle frequency (abscissa) in fig. 2(b), the hyperstatic pore pressure vibrates and increases under the action of a cyclic power load, and when the maximum value of the hyperstatic pore water pressure reaches (or approaches) an effective confining pressure value, the soil body is subjected to cyclic liquefaction damage; in a plurality of cycle periods before the soil body is subjected to cyclic liquefaction damage, the amplitude of the hyperstatic pore water pressure oscillation is subjected to mutation;
as shown in the graph of the offset stress (ordinate) -axial strain (abscissa) in fig. 2(c), in the initial stage of the action of the cyclic dynamic load, the axial strain is basically kept unchanged, and the offset stress oscillates up and down; after the periodic action of a plurality of cyclic power loads, the axial strain of the sample vibrates along with the vertical vibrating bias stress until the soil body of the sample is subjected to cyclic liquefaction damage;
as shown in fig. 2(d), the offset stress (ordinate) -the average effective stress (abscissa), under the action of the cyclic dynamic load, the average effective stress is continuously reduced along with the offset stress of the up-and-down oscillation; when the oscillation minimum value of the average effective stress reaches or even is smaller than a zero value, the soil body is subjected to cyclic liquefaction damage.
The soil body destruction characteristic of the gradual plastic engineering soil slope landslide is that under the action of earthquake cycle power load, the soil body plastic deformation is accumulated until the deformation is overlarge, but obvious destruction does not occur, and the soil body destruction characteristic is as follows:
as shown in fig. 3(a), axial strain (ordinate) -cycle number (abscissa), under the action of a cyclic dynamic load, the axial strain of the sample is oscillated and increased along with the cycle number of the dynamic load until the axial strain of the sample is too large, and the soil body is plastically damaged;
as shown in a diagram of hyperstatic pore water pressure (ordinate) -cycle frequency (abscissa) in fig. 3(b), under the action of a cyclic power load, the hyperstatic pore water pressure shock is increased, the amplitude of the hyperstatic pore water pressure shock is also increased continuously, and the maximum value of the hyperstatic pore water pressure shock is close to the effective confining pressure value continuously until the axial strain of the sample is too large, and the soil body is subjected to plastic damage;
as shown in fig. 3(c), the offset stress (ordinate) -axial strain (abscissa) diagram, under the action of the cyclic dynamic load, the axial strain of the sample is continuously increased along with the offset stress of the up-and-down oscillation until the axial strain of the sample is too large and can not be recovered, and the soil body is subjected to plastic failure;
as shown in the graph of the bias stress (ordinate) -the average effective stress (abscissa) in fig. 3(d), under the action of the cyclic dynamic load, the average effective stress is continuously reduced along with the bias stress oscillating up and down; the maximum value of the average effective stress has no obvious vibration reduction amplitude change, but the minimum value of the average effective stress has a remarkable vibration reduction trend; when the oscillation minimum value of the average effective stress reaches or is even smaller than a zero value, the axial strain of the sample is overlarge, and the soil body is subjected to plastic damage.
The invention provides a pile foundation for preventing and treating earthquake liquefaction landslide of an engineering soil slope, which comprises a pile foundation main body and an automatic earthquake liquefaction prevention and treatment system; as shown in fig. 4-7, the pile foundation body comprises a pile cap 1, a hollow concrete pile foundation 2, a drain pipe 3, a grouting guide pipe 4 and a grouting pipe 5;
as shown in fig. 5, a pile cap 1 is provided with a grouting pipe passage hole 1-1, a drain pipe interface 1-2, a sensor interface panel 1-3 and a sealing plug 1-4, the pile cap 1 and a hollow concrete pile foundation 2 are connected in a welding and sealing manner, and the sealing plug 1-4 is used for sealing the grouting pipe passage hole 1-1;
the hollow concrete pile foundation 2 is of a circular ring-shaped concrete structure in a top view, four rows of reverse-filtration water guide holes 2-1 are symmetrically and uniformly arranged on the surface of the hollow concrete pile foundation 2 along the axial direction, the four rows of one-way grouting holes 2-2 are symmetrically and uniformly arranged, the four rows of reverse-filtration water guide holes 2-1 and the two rows of one-way grouting holes 2-2 are distributed on the cross section of the hollow concrete pile foundation 2 in a staggered mode, the reverse-filtration water guide holes 2-1 serve as reserved channel holes of a reverse-filtration water guide pipe 3-1, and the one-way grouting holes 2-2 serve as reserved channel holes of a one-way grouting pipe 4-2;
as shown in fig. 6, the drain pipe 3 is composed of a reverse filtering water guide pipe 3-1 and a drain pipe main body 3-2, four rows of reverse filtering water guide holes 2-1 are symmetrically and uniformly arranged on the drain pipe main body 3-2 along the axial direction and are orthogonally distributed on a radial section, two rows of one-way grouting holes 2-2 are symmetrically and uniformly arranged, and meanwhile, the four rows of reverse filtering water guide holes 2-1 and the two rows of one-way grouting holes 2-2 are distributed on the cross section of the drain pipe 3 in a staggered manner; the reverse filtration water guide hole 2-1 and the one-way grouting hole 2-2 on the drain pipe main body 3-2 correspond to the reverse filtration water guide hole 2-1 and the one-way grouting hole 2-2 on the hollow concrete pile foundation 2 respectively; the mouth of the reverse filtration water guide pipe 3-1 is provided with a drainage plate 3-1-2, the surface of the reverse filtration water guide pipe is provided with a reverse filtration layer 3-1-1, and the mouth of the reverse filtration water guide pipe is flush with the outer surface of the pile foundation and is mechanically connected with a drainage pipe main body 3-2;
as shown in fig. 7, the grouting guide pipe 4 is composed of a grouting guide pipe main body 4-1 and a one-way grouting pipe 4-2, two rows of one-way grouting holes 2-2 are uniformly arranged on the grouting guide pipe main body 4-1 along the axial symmetry, the one-way grouting holes 2-2 on the grouting guide pipe 4 correspond to the one-way grouting holes 2-2 of the hollow concrete pile foundation 2, and the pipe orifice of the one-way grouting pipe 4-2 is flush with the outer surface of the pile foundation;
as shown in fig. 6 and 7, the grouting pipe 5 comprises a grouting pipe main body 5-1, an electromagnet grouting end 5-2 and an iron limiting end 5-3, the grouting pipe main body 5-1 extends into the grouting guide pipe main body 4-1, the end part of the grouting pipe main body is fixedly connected with the electromagnet grouting end 5-2 annularly wrapped with a first rubber ring 5-2-1 in a sleeve manner, the iron limiting end 5-3 annularly wrapped with a second rubber ring 5-3-1 is arranged between the electromagnet grouting end 5-2 and the front end surface of the grouting guide pipe main body 4-1, and the rubber ring enhances the sealing effect between the surface of the grouting stopper (consisting of the electromagnet grouting end 5-2 and the iron limiting end 5-3) and the inner wall of the grouting guide pipe; the grouting guide pipe main body 4-1 is used as a movable channel of an electromagnet grouting end 5-2 and an iron limiting end 5-3, a grouting space communicated with the grouting pipe main body 5-1 is formed between the electromagnet grouting end 5-2 and the iron limiting end 5-3, and the electromagnet grouting end 5-2 has magnetism after being electrified, so that the position of the iron limiting end 5-3 is controlled to realize grouting positioning for treating the earthquake liquefaction landslide of the engineering soil side slope; in a non-working state, the electromagnet grouting end 5-2 and the iron limiting end 5-3 can reach the foremost end of the pile foundation;
the automatic earthquake liquefaction prevention system comprises a pore pressure sensor, an acquisition instrument, an alarm and a water pump; the pore pressure sensor consists of a pore pressure sensor probe 6, sensor leads and a channel thereof, wherein the pore pressure sensor probe 6 is uniformly distributed in the reverse filtration water guide hole 2-1 on the surface of the hollow concrete pile foundation 2 in a criss-cross manner and is connected with the sensor leads, and the sensor leads are connected with a sensor interface panel 1-3 through the channel thereof; the sensor interface panel 1-3 is connected with an acquisition instrument through a lead, the acquisition instrument, an alarm and a water pump are sequentially connected, the water discharge pipe interface 1-2 is communicated with a water discharge pipe 3, the drainage function of the automatic earthquake liquefaction prevention system can be realized, the acquisition instrument can read the measured pore water pressure, when the measured data of the acquisition instrument is obviously increased compared with the original pore pressure of the same soil layer, the alarm gives an alarm and utilizes the water pump to drain water, and the automatic earthquake liquefaction prevention and primary treatment are realized; the alarm stores the displacement early warning value of the actual engineering side slope, and when the side slope is too large in deformation or too fast in deformation speed and exceeds the early warning value, the alarm gives an alarm and utilizes the pressure grouting device to perform grouting in the pile foundation, so that the depth control of the earthquake liquefaction of the engineering soil side slope is realized.
Specifically, the drainage pipe interface 1-2 and the sensor interface panel 1-3 adopt a mechanical sealing interface technology to ensure that the drainage pipe interface 1-2 and the sensor interface panel 1-3 are completely sealed.
Specifically, the opening of the reverse filtering water guide pipe 3-1 is provided with a drain board 3-1-2, the surface of the reverse filtering water guide pipe is provided with a reverse filtering layer 3-1-1, only water and soil blocking particles are passed through, and the loss of rock and soil layer particles in the drainage process of the pile foundation is prevented.
Specifically, the tail part of the one-way grouting pipe 4-2 is provided with a one-way valve 4-2-1, and the one-way valve 4-2-1 ensures that only the slurry can flow out but not flow in, namely, the slurry can enter a seepage damage area through the one-way valve 4-2-1 for reinforcement, and seepage water backflow caused by soil layer particle loss or liquefaction can be prevented.
Specifically, the electromagnet grouting end 5-2 is attracted to the iron limiting end 5-3 after being electrified, the grouting pipe main body 5-1 and the two ends are pulled, grouting limiting can be achieved, and the grouting pipe main body 5-1 is pulled after power is off, so that a sufficient grouting space is reserved between the two ends.
Specifically, the number and diameter of the reverse filtering water guide holes 2-1 and the one-way grouting holes 2-2 can be properly increased or decreased according to the diameter of the pile foundation in specific engineering, and the specifications of the reverse filtering water guide pipe 3-1 and the one-way grouting pipe 4-2 correspond to the corresponding reserved channel holes.
The concrete test steps for obtaining the soil body destruction characteristics of the gradual liquidity engineering soil slope landslide and the gradual plasticity engineering soil slope landslide by the dynamic triaxial test of seismic liquefaction of the sample consistent with the compactness and the porosity ratio of the filling slope are given below, but not limited to:
(1) firstly, sleeving a rubber film on a sample mounting bottom cap of a GDS movable triaxial sample base, fixing the rubber film by using a rubber ring, tightly connecting and fixing double-petal molds of an auxiliary tool prepared by the GDS movable triaxial sample on the GDS movable triaxial sample mounting bottom cap to ensure that the double-petal molds clamp the rubber film on the sample mounting bottom cap, flatly pasting the rubber film on the inner wall of the double-petal molds, and specifically, applying suction of about-20 kPa through a suction nozzle of the double-petal molds to ensure that the rubber film is tightly pasted on the inner wall of the double-petal molds; weighing dried filling side slope soil samples with corresponding mass according to the design filling density of the engineering side slope and the volume of the GDS dynamic triaxial sample, and uniformly pouring a sample soil body by a layered filling method; after the sample is poured, horizontally installing a sample top cap on the top of the sample; tightly sleeving a sample top cap with a rubber film, and fixing with a rubber ring; connecting a carbon dioxide gas tank with a sample bottom communication valve on a GDS dynamic triaxial sample base, connecting the bottom of a negative pressure pre-saturation accessory after water injection with a sample top communication valve, and connecting the top of the negative pressure pre-saturation accessory with a vacuum pump; closing a sample bottom communicating valve on a GDS movable triaxial sample base, and slowly opening a vacuum pump and a sample top communicating valve in sequence, wherein the negative pressure of the vacuum pump is kept at-20 kPa; after the sample is kept upright under the condition of stable negative pressure, the double-section mold is dismantled, and the preliminary preparation step of the sample is completed;
(2) after the double-valve mold is dismantled, continuously keeping the negative pressure of the vacuum pump at-20 kPa; opening a communicating valve at the bottom of the sample, and adjusting a valve of a carbon dioxide gas tank to make bubbles in the negative pressure pre-saturation fitting uniformly and slowly emerge; continuously and slowly introducing carbon dioxide gas into the sample for 30min, and then closing a valve at the bottom of the sample, which is communicated with the valve and a carbon dioxide gas tank; disconnecting the carbon dioxide gas tank from the sample bottom communication valve, and connecting the waterless pre-saturation fitting with the sample bottom communication valve; after sufficient non-aqueous water is injected into the non-aqueous pre-saturation fitting, a communicating valve at the bottom of the sample is slowly opened, the non-aqueous water in the non-aqueous pre-saturation fitting is continuously and slowly injected into the sample under the action of stable negative pressure, and bubbles are uniformly and slowly emitted from the negative pressure pre-saturation fitting; after the bubbles in the negative pressure pre-saturation fitting completely disappear, continuously injecting the non-air water for 30min, then simultaneously closing the bottom communicating valve and the top communicating valve of the sample, and then closing the vacuum pump to complete the pre-saturation step of the sample; wherein, the negative pressure pre-saturation fitting is required to ensure the air tightness; the non-aqueous water in the non-aqueous pre-saturation fitting can be replenished as required during the process of introducing the non-aqueous water to the sample.
(3) Hermetically installing a GDS movable triaxial confining pressure cover on a GDS movable triaxial sample base, and filling airless water into the confining pressure cover; connecting a confining pressure communicating valve on a GDS movable triaxial sample base with a confining pressure controller, and connecting a sample bottom communicating valve and a sample top communicating valve with the same back pressure controller; according to the permeability characteristic of a slope soil sample under the condition of engineering slope design filling density, a reasonable sample back pressure and confining pressure loading program is set in a GDS control system, the back pressure and confining pressure loading rates in the sample saturation process are the same, and the confining pressure is always 10kPa higher than the back pressure; opening a sample bottom communication valve, a sample top communication valve and a confining pressure communication valve, automatically regulating and controlling a confining pressure controller and a back pressure controller through a GDS control system, and applying confining pressure and back pressure to the sample according to a set back pressure and confining pressure loading program until a saturated confining pressure P is reached0And saturation back pressure u0(ii) a Keeping the sample for a period of time under the conditions of saturated confining pressure and saturated back pressure, and finishing the step of back pressure saturation of the sample when the GDS control system detects that the pore water pressure coefficient B of the sample is more than or equal to 0.98; closing the bottom communicating valve of the sample and the top communicating valve of the sample, so that the preparation and saturation of the sample are finished;
specifically, the loading rate of the back pressure and the confining pressure set in the back pressure and confining pressure loading program can be realized by a back pressure loading pre-experiment; the steps of the back pressure loading pre-experiment are as follows: firstly, connecting a confining pressure communicating valve with a confining pressure controller, connecting a sample top communicating valve with a back pressure controller, closing the sample bottom communicating valve, opening a GDS control system, and reading data of a sample bottom pore water pressure sensor in real time through the GDS control system; secondly, slowly increasing the confining pressure of the sample to 20kPa at a constant speed by a confining pressure controller, applying 10kPa back pressure to the top of the sample by a back pressure controller and a communicating valve at the top of the sample, and observing the acquired pore water pressure data at the bottom of the sample; recording the time interval T(s) for increasing the pore water pressure value at the bottom of the sample from 0kPa to 10kPa, and determining the loading rate of the back pressure and the confining pressure to be 10/T (kPa/s);
the saturated confining pressure P0And saturation back pressure u0Typically 310kPa and 300kPa, respectively; the setting of the saturated confining pressure, the saturated back pressure and the application time of the saturated confining pressure and the saturated back pressure ensures that the pore water pressure coefficient B of the sample can meet the requirement of sample saturation, namely the pore water pressure coefficient B is more than or equal to 0.98.
(4) Determining the axial pressure P of the sample according to the hydrogeological conditions of the engineering side slope and the buried depth conditions of the test soil samplezConfining pressure PwAnd pore water pressure usFrom which the effective stress of the specimen, including the effective axial pressure σ, will be obtainedz’＝Pz-usAnd effective confining pressure σw’＝Pw-us(ii) a A back pressure controller is arranged to keep the back pressure value of the sample to be saturated back pressure u all the time in the sample consolidation process0Opening a communicating valve at the top of the sample when the value is unchanged; according to the principle of effective stress control, at saturation confining pressure P0And saturation back pressure u0On the basis of the method, axial pressure and confining pressure are applied to the sample according to a set axial pressure and confining pressure loading program, and axial deformation and volume change (consolidation drainage volume) of the sample are collected and recorded until consolidation axial pressure and consolidation confining pressure are achieved; the sample is kept for a period of time under the conditions of consolidation axial pressure and consolidation confining pressure, and the axial deformation and the volume change (consolidation drainage volume) of the sample are collected and recorded) The consolidation of the sample is completed in the initial shear stress state;
specifically, the principle of effective stress control means that the effective stress of the solidified sample is consistent with the effective stress of the engineering slope field where the sample is located; the loading rate of the axial pressure and the confining pressure set in the axial pressure and confining pressure loading program is consistent with the loading rate of the back pressure and the confining pressure adopted in the sample back pressure saturation process; consolidation axial compression value of u0+σz'; consolidation confining pressure value of u0+σw'; the judgment standard for finishing consolidation of the sample in the initial shear stress state is as follows: under the conditions of consolidation axial pressure and consolidation confining pressure, the volume deformation of the sample within 1 hour is less than 0.05 percent, and the pore water pressure value measured by the sample is equal to the saturation back pressure u0The value is obtained.
(5) According to the initial shear stress tau of the engineering slope test soil samplesApplying the earthquake cycle power load to the sample by setting a power loading program, and automatically recording and storing the axial deformation, the volume deformation, the axial pressure, the confining pressure and the pore water pressure change data of the sample by a GDS dynamic triaxial data acquisition device; in particular, the initial shear stress τ s1/2 being the difference between the consolidation axial pressure and the consolidation confining pressure; the equilibrium position of the seismic cyclic dynamic load applied to the test specimen is at the initial bias stress qsAt a value; the initial bias stress qsThe difference value of the consolidation axial pressure and the consolidation confining pressure is obtained; the earthquake cycle power load applied to the sample by the set power loading program is an axial cycle power load; the axial pressure is earthquake cycle power load; the confining pressure is generally kept constant and has a value equal to the consolidation confining pressure.
(6) Analyzing the test result according to the collected test data, and sequentially sorting four graphs according to the axial deformation, the axial pressure, the confining pressure and the pore water pressure of the sample under the condition of earthquake cycle dynamic load so as to determine the landslide type of the engineering side slope; the axial strain is the ratio of the axial deformation to the initial height of the sample; the hyperstatic pore water pressure is the pore water pressure u and the saturation back pressure u of the sample under the condition of earthquake cycle power load0A difference of (d); the bias stress is equal to the axisThe difference between the pressure and the confining pressure; 1/3, the average effective stress is the sum of the effective axial pressure and 2 times of the effective confining pressure; the effective axial pressure is axial pressure and saturated back pressure u0A difference of (d); the effective confining pressure is confining pressure and saturated back pressure u0The difference of (a).
The invention provides a construction method of a pile foundation for preventing and treating earthquake liquefaction landslide of an engineering soil slope, which comprises the following steps:
(1) and (3) carrying out pile position measurement and placement according to a plan view of an engineering site and coordinate control points, determining the pile position, driving a short steel bar at the center of the pile position, coating red paint, and repeatedly measuring the pile position after positioning.
(2) Installing a pore pressure sensor detection group in a prefabricated pile foundation, firstly, enabling a pore pressure sensor probe 6 and a pore pressure testing surface (permeable stone) to be tangent to the outer side wall of a hollow concrete pile foundation 2, fixedly installing the pore pressure sensor probe and the pore pressure testing surface in a reverse-filtration water guide hole 2-1, and connecting the pore pressure sensor probe 6, a sensor interface panel 1-3, an acquisition instrument and an alarm through wires; considering the construction cost, pore pressure sensor probes 6 are only required to be uniformly distributed in the part of the reverse filtration water guide holes 2-1 on the surface of the hollow concrete pile foundation 2 in a criss-cross mode.
(3) The pile foundation prefabricated by the pile pressing machine is adopted, so that the pile foundation has a certain depth in a stable soil layer, the liquefaction resistance is improved, and the static pile pressing can avoid manual soil layer liquefaction caused by changing the original mechanical property of a soil body by power inserting and driving; static force pile press has a plurality of advantages simultaneously: 1. low noise, no pollution and no vibration; 2. the construction speed is high, the construction period is short, and the construction cost is reduced; 3. the pile feeder is well matched with the contact surface of the pile head of the engineering pile, and the adverse conditions of left-right shaking and the like in the pile driving process are avoided.
(4) After the pile foundation is installed, a proper amount of air pressure is added into the pipe to clean the holes of the one-way grouting pipe 4-2 and the reverse filtering water guide pipe 3-1, so that the reverse filtering layer and the one-way valve are prevented from being blocked by soil particles to influence the working effect of the device.
(5) The data measured by the pore pressure sensor probe 6 is read by the remote utilization of the collector, when the data measured by the collector is obviously increased compared with the original pore pressure of the same soil layer, the alarm gives an alarm and utilizes the water pump to drain water, water carrying soil particles enters the reverse filtering water guide hole 2-1 on the surface of the pile foundation, the soil particles are left on the soil layer through the reverse filtering layer 3-1-1 and the drainage plate 3-1-2, and meanwhile, the water after reverse filtering is discharged out of the rock-soil layer through the drainage pipe 3, so that the prevention and the primary treatment of the earthquake liquefaction of the engineering soil slope are realized.
(6) And (3) monitoring the slope displacement by adopting a conventional displacement monitoring method, calculating to obtain an actual engineering slope displacement early warning value according to relevant specifications, inputting the early warning value into an alarm, and when the slope deformation is too large or the deformation speed is too high and exceeds the early warning value, giving an alarm and entering a grouting step.
(7) As shown in fig. 8, a sealing plug 1-4 on a pile cap 1 is opened, an electromagnet grouting end 5-2 is powered on, an iron limiting end 5-3 is sucked, the grouting pipe 5 is pulled to enable a grouting pipe main body 5-1 to drive two ends to reach positions needing grouting, then power is cut off, the grouting pipe 5 is pulled to enable the two ends to be separated, a sufficient grouting space is guaranteed between the two ends, grouting is conducted into a pile foundation by using a pressure grouting device, hole cleaning is conducted before final setting after initial setting of grout, the pipe orifice is prevented from being blocked by the grout, and deep treatment of engineering soil slope earthquake liquefaction is achieved.
The foregoing description is only for the purpose of illustrating the principles of the invention and is not to be construed in any way as limiting the scope of the invention. Based on the explanations herein, those skilled in the art will be able to conceive of other embodiments of the present invention without inventive effort, which would fall within the scope of the present invention.

Claims (10)

1. A pile foundation for preventing and treating earthquake liquefaction landslide of an engineering soil slope is characterized by comprising a pile foundation main body and an automatic earthquake liquefaction prevention and treatment system;
the pile foundation main body comprises a pile cap (1), a hollow concrete pile foundation (2), a drain pipe (3), a grouting guide pipe (4) and a grouting pipe (5);
the pile cap (1) is provided with a grouting pipe passage hole (1-1), a drainage pipe interface (1-2), a sensor interface panel (1-3) and a sealing plug (1-4), the pile cap (1) is hermetically connected with the hollow concrete pile foundation (2), and the sealing plug (1-4) is used for sealing the grouting pipe passage hole (1-1);
the hollow concrete pile foundation (2) is of a circular concrete structure in a top view, four rows of anti-filtration water guide holes (2-1) are symmetrically and uniformly arranged on the surface of the hollow concrete pile foundation along the axial direction, the anti-filtration water guide holes are orthogonally distributed on a radial section, two rows of one-way grouting holes (2-2) are symmetrically and uniformly arranged, the four rows of anti-filtration water guide holes (2-1) and the two rows of one-way grouting holes (2-2) are distributed on the cross section of the hollow concrete pile foundation (2) in a staggered mode, the anti-filtration water guide holes (2-1) are reserved channel holes of an anti-filtration water guide pipe (3-1), and the one-way grouting holes (2-2) are reserved channel holes of a one-way grouting pipe (4-2);
the drainage pipe (3) consists of a reverse filtration water guide pipe (3-1) and a drainage pipe main body (3-2), four rows of reverse filtration water guide holes (2-1) are symmetrically and uniformly arranged on the drainage pipe main body (3-2) along the axial direction, the reverse filtration water guide holes are orthogonally distributed on a radial section, two rows of one-way grouting holes (2-2) are symmetrically and uniformly arranged, and meanwhile, the four rows of reverse filtration water guide holes (2-1) and the two rows of one-way grouting holes (2-2) are distributed on the cross section of the drainage pipe main body (3-2) in a staggered manner; the reverse filtration water guide hole (2-1) and the one-way grouting hole (2-2) on the drain pipe main body (3-2) respectively correspond to the reverse filtration water guide hole (2-1) and the one-way grouting hole (2-2) on the hollow concrete pile foundation (2); the pipe orifice of the reverse filtration water guide pipe (3-1) is provided with a drainage plate (3-1-2), the surface of the drainage plate is provided with a reverse filtration layer (3-1-1), the pipe orifice is flush with the outer surface of the pile foundation, and the reverse filtration water guide pipe (3-1) is mechanically connected with the drainage pipe main body (3-2);
the grouting guide pipe (4) consists of a grouting guide pipe main body (4-1) and a one-way grouting pipe (4-2), two rows of one-way grouting holes (2-2) are uniformly formed in the grouting guide pipe main body (4-1) along the axial symmetry, the one-way grouting holes (2-2) in the grouting guide pipe main body (4-1) correspond to the one-way grouting holes (2-2) in the hollow concrete pile foundation (2), and the pipe orifice of the one-way grouting pipe (4-2) is flush with the outer surface of the pile foundation;
the grouting pipe (5) consists of a grouting pipe main body (5-1), an electromagnet grouting end (5-2) and an iron limiting end (5-3), wherein the grouting pipe main body (5-1) extends into the grouting guide pipe main body (4-1), the end part of the grouting pipe main body is fixedly connected with the electromagnet grouting end (5-2) which circumferentially wraps the first rubber ring (5-2-1) in a sleeve mode, and the iron limiting end (5-3) which circumferentially wraps the second rubber ring (5-3-1) is arranged between the electromagnet grouting end (5-2) and the front end face of the grouting guide pipe main body (4-1); the grouting guide pipe main body (4-1) is used as a movable channel of the electromagnet grouting end (5-2) and the iron limiting end (5-3), a grouting space communicated with the grouting pipe main body (5-1) is formed between the electromagnet grouting end (5-2) and the iron limiting end (5-3), and the electromagnet grouting end (5-2) is magnetic after being electrified, so that the position of the iron limiting end (5-3) is controlled to realize grouting positioning for treating the earthquake liquefaction landslide of the engineering soil slope; in a non-working state, the electromagnet grouting end (5-2) and the iron limiting end (5-3) can reach the foremost end of the pile foundation;
the automatic earthquake liquefaction prevention system comprises a pore pressure sensor, an acquisition instrument, an alarm and a water pump; the pore pressure sensor consists of a pore pressure sensor probe (6), sensor leads and a channel thereof, wherein the pore pressure sensor probe (6) is uniformly distributed in the reverse filtration water guide hole (2-1) on the surface of the hollow concrete pile foundation (2) in a criss-cross manner and is connected with the sensor leads, and the sensor leads are connected with a sensor interface panel (1-3) through the channel thereof; the sensor interface panel (1-3) is connected with an acquisition instrument through a lead, the acquisition instrument, an alarm and a water pump are sequentially connected, the drainage pipe interface (1-2) is communicated with the drainage pipe main body (3-2), the drainage function of the automatic earthquake liquefaction prevention and control system can be realized, the acquisition instrument reads the measured pore water pressure, when the data measured by the acquisition instrument obviously rises compared with the original pore pressure of the same soil layer, the alarm gives an alarm and utilizes the water pump to drain water, and the automatic earthquake liquefaction prevention and primary control are realized; the alarm stores the displacement early warning value of the actual engineering side slope, and when the side slope is too large in deformation or too fast in deformation speed and exceeds the early warning value, the alarm gives an alarm and utilizes the pressure grouting device to perform grouting in the pile foundation, so that the depth control of the earthquake liquefaction of the engineering soil side slope is realized.
2. The pile foundation for the prevention and the treatment of the earthquake liquefaction landslide of the engineering soil slope according to claim 1, characterized in that: the pile foundation is applied to the prevention and treatment of gradual fluidity engineering soil slope landslide and gradual plasticity engineering soil slope landslide; soil body damage characteristics of the gradual fluidity engineering soil slope landslide and the gradual plasticity engineering soil slope landslide are obtained by performing a dynamic triaxial test of seismic liquefaction on a sample with consistency and porosity ratio consistent with those of a filling slope; the following four figures are sequentially arranged according to the test data: (a) axial strain-cycle number plot; (b) hyperstatic pore water pressure-cycle number diagram; (c) offset stress-axial strain diagram; (d) offset stress — mean effective stress map;
the soil body destruction of the gradual fluidity engineering soil slope landslide is generated after the soil body strength is softened under the earthquake cycle dynamic load, and is characterized in that:
according to the axial strain-cycle number diagram, the axial strain does not vibrate up and down obviously in the initial several cycles of the action of the cyclic dynamic load; after the periodic action of a plurality of circulating power loads, the axial strain of the sample vibrates up and down along with the circulating times of the power loads, and the vibration amplitude is continuously increased until the soil body of the sample is subjected to circulating liquefaction damage;
according to the hyperstatic pore water pressure-cycle times diagram, the hyperstatic pore pressure is vibrated and increased under the action of a cyclic power load, and when the maximum value of the hyperstatic pore water pressure reaches or approaches to an effective confining pressure value, the soil body is subjected to cyclic liquefaction damage; in a plurality of cycle periods before the soil body is subjected to cyclic liquefaction damage, the amplitude of the hyperstatic pore water pressure oscillation is subjected to mutation;
according to an offset stress-axial strain diagram, at the initial stage of the action of the cyclic dynamic load, the axial strain is basically kept unchanged, and the offset stress oscillates up and down; after the periodic action of a plurality of cyclic power loads, the axial strain of the sample vibrates along with the vertical vibrating bias stress until the soil body of the sample is subjected to cyclic liquefaction damage;
according to the bias stress-average effective stress diagram, under the action of cyclic power load, the average effective stress is continuously reduced along with the bias stress oscillating up and down; when the oscillation minimum value of the average effective stress reaches or is even smaller than a zero value, the soil body is subjected to cyclic liquefaction damage;
the soil body destruction characteristic of the progressive plastic engineering soil slope landslide is that under the action of earthquake cycle power load, soil body plastic deformation is accumulated until deformation is overlarge, but obvious destruction does not occur, and the soil body destruction characteristic is as follows:
according to an axial strain-cycle number diagram, under the action of a cycle power load, the axial strain of the sample is vibrated and increased along with the cycle number of the power load until the axial strain of the sample is too large and the soil body is subjected to plastic damage;
according to the hyperstatic pore water pressure-cycle times diagram, under the action of cyclic power load, the hyperstatic pore water pressure shock is increased, the amplitude of the hyperstatic pore water pressure shock is also increased, and the shock maximum value of the hyperstatic pore water pressure is close to the effective confining pressure value continuously until the axial strain of the sample is overlarge and the soil body is subjected to plastic damage;
according to the offset stress-axial strain diagram, under the action of cyclic power load, the axial strain of the sample is continuously increased along with the offset stress of up-down oscillation until the axial strain of the sample is overlarge and can not be recovered, and the soil body is subjected to plastic damage;
according to the bias stress-average effective stress diagram, under the action of cyclic power load, the average effective stress is continuously reduced along with the bias stress oscillating up and down; the maximum value of the average effective stress has no obvious vibration reduction amplitude change, but the minimum value of the average effective stress has a remarkable vibration reduction trend; when the oscillation minimum value of the average effective stress reaches or is even smaller than a zero value, the axial strain of the sample is overlarge, and the soil body is subjected to plastic damage.
3. The pile foundation for the prevention and the treatment of the earthquake liquefaction landslide of the engineering soil slope according to claim 1, characterized in that: the drainage pipe interface (1-2) and the sensor interface panel (1-3) adopt a mechanical sealing interface technology to ensure that the drainage pipe interface (1-2) and the sensor interface panel (1-3) are completely sealed.
4. The pile foundation for the prevention and the treatment of the earthquake liquefaction landslide of the engineering soil slope according to claim 1, characterized in that: the opening of the reverse filtering water guide pipe (3-1) is provided with a water discharge plate (3-1-2), the surface of the reverse filtering water guide pipe is provided with a reverse filtering layer (3-1-1), and soil particles are not communicated only when water is supplied, so that the loss of the soil particles in the soil layer during the drainage process of the pile foundation is prevented.
5. The pile foundation for the prevention and the treatment of the earthquake liquefaction landslide of the engineering soil slope according to claim 1, characterized in that: the tail of the one-way grouting pipe (4-2) is provided with a one-way valve (4-2-1), and the one-way valve (4-2-1) ensures that only the slurry can flow out but not flow in, namely, the slurry can enter a seepage failure area through the one-way valve (4-2-1) for reinforcement, and seepage water backflow caused by soil layer particle loss or liquefaction can be prevented.
6. The pile foundation for the prevention and the treatment of the earthquake liquefaction landslide of the engineering soil slope according to claim 1, characterized in that: the electromagnet grouting end (5-2) is attracted to the iron limiting end (5-3) after being electrified, the grouting pipe main body (5-1) and the two ends are pulled, grouting limiting can be achieved, and the grouting pipe main body (5-1) is pulled after the power is off, so that a sufficient grouting space is reserved between the two ends.
7. The pile foundation for the prevention and the treatment of the earthquake liquefaction landslide of the engineering soil slope according to claim 1, characterized in that: the quantity and the diameter of the reverse filtering water guide holes (2-1) and the one-way grouting holes (2-2) can be properly increased or decreased according to the diameter of the pile foundation in specific engineering, and the specifications of the reverse filtering water guide pipes (3-1) and the one-way grouting pipes (4-2) correspond to the corresponding reserved channel holes.
8. A construction method of a pile foundation for the prevention and treatment of earthquake liquefaction landslide of an engineering soil slope according to claim 1, characterized by comprising the steps of:
(1) carrying out pile position measurement and placement according to a project site plan and coordinate control points, determining a pile position, driving a short steel bar at the center of the pile position, coating red paint, and repeatedly measuring the pile position after positioning;
(2) installing a pore pressure sensor detection group in a prefabricated pile foundation, firstly, enabling a pore pressure sensor probe (6) and a pore pressure test surface to be tangent to the outer side wall of a hollow concrete pile foundation (2), fixedly installing the pore pressure sensor probe in a reverse filtration water guide hole (2-1), and connecting the pore pressure sensor probe (6), a sensor interface panel (1-3), a collecting instrument and an alarm through wires;
(3) the pile foundation is prefabricated by static pressure by a pile pressing machine, and the pile foundation has a certain depth in a stable soil layer to enhance the earthquake liquefaction resistance of the pile foundation;
(4) after the pile foundation is installed, a proper amount of air pressure is added to clean the holes of the one-way grouting pipe (4-2) and the reverse filtration water guide pipe (3-1), so that the reverse filtration layer and the one-way valve are prevented from being blocked by soil particles to influence the working effect of the device; the one-way valve is arranged at the tail part of the one-way grouting pipe (4-2);
(5) reading data measured by a pore pressure sensor probe (6) by using a collector, when the data measured by the collector is obviously increased compared with the original pore pressure of the same soil layer, alarming by using an alarm and draining by using a water pump, allowing water carrying soil particles to enter a reverse filtering water guide hole (2-1) on the surface of the hollow concrete pile foundation, leaving the soil particles on the soil layer through a reverse filtering layer (3-1-1) and a drainage plate (3-1-2), and simultaneously discharging the water subjected to reverse filtering out of a rock-soil layer through a drainage pipe (3), thereby realizing the prevention and primary treatment of the earthquake liquefaction of the engineering soil slope;
(6) monitoring the slope displacement by adopting a conventional displacement monitoring method, calculating to obtain an actual engineering slope displacement early warning value according to relevant specifications, inputting the early warning value into an alarm, and when the slope deformation is too large or the deformation speed is too high and exceeds the early warning value, alarming by the alarm and entering a grouting step;
(7) opening a sealing plug (1-4) on a pile cap (1), electrifying an electromagnet grouting end (5-2), sucking an iron limiting end (5-3), pulling a grouting pipe (5) to enable a grouting pipe main body (5-1) to drive two ends to reach positions needing grouting, powering off, pulling the grouting pipe (5) to enable the two ends to be separated, ensuring that enough grouting space exists between the two ends, grouting into a pile foundation by using a pressure grouting device, cleaning holes before final setting after grout is initially set, preventing grout from blocking a pipe orifice, and realizing deep treatment of engineering soil slope earthquake liquefaction.
9. The construction method according to claim 8, wherein: in the step (2), considering the construction cost, pore pressure sensor probes (6) are uniformly distributed in the part of the reverse filtration water guide holes (2-1) on the surface of the hollow concrete pile foundation (2) in a criss-cross mode.
10. The construction method according to claim 8, wherein: and (3) vertically inserting and beating the prefabricated pile foundation by static force, so that the phenomenon that the original mechanical property of the soil body is changed by power inserting and beating to cause artificial soil layer liquefaction is avoided.
CN202010885376.0A 2020-08-28 2020-08-28 Pile foundation for preventing and treating earthquake liquefaction landslide of engineering soil slope and construction method thereof Active CN112064624B (en)

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