CA1070517A - Method and device for determining the pore water pressure in a soil - Google Patents
Method and device for determining the pore water pressure in a soilInfo
- Publication number
- CA1070517A CA1070517A CA253,590A CA253590A CA1070517A CA 1070517 A CA1070517 A CA 1070517A CA 253590 A CA253590 A CA 253590A CA 1070517 A CA1070517 A CA 1070517A
- Authority
- CA
- Canada
- Prior art keywords
- pore
- measuring device
- pore pressure
- pressure
- probe
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000011148 porous material Substances 0.000 title claims abstract description 65
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 37
- 238000000034 method Methods 0.000 title claims abstract description 13
- 239000002689 soil Substances 0.000 title claims abstract description 11
- 239000000523 sample Substances 0.000 claims abstract description 41
- 239000004927 clay Substances 0.000 claims abstract description 4
- 210000002445 nipple Anatomy 0.000 claims description 9
- 239000004677 Nylon Substances 0.000 claims description 2
- 229920001778 nylon Polymers 0.000 claims description 2
- 229910010293 ceramic material Inorganic materials 0.000 claims 1
- 229910001220 stainless steel Inorganic materials 0.000 claims 1
- 239000010935 stainless steel Substances 0.000 claims 1
- 238000005259 measurement Methods 0.000 description 5
- 238000009530 blood pressure measurement Methods 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
- E21B47/06—Measuring temperature or pressure
-
- 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
- E02D1/02—Investigation of foundation soil in situ before construction work
- E02D1/027—Investigation of foundation soil in situ before construction work by investigating properties relating to fluids in the soil, e.g. pore-water pressure, permeability
Abstract
METHOD AND DEVICE FOR DETERMINING
THE PORE WATER PRESSURE IN A SOIL
Abstract of the Disclosure A method and apparatus for determining the pore water pressure in a soil, especially clay, in which the pore pressure probe can be lowered into position separately of the pressure measuring device. A water-filled tube bearing the pore pressure probe at its lower end is installed at the required level, the probe having a filter through which pressure can be measured, and the measuring device is subsequently lowered into the tube and connected to the pore pressure probe. A reading is taken when the pressure has stabilized, and the measuring device is then disconnected from the pore water probe and the water pressure within the tube is noted, the pore pressure being then calculated from the two pressure readings. The separate pressure measuring device allows the operative parts of apparatus to be less expensive than known tips.
THE PORE WATER PRESSURE IN A SOIL
Abstract of the Disclosure A method and apparatus for determining the pore water pressure in a soil, especially clay, in which the pore pressure probe can be lowered into position separately of the pressure measuring device. A water-filled tube bearing the pore pressure probe at its lower end is installed at the required level, the probe having a filter through which pressure can be measured, and the measuring device is subsequently lowered into the tube and connected to the pore pressure probe. A reading is taken when the pressure has stabilized, and the measuring device is then disconnected from the pore water probe and the water pressure within the tube is noted, the pore pressure being then calculated from the two pressure readings. The separate pressure measuring device allows the operative parts of apparatus to be less expensive than known tips.
Description
This invention concerns a method and equipment for determining the pore water pressure in a soil, especially clay.
At present there are a large number of methods of determining pore water pressure. A distinction is made between "closed" and "open" measuring systems. In a closed measuring system only a relatively small change in volume is needed for ~he registration of the pressure, whereas in an open system a large change in volume is necessary. This invention is primarily intended for the measurement of the pore water pressure in clays, and consists of a closed measuring system.
The biggest disadvantage of the closed measuring systems available today is that the measuring unit is fitted to the pressure sounding tip. This means that the tips are expensive and that it is difficult to make a functional check of the pressure sensing element.
The purpose of the invention in question is to offer a method in which the above disadvantages can be avoided. This is done using the following procedure for determining the pore water pressure in a soil:
1. A water-filled tube bearing a pore pressure probe at its lower end is installed at the required level. The pore pressure probe bears a filter through which the pore pressure in the soil is conveyed.
At present there are a large number of methods of determining pore water pressure. A distinction is made between "closed" and "open" measuring systems. In a closed measuring system only a relatively small change in volume is needed for ~he registration of the pressure, whereas in an open system a large change in volume is necessary. This invention is primarily intended for the measurement of the pore water pressure in clays, and consists of a closed measuring system.
The biggest disadvantage of the closed measuring systems available today is that the measuring unit is fitted to the pressure sounding tip. This means that the tips are expensive and that it is difficult to make a functional check of the pressure sensing element.
The purpose of the invention in question is to offer a method in which the above disadvantages can be avoided. This is done using the following procedure for determining the pore water pressure in a soil:
1. A water-filled tube bearing a pore pressure probe at its lower end is installed at the required level. The pore pressure probe bears a filter through which the pore pressure in the soil is conveyed.
2. A measuring device is lowered down the tube and fitted on to the pore pressure probe.
3. The pore pressure is then allowed to stabilize after which a reading is taken which represents the pore pressure in the soil.
4. The measuring device is disconnected from the pore pressure probe and a reading is taken which represents the water pressure in the tube.
5. The pore pressure is calculated by comparison of the reading for pore water pressure and the water pressure in the tube, using a calibration factor for the measuring device.
In accordance with another aspect, the invention relates to a device for determination of pore water pressures which comprises a water-filled tube, a pore pressure probe with a filter at the lower end of the tube, a measuring device with a pressure transducer, means for detachably connecting the measuring device to the pore pressure probe from within the water filled tube, and an electric cable which connects the measuring device to a read-out unit.
Below a description will be given of an embodiment of the invention with reference to the attached drawings, wherein:
Fig. 1 shows an embodiment of a device according to the invention;
Fig. 2 shows at a larger scale a cross section through an embodiment of the pore pressure probe; and Fig. 3 shows at the same scale as Fig. 2 a section through an embodiment of the measuring device.
The device shown in Fig. 1 includes a water-filled tube 1 which has been installed in the ground. At the lower ; end of the tube 1 a pore pressure probe 2 has been attached.
An embodiment of a pore pressure probe will be shown in greater - detail in Fig. 2. The device shown ~n Fig. 1 also includes a measuring de~ice 3, which has been lowered down the tube 1, and 3Q fitted tightly on to a nipple on the pore pressure probe 2.
Fig. 3 shows a preferred embodiment of a measuring device at a ~0705~7 larger scale. As shown in Fig. 1, the measuring device 3 is connected to an electronic read-out unit 4 via an electric cable 5.
Fig. 2 shows a pore pressure probe 2 at a larger scale. This is screwed onto the threaded tube 1 at its lower end. The pore pressure probe shown here is very narrow and has a conical form. At the lower end of the probe 2 a filter
In accordance with another aspect, the invention relates to a device for determination of pore water pressures which comprises a water-filled tube, a pore pressure probe with a filter at the lower end of the tube, a measuring device with a pressure transducer, means for detachably connecting the measuring device to the pore pressure probe from within the water filled tube, and an electric cable which connects the measuring device to a read-out unit.
Below a description will be given of an embodiment of the invention with reference to the attached drawings, wherein:
Fig. 1 shows an embodiment of a device according to the invention;
Fig. 2 shows at a larger scale a cross section through an embodiment of the pore pressure probe; and Fig. 3 shows at the same scale as Fig. 2 a section through an embodiment of the measuring device.
The device shown in Fig. 1 includes a water-filled tube 1 which has been installed in the ground. At the lower ; end of the tube 1 a pore pressure probe 2 has been attached.
An embodiment of a pore pressure probe will be shown in greater - detail in Fig. 2. The device shown ~n Fig. 1 also includes a measuring de~ice 3, which has been lowered down the tube 1, and 3Q fitted tightly on to a nipple on the pore pressure probe 2.
Fig. 3 shows a preferred embodiment of a measuring device at a ~0705~7 larger scale. As shown in Fig. 1, the measuring device 3 is connected to an electronic read-out unit 4 via an electric cable 5.
Fig. 2 shows a pore pressure probe 2 at a larger scale. This is screwed onto the threaded tube 1 at its lower end. The pore pressure probe shown here is very narrow and has a conical form. At the lower end of the probe 2 a filter
6 has been a~tached. This filter is connected via a duct 7 to a nipple 8. The measuring device 3 shown in Fig. 3 is lowered onto this nipple. At its lower end, this measuring device has a sleeve 9 which fits onto the nipple 8 when the measuring device 3 is lowered. Above the sleeve 9 in the measuring device 3 there is a pressure transducer 10, which is connected to the read-out unit 4 via an electric cable 5.
Pore pressure measurements with the device described above are taken by installing a water-filled tube 1 with a pore pressure probe 2 to the required level. After the disturbance in the soil caused by the penetration of the probe 2 has dissipated, the measuring device 3 is lowered onto the nipple 8 on the pore pressure probe 2. After a short pause while the pore pressure stabilizes, a reading is taken by the read-out unit 4. This reading applies to the pore pressure at the level of the filter 6. After this, the measuring device 2 is disconnected from the nipple 8. A reading which represents the water pressure in the tube 1 is then taken. As this water pressure is known, due to the fact that the length of the tube 1 is known, the pore pressure can be calculated with the help of the following formula:
u = pO + k ~ml m2) where u = pore water pressure O = water pressure in tube .~-~, '~,~1' k = calibration coefficient for the measurement system ml = reading for pore water pressure m2 = reading for water pressure in tube Qh = distance between pressure transducer and centre of filter.
The readings mentioned above are those supplied by the measuring device 3. These values are then converted by multiplying by the calibration coefficient to give a pressure expressed in a suitable unit, for example in cm water column.
The procedure described above is thus very simple for the people doing the fieldwork. Only two readings are taken: that of the pore water pressure, and that of the water pressure in the tube. For example one is thus not dependent on being able to check possible zero shift of the measurement system.
The equipment is also very simple, and has distinct advantages over equipment previously known. If, for example, the method described above is used for long-time measurements, it is a great advantage that the measuring device is not built into the pore pressure probe, which would make the probes expensive, as well as making it difficult to subject the pressure sensing element to functional testing.
Another factor which can cause interruption in pore pressure measurements, especially in clay, is corrosion of the pore pressure probe 2. To avoid interruptions of this kind, the pore pressure probe can be made of nylon with a sintered ceramic filter.
The invention is naturally not limited to the method or devices described above. For example, the pore pressure probe can have a cylindrical shape with mainly even thickness instead of the shape shown in Fig. 2. This cylindrical type of pore pressure probe is especially suited to long-time measurements. Also, the measuring device 3 can have a different construction without departure from the scope of the invention. The invention can thus be varied freely within the scope of protection according to the following patent claims.
_5_
Pore pressure measurements with the device described above are taken by installing a water-filled tube 1 with a pore pressure probe 2 to the required level. After the disturbance in the soil caused by the penetration of the probe 2 has dissipated, the measuring device 3 is lowered onto the nipple 8 on the pore pressure probe 2. After a short pause while the pore pressure stabilizes, a reading is taken by the read-out unit 4. This reading applies to the pore pressure at the level of the filter 6. After this, the measuring device 2 is disconnected from the nipple 8. A reading which represents the water pressure in the tube 1 is then taken. As this water pressure is known, due to the fact that the length of the tube 1 is known, the pore pressure can be calculated with the help of the following formula:
u = pO + k ~ml m2) where u = pore water pressure O = water pressure in tube .~-~, '~,~1' k = calibration coefficient for the measurement system ml = reading for pore water pressure m2 = reading for water pressure in tube Qh = distance between pressure transducer and centre of filter.
The readings mentioned above are those supplied by the measuring device 3. These values are then converted by multiplying by the calibration coefficient to give a pressure expressed in a suitable unit, for example in cm water column.
The procedure described above is thus very simple for the people doing the fieldwork. Only two readings are taken: that of the pore water pressure, and that of the water pressure in the tube. For example one is thus not dependent on being able to check possible zero shift of the measurement system.
The equipment is also very simple, and has distinct advantages over equipment previously known. If, for example, the method described above is used for long-time measurements, it is a great advantage that the measuring device is not built into the pore pressure probe, which would make the probes expensive, as well as making it difficult to subject the pressure sensing element to functional testing.
Another factor which can cause interruption in pore pressure measurements, especially in clay, is corrosion of the pore pressure probe 2. To avoid interruptions of this kind, the pore pressure probe can be made of nylon with a sintered ceramic filter.
The invention is naturally not limited to the method or devices described above. For example, the pore pressure probe can have a cylindrical shape with mainly even thickness instead of the shape shown in Fig. 2. This cylindrical type of pore pressure probe is especially suited to long-time measurements. Also, the measuring device 3 can have a different construction without departure from the scope of the invention. The invention can thus be varied freely within the scope of protection according to the following patent claims.
_5_
Claims (10)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Method of determining the pore water pressure in a soil, especially clay, characterized by the following steps:
(a) a water-filled tube bearing a pore pressure probe at its lower end is installed at the required level, said pore pressure probe bearing a filter through which the pore pressure in the soil is conveyed;
(b) a measuring device is lowered down the tube and connected to the pore pressure probe;
(c) the pore pressure is then allowed to stabilize, after which a reading is taken which represents the pore pressure in the soil;
(d) the measuring device is disconnected from the pore water probe and a reading is taken which represents the water pressure in the tube;
(e) the pore pressure is calculated by comparison of the readings for the pore water pressure and the water pressure in the tube, using a calibration factor for the measuring device.
(a) a water-filled tube bearing a pore pressure probe at its lower end is installed at the required level, said pore pressure probe bearing a filter through which the pore pressure in the soil is conveyed;
(b) a measuring device is lowered down the tube and connected to the pore pressure probe;
(c) the pore pressure is then allowed to stabilize, after which a reading is taken which represents the pore pressure in the soil;
(d) the measuring device is disconnected from the pore water probe and a reading is taken which represents the water pressure in the tube;
(e) the pore pressure is calculated by comparison of the readings for the pore water pressure and the water pressure in the tube, using a calibration factor for the measuring device.
2. Method according to claim 1, characterized by the fact that the connection of the measuring device to the pore pressure probe is achieved by a sleeve on the measuring device being connected to a nipple on the pore pressure probe.
3. Method according to claims 1 or 2, characterized by readings being taken from an electronic measuring device.
4. A device for determination of pore water pressures which comprises a water-filled tube, a pore pressure probe with a filter at the lower end of the tube, a measuring device with a pressure transducer, means for detachably connecting the measuring device to the pore pressure probe from within the water-filled tube, and an electric cable which connects the measuring device to a read-out unit.
5. A device according to claim 4, characterized by the fact that the means for detachably connecting the measuring device to the pore pressure probe comprises a nipple attached to the pore pressure probe.
6. A device according to claim 5, characterized by the fact that the measuring device includes a sleeve which is connected to the nipple.
7. A device according to claim 4, characterized by the fact that the pore pressure probe narrows conically towards its lower end.
8. A device according to claim 7, characterized by the fact that the pore pressure probe is made of stainless steel.
9. A device according to claim 4, characterized by the fact that the pore pressure probe has a mainly cylindrical form of even thickness.
10. A device according to claim 9, characterized by the fact that the pore pressure probe is made of nylon with a filter of ceramic material.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7506203A SE389923B (en) | 1975-05-30 | 1975-05-30 | PROCEDURE AND DEVICE FOR DETERMINING THE WATER PRESSURE IN A TYPE OF SOIL |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1070517A true CA1070517A (en) | 1980-01-29 |
Family
ID=20324691
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA253,590A Expired CA1070517A (en) | 1975-05-30 | 1976-05-28 | Method and device for determining the pore water pressure in a soil |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5211604A (en) |
| CA (1) | CA1070517A (en) |
| DE (1) | DE2624059A1 (en) |
| FR (1) | FR2312770A1 (en) |
| GB (1) | GB1527048A (en) |
| NL (1) | NL7605670A (en) |
| SE (1) | SE389923B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE411645B (en) * | 1978-05-22 | 1980-01-21 | Torstensson Bengt Arne Harry | DEVICE FOR DETERMINING PORATIC WATER PRESSURE IN AN EARTH |
| JPS5595164A (en) * | 1979-01-12 | 1980-07-19 | Canon Inc | Electronic desk-top calculator on battery drive system |
| JPS56164779U (en) * | 1979-11-21 | 1981-12-07 | ||
| DE3911151A1 (en) * | 1989-04-06 | 1990-10-11 | Joachim Schmidt | Measuring device for determining soil properties |
| DE19501348C2 (en) * | 1995-01-18 | 1996-10-31 | Lausitzer Braunkohle Ag | Method for determining the saturation number of loose rock |
| US6615653B1 (en) * | 2001-09-27 | 2003-09-09 | Geosierra, Llc | In situ method for determining soil liquefaction tendency and its prevention by electro-osmosis |
| CN111721696A (en) * | 2020-05-12 | 2020-09-29 | 温州大学 | Underground soil body effective pressure testing device and testing method |
-
1975
- 1975-05-30 SE SE7506203A patent/SE389923B/en unknown
-
1976
- 1976-05-26 NL NL7605670A patent/NL7605670A/en not_active Application Discontinuation
- 1976-05-28 FR FR7616229A patent/FR2312770A1/en active Granted
- 1976-05-28 CA CA253,590A patent/CA1070517A/en not_active Expired
- 1976-05-28 GB GB22323/76A patent/GB1527048A/en not_active Expired
- 1976-05-28 DE DE19762624059 patent/DE2624059A1/en not_active Withdrawn
- 1976-05-31 JP JP51063454A patent/JPS5211604A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| NL7605670A (en) | 1976-12-02 |
| DE2624059A1 (en) | 1976-12-09 |
| FR2312770A1 (en) | 1976-12-24 |
| FR2312770B3 (en) | 1979-02-16 |
| JPS5211604A (en) | 1977-01-28 |
| JPS544161B2 (en) | 1979-03-03 |
| GB1527048A (en) | 1978-10-04 |
| SE389923B (en) | 1976-11-22 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |