CN105200971B - Device and method for testing pile-soil interface soil and pore water pressure - Google Patents

Abstract

The invention belongs to the technical field of building construction equipment, and relates to a pile-soil interface soil and pore water pressure test device and method. Silicon piezoresistive pressure sensors are embedded and symmetrically installed at different sections and pile ends on the outer wall of high-strength prestressed concrete pipe piles. Earth pressure gauge and silicon piezoresistive pore water pressure gauge, the top inside of the high-strength prestressed concrete pipe pile is drilled in the pile body, and the armored optical cable is connected with the YE2539 high-speed static strain gauge through the pile body borehole; the high-strength prestressed concrete pipe pile The pile end of the pile is covered with a steel plate, and the silicon piezoresistive soil pressure gauge and the silicon piezoresistive pore water pressure gauge at the bottom are installed on the bottom of the steel plate with the measuring head facing down. Groove; its structure is simple and compact, small in size, light in weight, low in cost, easy to operate, strong and durable, has excellent dynamic and static characteristics, wide range, high measurement accuracy, high sensitivity, and is easy to realize the pile-soil interface close to the pile body Earth pressure and pore water pressure tests.

Description

Device and method for testing pile-soil interface soil and pore water pressure

Technical field:

The invention belongs to the technical field of building construction equipment, and relates to a prefabricated pile pile-soil interface soil pressure and pile-soil interface pore water pressure test device for foundation and foundation engineering constructed by static pressure method, in particular to a static pressure high-strength prestressed concrete The invention relates to a device and a method for testing the pressure of the pile-soil interface soil and pore water adjacent to the pile body of the pipe pile.

Background technique:

In cities, traditional hammer piles and other dynamic piles produce environmental problems such as noise and vibration, while static pressure piles have been more and more widely used due to their relatively small impact on the environment. For the measurement of the static pressure pile sinking process and the rest period after the pile sinking, the earth pressure and pore water pressure are measured. The traditional method is to embed an earth pressure gauge and a pore water pressure gauge in the affected soil layer at a certain distance around the pile, and test the pipe pile. The change of soil pressure and pore water pressure in the soil at a certain distance around the pile during the pile sinking process, but the mechanical characteristics of the pile-soil interface from the pile sinking, not only reflects the pile sinking resistance (pile pressing force) at the penetration stage, It also reflects the bearing capacity that changes with time. The soil pressure and pore water pressure at the pile-soil interface close to the pile body directly act on the pile body, which is more important than that far away from the pile body. Due to the limited test conditions and research level, the current research on the pile-soil interface is not deep enough, especially the accurate measurement of the soil pressure and pore water pressure at the pile-soil interface adjacent to the pile body. Because the survival rate of the traditional earth pressure gauge and pore water pressure gauge is not high at the pile-soil interface, it is not suitable for the test of the pile-soil interface soil pressure and pore water pressure. Therefore, a pile-soil interface soil and pore water pressure test device is designed. and method, it is the first time to use silicon piezoresistive sensor to test earth pressure and pore water pressure. This kind of sensor uses micro-processed silicon diaphragm as the core component, high-precision integrated piezoresistive sensitive element, and uses international advanced miniaturization manufacturing and packaging technology. , with exquisite and ingenious micro-encapsulation, the product is small in size, compact in structure, light in weight, strong and durable, has excellent dynamic and static characteristics, and has a wide range of measurements. This kind of testing device and method has not been reported in the literature.

Invention content:

The purpose of the present invention is to overcome the shortcoming that prior art exists, seek to design through a kind of soil and pore water pressure testing device and method at the pile-soil interface place close to the pile body, according to the soil layer interface, in pile body different section and pile A silicon piezoresistive soil pressure gauge was installed symmetrically at the end to test the lateral soil pressure at the pile-soil interface, and a silicon piezoresistive pore water pressure gauge was installed symmetrically at the test section at the same time to test the pore water pressure at the pile-soil interface.

In order to achieve the above object, the main structure of the present invention includes high-strength prestressed concrete pipe pile, silicon piezoresistive earth pressure gauge, silicon piezoresistive pore water pressure gauge, armored optical cable, pile body drilling, YE2539 high-speed static strain gauge and steel plate; according to the interface of different soil layers, silicon piezoresistive earth pressure gauges and silicon piezoresistive soil pressure gauges are embedded and symmetrically installed on the outer wall of the high-strength prestressed concrete pipe pile formed by the static pressure method and at the bottom of the pile. For pore water pressure gauges, the adjacent silicon piezoresistive earth pressure gauges and the adjacent silicon piezoresistive pore water pressure gauges are connected by armored optical cables, and filled with epoxy resin for encapsulation; adjacent silicon piezoresistive pressure gauges The distance between the earth pressure gauges and the adjacent silicon piezoresistive pore water pressure gauges decreases sequentially from the pile end to the bottom of the pile, forming a dense structure at the top; the top of the high-strength prestressed concrete pipe pile has a pile body The armored optical cable is connected to the YE2539 high-speed static strain gauge through the borehole of the pile body; the pile bottom of the high-strength prestressed concrete pipe pile is covered with a steel plate with a thickness of 20mm, and the silicon piezoresistive earth pressure gauge and silicon piezoresistive pressure gauge at the bottom end The type pore water pressure gauge is installed on the bottom of the steel plate with the measuring head facing down. There are holes on the steel plate to match the armored optical cable, so that the armored optical cable can be installed.

The silicon piezoresistive soil pressure gauge and the silicon piezoresistive pore water pressure gauge of the present invention both adopt silicon piezoresistive pressure sensors, and the self-packaging form is that the silicon strain gauge is directly sintered with glass powder on the metal diaphragm to form a sintered type. Pressure sensor, silicon piezoresistive pressure sensor has a minimum diameter of 4mm and a minimum height of 10mm. The silicon piezoresistive pressure sensor can make the elastic element directly contact with the measured medium, which is easy to miniaturize and is suitable for dynamic force measurement.

The concrete process that the present invention tests the soil and pore water pressure at the pile-soil interface is:

(1) First, grooves are carved on high-strength prestressed concrete pipe piles, and silicon piezoresistive soil pressure gauges and silicon piezoresistive pore water pressure gauges are symmetrically implanted in different sections and pile bottoms according to the interface of different soil layers. At the same time, silicon piezoresistive temperature compensation gauges are installed at the positions of each cross-section pressure gauge to eliminate the earth pressure and pore water pressure caused by temperature. The pipe piles are densely installed at the bottom of the pile, the measuring head of the silicon piezoresistive soil pressure gauge and the silicon piezoresistive pore water pressure gauge are flush with the pile surface, and the silicon piezoresistive soil pressure gauge and silicon piezoresistive pressure gauge are preliminarily fixed Carefully pour epoxy resin into the position of the type pore water pressure gauge, and adjust the leveling again before the epoxy resin solidifies;

(2), seal the bottom of the high-strength prestressed concrete pipe pile with a steel plate with a thickness of 20 mm, and install a silicon piezoresistive soil pressure gauge and a silicon piezoresistive pore water pressure gauge at the bottom of the steel plate to make the silicon piezoresistive soil pressure The measuring head of the gauge and silicon piezoresistive pore water pressure gauge faces downward, and a hole groove is reserved on the steel plate for installation with the armored optical cable;

(3) Wire the silicon piezoresistive earth pressure gauge and the silicon piezoresistive pore water pressure gauge respectively through the groove, and connect the YE2539 high-speed static strain gauge through the pile body through the armored optical cable. The sampling time is 1s, which fully meets the test requirements of this project; when the high-strength prestressed concrete pipe pile is pressed in, the reading is recorded every 50cm according to the marking line of the high-strength prestressed concrete pipe pile body, and the reading of the earth pressure gauge and the pore water pressure are recorded each time meter reading;

(4) Use the holding pressure static pile driver to penetrate the high-strength prestressed concrete pipe pile at 2 to 3 cm/s, and release the clamp after pressing 2m each time to go up and hold the pile again. In this way, a stroke is completed, and the high-strength prestressed concrete Each stroke of the stress concrete pipe pile is a process of unloading and reloading. During the penetration process, the current voltage value VDC _current of the silicon piezoresistive earth pressure gauge and the silicon piezoresistive pore water pressure gauge are respectively recorded, using the formula _Pcurrent = _Pfull / _Vfull × _VDCcurrent , respectively calculate the lateral earth pressure and pore water pressure of the high-strength prestressed concrete pipe pile, where Pcurrent is the measured _current lateral earth pressure and pore water pressure, unit is kPa; P _full is the full-scale pressure value of the silicon piezoresistive earth pressure gauge and silicon piezoresistive pore water pressure gauge, in kPa; V _full is the silicon piezoresistive earth pressure gauge and silicon piezoresistive pore water pressure The full-scale voltage value of the meter; VDC _current is the measured current voltage value.

Compared with the prior art, the present invention has simple and compact structure, small volume, light weight, low cost, convenient operation, strong and durable, excellent dynamic and static characteristics, wide range, high measurement accuracy, high sensitivity, and easy to realize close proximity The test of soil pressure and pore water pressure at the pile-soil interface of the pile body.

Description of drawings:

Fig. 1 is a schematic diagram of the principle of the main structure of the present invention.

Fig. 2 is a schematic diagram of the principle of the top view of the silicon piezoresistive earth pressure gauge and pore water pressure gauge test pile involved in the present invention.

detailed description:

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

Example:

The main structure of this embodiment includes high-strength prestressed concrete pipe pile 1, silicon piezoresistive earth pressure gauge 2, silicon piezoresistive pore water pressure gauge 3, armored optical cable 4, pile body drilling 5, and YE2539 high-speed static strain gauge 6 and steel plate 7; according to the interfaces of different soil layers, silicon piezoresistive earth pressure gauges 2 and 2 are embedded symmetrically at different sections and pile bottoms on the outer wall of high-strength prestressed concrete pipe pile 1 constructed by static pressure method. Silicon piezoresistive pore water pressure gauges 3, adjacent silicon piezoresistive earth pressure gauges 2 and adjacent silicon piezoresistive pore water pressure gauges 3 are connected by armored optical cables 4, and filled with epoxy resin Encapsulation; the distance between adjacent silicon piezoresistive earth pressure gauges 2 and between adjacent silicon piezoresistive pore water pressure gauges 3 decreases sequentially from the pile end to the pile bottom, forming a sparse upper and denser structure; high-strength prestress The inner side of the top of the concrete pipe pile 1 has a pile body borehole 5, and the armored optical cable 4 is connected with the YE2539 high-speed static strain gauge 6 through the pile body borehole 5; the pile bottom of the high-strength prestressed concrete pipe pile 1 adopts a steel plate with a thickness of 20 mm 7 Back cover, the silicon piezoresistive earth pressure gauge 2 and the silicon piezoresistive pore water pressure gauge 3 at the bottom are installed on the bottom of the steel plate 7 with the measuring head facing down, and the steel plate 7 has a hole for matching with the armored optical cable 4 Groove, so that armored optical cable 4 is installed.

Both the silicon piezoresistive earth pressure gauge 2 and the silicon piezoresistive pore water pressure gauge 3 described in this embodiment use silicon piezoresistive pressure sensors, and the self-packaging form is that the silicon strain gauge is directly sintered on the metal diaphragm with glass frit It constitutes a sintered pressure sensor. The minimum diameter of the silicon piezoresistive pressure sensor is 4mm, and the minimum height is 10mm. The silicon piezoresistive pressure sensor can make the elastic element directly contact with the measured medium, which is easy to miniaturize and is suitable for dynamic force measurement. .

In this embodiment, the specific process of testing the soil and pore water pressure at the pile-soil interface is as follows:

(1) First, grooves are carved on the high-strength prestressed concrete pipe pile 1, and silicon piezoresistive soil pressure gauges 2 and silicon piezoresistive pore water pressure gauges are symmetrically implanted in different sections and pile bottoms according to the interface of different soil layers. Gauge 3, and install silicon piezoresistive temperature compensation gauges at the positions of each cross-section pressure gauge to eliminate the earth pressure and pore water pressure caused by temperature, silicon piezoresistive soil pressure gauge 2 and silicon piezoresistive pore water pressure gauge 3 The high-strength prestressed concrete pipe pile 1 is densely installed at the bottom of the pile. The silicon piezoresistive earth pressure gauge 2 and the silicon piezoresistive pore water pressure gauge 3 are flush with the pile surface, and the silicon piezoresistive is initially fixed with a steel wire formwork. The positions of the type earth pressure gauge 2 and the silicon piezoresistive pore water pressure gauge 3 are then carefully poured into the epoxy resin package, and the leveling is adjusted again before the epoxy resin solidifies;

(2), the pile bottom of the high-strength prestressed concrete pipe pile 1 is sealed with a steel plate 7 with a thickness of 20mm, and a silicon piezoresistive earth pressure gauge 2 and a silicon piezoresistive pore water pressure gauge 3 are installed on the bottom of the steel plate to make the silicon pressure The probes of the resistive earth pressure gauge 2 and the silicon piezoresistive pore water pressure gauge 3 face downward, and a hole groove for matching with the armored optical cable 4 is reserved on the steel plate 7;

(3) Wire the silicon piezoresistive earth pressure gauge 2 and the silicon piezoresistive pore water pressure gauge 3 respectively through the grooves, and connect the YE2539 high-speed static strain gauge 6 through the armored optical cable 4 through the borehole 5 of the pile body , the minimum sampling time of all measuring points is 1s, which fully meets the test requirements of this project; when the high-strength prestressed concrete pipe pile 1 is pressed in, the reading is recorded every 50cm according to the marking line of the high-strength prestressed concrete pipe pile 1, and the soil is recorded every time Pressure gauge readings and pore water pressure gauge readings;

(4) Use the holding pressure static pile driver to penetrate the high-strength prestressed concrete pipe pile 1 at a rate of 2 to 3 cm/s, and release the clamp after pressing 2m each time to go up and hold the pile again. In this way, a stroke is completed, and the high-strength Each stroke of the prestressed concrete pipe pile 1 is a process of unloading and reloading. During the penetration process, the current voltage value VDC of the silicon piezoresistive earth pressure gauge 2 and the silicon piezoresistive pore water pressure gauge 3 are respectively recorded _Currently , use the formula _Pcurrent = _Pfull / _Vfull × _VDCcurrent to calculate the lateral earth pressure and pore water pressure of the high-strength prestressed concrete pipe pile 1 respectively, where Pcurrent is the measured _current lateral earth pressure and pore water pressure Water pressure value, unit is kPa; P _full is the full-scale pressure value of silicon piezoresistive earth pressure gauge 2 and silicon piezoresistive pore water pressure gauge 3, unit is kPa; V _full is silicon piezoresistive earth pressure gauge 2 and the full-scale voltage value of the silicon piezoresistive pore water pressure gauge 3; VDC _{is currently} the measured current voltage value.

Claims (3)

1. at a kind of Soil Interface soil and pore water pressure method of testing it is characterised in that stake Soil Interface soil and pore water pressure Realize in force test device, its detailed process is:

(1), first cutting on high-strength prestressed concrete pipe pile, according to the separating surface of different soil, at different cross section and stake bottom Symmetrical implantation silicon piezoresistance type earth pressure gauge and silicon piezoresistance type pore pressure gauge, install silicon in the position of each sectional pressure meter simultaneously Voltage-resistor type temp compensates meter, excludes the soil pressure because temperature produces and pore water pressure, silicon piezoresistance type earth pressure gauge and silicon pressure drag Formula pore pressure gauge is in the intensive installation in high-strength prestressed concrete pipe pile stake bottom, silicon piezoresistance type earth pressure gauge and silicon piezoresistance type The gauge head of pore pressure gauge is flushed with stake surface, with the tentatively fixing silicon piezoresistance type earth pressure gauge of steel wire mould bases and silicon piezoresistance type hole Carefully pour into epoxy encapsulation again behind the position of gap WG, and adjust levelling before epoxy resin solidification again；

(2), the stake bottom of high-strength prestressed concrete pipe pile is used the steel plate back cover of thick 20mm, and in steel plate bottom, silicon pressure drag is installed Formula earth pressure gauge and silicon piezoresistance type pore pressure gauge, make silicon piezoresistance type earth pressure gauge and the survey of silicon piezoresistance type pore pressure gauge Upside down, the hole slot installed with armored optical cable cooperation is reserved on steel plate；

(3), silicon piezoresistance type earth pressure gauge and silicon piezoresistance type pore pressure gauge are passed through cutting cabling respectively, by armored optical cable Through pile body hole access ye2539 high speed static deformeter, high-strength prestressed concrete pipe pile press-in when, according to high-strength pre- should Power concrete tubular pile pile body rules every 50cm read-record once, and record earth pressure gauge reading and pore pressure gauge are read every time Number；

(4), hugging pressure type static pile press is adopted high-strength prestressed concrete pipe pile to be pressed 2～3cm/s injection, after being pressed onto 2m every time Unclamp the up pressure of embracing again of fixture and complete a stroke, penetration process records silicon piezoresistance type earth pressure gauge and silicon pressure drag respectively The current voltage value vdc of formula pore pressure gauge_Currently, using formula p_Currently=p_Full/v_Full×vdc_Currently, calculate high-strength prestressed respectively The soil lateral pressure of concrete tubular pile and pore water pressure, wherein, p_CurrentlyFor the current soil lateral pressure that records and pore water pressure Value, unit is kpa；p_FullFor the full-scale pressure value of silicon piezoresistance type earth pressure gauge and silicon piezoresistance type pore pressure gauge, unit is kpa；v_FullFull range voltage value for silicon piezoresistance type earth pressure gauge and silicon piezoresistance type pore pressure gauge；vdc_CurrentlyFor working as of recording Front magnitude of voltage.

2. according to claim 1 at stake Soil Interface soil and pore water pressure method of testing it is characterised in that described stake is native The agent structure of interface soil and pore water pressure force test device includes high-strength prestressed concrete pipe pile, silicon piezoresistance type soil pressure Meter, the boring of silicon piezoresistance type pore pressure gauge, armored optical cable, pile body, ye2539 high speed static deformeter and steel plate；According to difference The separating surface of soil layer, on the high-strength prestressed concrete pipe pile lateral wall being formed with static pressure construction, different cross section and stake bottom are divided Not embedded it is symmetrically installed with silicon piezoresistance type earth pressure gauge and silicon piezoresistance type pore pressure gauge, adjacent silicon piezoresistance type earth pressure gauge Between all connected by armored optical cable and adjacent silicon piezoresistance type pore pressure gauge between, and pour into epoxy encapsulation；Adjacent It is sequentially reduced to stake bottom from stake end with the distance between adjacent silicon piezoresistance type pore pressure gauge between silicon piezoresistance type earth pressure gauge, Close structure under dredging in formation；The inside top of high-strength prestressed concrete pipe pile has pile body boring, and armored optical cable passes through pile body Boring is connected with ye2539 high speed static deformeter；The stake bottom of high-strength prestressed concrete pipe pile adopts the steel plate that thickness is 20mm Back cover, the silicon piezoresistance type earth pressure gauge of lowermost end and silicon piezoresistance type pore pressure gauge are arranged on the bottom of steel plate, and gauge head court Under, steel plate has the hole slot with armored optical cable cooperation, to install armored optical cable.

3. according to claim 2 at stake Soil Interface the method for testing of soil and pore water pressure it is characterised in that described silicon pressure , all using silicon piezoresistance type pressure sensor, itself packing forms is by silicon for resistive earth pressure gauge and silicon piezoresistance type pore pressure gauge Foil gauge glass dust direct sintering constitutes slug type pressure transducer on metallic membrane, and silicon piezoresistance type pressure sensor is Minor diameter is 4mm, and minimum constructive height is 10mm.