WO2019106635A1

WO2019106635A1 - Improved seismic module

Info

Publication number: WO2019106635A1
Application number: PCT/IB2018/059546
Authority: WO
Inventors: Edoardo PAGANI
Original assignee: Pagani Geotechnical Equipment S.R.L.
Priority date: 2017-12-01
Filing date: 2018-12-01
Publication date: 2019-06-06

Abstract

It is described a seismic module (100) comprising: a tubular body (2) that defines a housing space (2') that comprises a first end (10) that is adapted to be connected to an element piezocone (50), and a second end (20) opposite to the first end (10) that is adapted to be connected to perforation rods (120). A first earthquake sensor (3) is housed within housing space (2'). Is, furthermore, provided a water content sensor (31, 32) housed within housing space (2') and arranged near the first earthquake sensor (3), in order to measuring the water content in the soil around the detection area of the earthquake waves detected by the first earthquake sensor (3).

Description

IMPROVED SEISMIC MODULE

DESCRIPTION

Field of the invention

[001] The present invention relates to an improved seismic module used in the geotechnical field, and more precisely in the holistic investigation of the soil in the earthquakes field.

State of the art

[002] Are known two main technologies to carry out earthquake investigations in a soil. A first technology is known as earthquake detection in probe hole (down- hole - DH), wherein at least one geophone is put down in a preformed hole at a determined depth in order to measure a propagation velocity of the body waves. A second technology is so-called“Seismic Cone Penetrometer” commonly called seismic probe, that consists in a downhole probe that can be used with a penetrometer, commonly a self-propelled type penetrometer.

[003] The down-hole methodology comprises:

an energizing source as for example a mallet that strike on a plate arranged on the soil, in order to generate resilient longitudinal waves (P-wave) and transversal waves (S-wave);

a receiving device adapted to detect a return times of the waves to various depth represented by a geophones system. It is possible to use 3D geophones with only a geophone or two of this suitably spaced,

a registration device of body waves rapresented by a seismograph or by an oscilloscopic.

[004] The only and essential difference between the downhole probe and the probe hole approach is that the downhole probe is arranged and put down at various depths in the soil as a common penetrometer tool.

[005] In particular, the above downhole probe comprises - at a lower end - a conical shaped head which is the function to penetrate into soil pushed by a penetrometer action, and - at an upper end - the downhole probe is screwed to penetrometer tubular rods that can be staked to each other, and by an hydraulic jack, a force that causes advancement steps in the depth of the conical head is provided.

[006] The earthquakes penetrometer analysis allows to measure the longitudinal and transversal waves propagation velocity and, knowing the correlations among these two physical quantities and the natural density of the soils, a parameter of their dynamic response can be provided.

[007] In particular, the earthquake waves as above mentioned can be distinguished in primary waves P and secondary waves S. The detection of these are influenced by a liquid ratio in the soil, in particular a water content. The measurement of the earthquake waves by the above described systems doesn’t keeps in consideration this physic quantity (liquid content) that is commonly detected as additional value carry out by a dedicated investigation.

[008] Such dedicated investigation is however not reliable.

It is therefore felt the need of measuring a water content value in the soil during the same earthquake analysis, and much more in particular, near the detection waves sensor in order to obtain an accurate and instantaneous water content value.

[009] The volumetric water content of the soil thus detected is an important data to carry out an accurate geotechnical analysis and correct interpretation of the measurements.

Summary of the invention

[010] It is therefore an object of the present invention provides an improved seismic module adapted to optimize the analysis of the earthquake waves by a detection of a plurality of values into a same portion of a sampled soil, to obtain a holistic investigation of the soil.

[011] It is another object of the present invention provides an improved seismic module that makes it possible to obtain additional and accurate values concerning the water amount content of the investigate portion of the soil.

[012] It is also an object of the present invention provides an improved seismic module that is structurally easy and not expensive to make.

[013] These and other objects are achieved by an improved seismic module that is adapted to penetrate in the soil comprising:

a tubular body that defines an inner housing space; wherein said tubular body comprises a first end that is adapted to be connected to a piezocone element, and a second end, opposite to the first end, that is adapted to be connected to extension rods,

[014] a first earthquake sensor housed in said housing space in proximity of said first end, wherein a water content sensor is housed in said housing space and arranged in proximity of said first earthquake sensor, said water content sensor is adapted to detect the permittivity or dielectric constant and therefore the amount (ratio) or the volumetric water content of soil in correspondence of the detection area around said earthquake sensor.

[015] In particular, the seismic module is configured as a single element that integrates into a tubular body at least one earthquake sensor, for example an accelerometer, and a water content sensor, for example a dielectric resistance sensor. The water content sensor is arranged close to the earthquake sensor. In this way, it is possible to extract a volumetric water content in the soil in correspondence of the area around said earthquake sensor.

[016] Arranging the water content sensor at far distances from the earthquake sensor, an inexact detection dates are provided. The proximity of the earthquake sensor allows to obtain a volumetric water content value that is an accurate volumetric water content value of the soil layer in which it is substantially arranged the earthquake sensor. Quantifying the volumetric water content and the receiving signal of the earthquake sensor at different depths it is possible to precisely characterizing in a specific area the features of the soil. In particular, it is possible to draft a specific graphic that comprises an average resistance values of the conical head of the probe to the penetration with respect to the volumetric water content on the soil in order to characterize a compaction rate of the soil. Said compaction rate affects the waves propagation velocity.

[017] According to the operation through the piezocone is carried out the penetration in the soil of the whole tubular body, that the more progressively pushed in depth is elongated with further extension rods, connectable in a modular way to investigate at different depth.

[018] Advantageously, is provided a second earthquake sensor housed in said housing space and arranged at said second end of the tubular body, in particular the water content sensor is arranged between said first earthquake sensor and said second earthquake sensor. [019] In this way, a higher precision detection of the earthquake waves is achieved and a plurality of values for a same portion of a sampled soil are obtained.

[020] The receiving signal of each of the two sensors is capable to analyses the behavior of a soil layer defined by the distance between the two earthquake sensors. The water content sensor is arranged in a central portion with respect to the two earthquake sensors, in order to obtain substantially an average volumetric water content value of the soil layer set between the two earthquake sensors.

[021] In particular, said water content sensor is a capacitive sensor that comprises a first electrode and a second electrode that is adapted to measure the resistance and/or permittivity dielectric soil, function of the current detected by said first and second electrode, starting from said resistance value and/or the permittivity dielectric value it is possible to calculate the volumetric water content in the soil by a dedicated transfer function of the detected current.

[022] Advantageously, said tubular body comprises a first portion and a second portion engaged to each other by a connection portion, on said connection portion is arranged said water content sensor. In this way, the tubular body can be divided in more parts to carry out maintenance operations of both earthquake sensors and on the water content sensor.

[023] Preferably a control unit housed in said housing space is provided and that is adapted to receive a resistance signal by said piezocone head to the penetration, at least one earthquake signal coming from said first and/or second earthquake sensor and a dielectric permittivity signal of the soil detected by said water content sensor.

[024] In particular, said control unit comprises program means that is adapted to receive as input said resistance signal of the piezocone head, said at least earthquake signal and said dielectric permittivity signal of the soil in such a way that it is adapted to generate a diagram that correlates an average penetration resistance value of the piezocone head against the penetration with respect to the volumetric water content on the soil, in order to characterizing the compaction rate of the soil, and wherein said program means is adapted to correlating said compaction rate with the propagation velocity of the earthquake waves.

[025] In particular, said control unit is housed in said connection portion. In this way, disengaging the tubular body in the connection portion it is possible to approach the control unit that can be equipped with an interface port in order to setting the operation parameters and/or download the detected dates.

[026] Preferably the first and the second earthquake sensor are arranged opposite to each other in the control unit.

[027] In a preferred exemplary embodiment said first and/or second earthquake sensor are sensors selected from the group consisting of: an accelerometer, a geophone or a combination thereof.

[028] In particular, said tubular body comprises relative apertures or window at said first and second earthquake sensor, in order that a changing or maintenance inspection operations can be provided.

Description of Figs. Of the invention

[029] Further characteristic and advantages of the invention are better shown by the examination of the following detailed description preferred embodiment, but not exclusive, shown for example and not limitative, with the support of the attached drawings, wherein:

- Fig. 1 shows a schematic view of an apparatus for carrying out an earthquake analysis of a soil by a seismic module according to the present invention;

- Fig. 2 shows an elevational front view of an improved seismic module according to the present invention;

- Fig. 3 shows a cross sectional view of the improved seismic module of Fig. 2;

- Figs. 4 and 5 show an elevational front view of the assembled step of the seismic module according to the present invention with a piezocone.

Detailed description of the invention

[030] With reference to Fig. 1 , is shown an improved seismic module 100 according to the present invention.

[031] In particular, the seismic module comprises a tubular body 2 (Fig.3) that defines an inner housing space 2’. The tubular body 2 comprises a first end 10 that is adapted to be connected to an element or piezocone head or simply piezocone 50, and an opposite second end 20 that is adapted to be connected to perforation or extension rods 120 actuated by a perforation machine 200 (Fig.1 ).

[032] Into the tubular housing space 2’ of the body 2, is arranged at least one first earthquake sensor 3, 4. The first earthquake sensor is arranged near the first end 10, i.e. oriented towards the piezocone 50.

[033] The seismic module 100, according to the present invention, comprises, furthermore, a water content sensor 31 , 32 integrated in the outer surface of the tubular body 2. The water content sensor 31 , 32 is adapted to measure the volumetric water content of the soil around the detecting area of the first earthquake sensor 3 and of the piezocone 50.

[034] In particular, the seismic module 100 is configured as a single element monobloc that integrates on the tubular body 2 at least one earthquake sensor 3, for example an accelerometer or geophone, and at least one water content sensor 31 , 32, for example a resistance dielectric sensor. The water content sensor 31 , 32 is arranged in proximity of the earthquake sensor 3, 4 and the piezocone 50. In this way, it is possible to measure a water content in the of the soil at the zone around the receiving zone of the earthquake waves Sw generate through a mallet 150 (Fig.1 ) and also n correspondence of the penetration resistance value detected with the piezocone 50.

[035] In detail, the water content sensor 31 , 32 is arrange at a distance suitable to correlating the receiving signal of the waves to the volumetric water content detected in a predetermined soil layer S1 , S2. IN this way, it is possible to analyze the influence of the liquid content in the soil, in particular water, with respect to the propagation of the waves in the soil.

[036] This particular configuration improves the detection accuracy, and then the following geotechnical analysis for a holistic investigation of the soil.

[037] The proximity to the earthquake sensor 3, 4 allows then to obtain a water content data that relates the predetermined soil layer S1 , S2. Repeating this measurement, in particular with a continuously detection of layers at different depth, it is possible to characterizing the various layers of soil with a respective volumetric water content data associated, a corresponding penetrating resistance value of the piezocone 50, and at least one receiving signal of the earthquake sensor.

[038] In a preferred exemplary embodiment as shown in Fig. 3, a second earthquake sensor 4 housed in said housing space 2’ and arranged at the second end 20 is provided. In particular, the water content sensor 31 , 32 is arranged between the first earthquake sensor 3 and the second earthquake sensor 4. [039] In this way, an accurate detection of earthquake waves and a plurality of dates relating the same sampled portion of soil is obtained.

[040] The signals of the earthquake waves are measured upstream and downstream of the water content sensor so that the dates relative to the earthquake waves can be redundant, for example for a comparation or an interpolation.

[041] In this way, the receiving signals of the two sensors are capable of characterizing the features of a soil layer defined according to the distance D between the two earthquake sensors 3 and 4. The water content sensor 31 , 32 is arranged in a central portion 30 with respect to the two earthquake sensors 3 and 4, in order to obtain substantially an average volumetric water content value of the soil layer set between the two earthquake sensors of the earthquake waves.

[042] In particular, the water content sensor 31 , 32 is a capacitive sensor that comprises a first electrode 31 and a second electrode 32 that is adapted to measure a resistance dielectric or a permittivity dielectric of the soil which is a function of the detected current, from which is therefore possible to determine the volumetric water content in the soil by a dedicated transfer function of the detected current. By the measurement of a side friction of the cone (fs) it is possible to estimating the weight of the volume of a soil, and then transforming the ratio expressed in volume in a ratio expressed by weight a content water is determined.

[043] In other structural aspects, the tubular body 2 comprises, in an alternative exemplary embodiment, a first portion 2a and a second portion 2b fitted to each other by a connection portion 30 (Fig.5). On the connection portion 30 is arranged the water content sensor 31 , 32.

[044] In addition, the seismic module 100 comprises a control unit 40 housed in the housing space 2’ and, in particular, in the central portion 30 of it, that is adapted to receive the signals coming: by the piezocone 50 that measure a resistance signal against the penetration, by the first 3 and/or second 4 earthquake sensor and by the water content sensor 31 , 32. The water content sensor is substantially integrated in the control unit 40, which is made as circuit board with integrated the two electrodes 31 and 32.

[045] The control unit comprises program means that is adapted to receive as input said resistance signal of the piezocone head, said at least earthquake signal and said dielectric permittivity signal of the soil in such a way that it is adapted to generate a diagram that correlates an average resistance value against the penetration with respect to the volumetric water content on the soil, in order to characterizing the compaction rate of the soil, and wherein said program means is adapted to correlating said compaction rate with the propagation velocity of the earthquake waves.

[046] The first 3 and the second earthquake sensor 4 are located opposite to each other in the control unit 40 and connected to this by a respective electric cable 35, 45.

[047] In a preferred exemplary embodiment, the first 3 and/or the second 4 earthquake sensor are sensors selected from the group consisting of: an accelerometer, a geophone or a combination thereof.

[048] Structurally, as shown in Fig. 2, the tubular body 2 comprises relative apertures 3’, 4’ at each respective first 3 and second 4 earthquake sensor. The apertures are hermetically closed with a removable cover. In this way, it is possible to approach the housing space of the two sensors for carrying out for example changing or maintenance operations of the same.

[049] Advantageously, as shown in Fig. 4, the end 10 of the seismic module 100 is conformed to provide a matching fixed joint, to keep a fluid tight connection with the piezocone element 50. The tubular body has seals adapted to ensure a fluid tight resistance of the housing space.

[050] The description of which above at least of one exemplary embodiment is capable of show the invention from a viewpoint conceptual so that other, using the prior art, can be changing and/or adapting in various applications an exemplary embodiments without further researches and without moving away from each other by the concept inventive, and, then is intended that such adaptation and changes will be high as equivalent of an exemplary embodiment specific. The means and the material to provide the various functions described can be changes nature without for this come out from the field of invention. Is intended that the expression or the terminology used have object purely described for this not limitative.

Claims

1. A seismic module (100) comprising:

a tubular body (2) that defines a housing space (2’),

wherein said tubular body (2) comprises a first end (10) that is adapted to be connected to an element piezocone (50), and a second end (20) opposite to the first end (10) that is adapted to be connected to perforation rods (120); a first earthquake sensor (3) housed within said housing space (2’),

characterised in that

a water content sensor (31 , 32) housed within said housing space (2’) is provided, said water content sensor (31 , 32) being arranged near said first earthquake sensor (3), said water content sensor (31 , 32) that is adapted to measure the permittivity dielectric of the soil around a detection area of the earthquake waves detected by said first earthquake sensor (3).

2. Seismic module (100) according to claim 1 , wherein a second earthquake sensor (4) housed within said housing space (2’) is provided.

3. Seismic module (100) according to claim 2, wherein said water content sensor (31 , 32) is arranged between said first earthquake sensor (3) and said second earthquake sensor (4).

4. Seismic module (100) according to claim 1 , wherein said water content sensor (31 , 32) comprises a first electrode (31 ) and a second electrode (32) that is adapted to measure the permittivity dielectric of the soil which is function of the current detected by said first (31 ) and second (32) electrode, and by the permittivity dielectric the water content in the soil by a dedicated transfer function of the detected current.

5. Seismic module (100) according to claim 1 , wherein a control unit (40) housed within said housing space (2’) is provided said control unit (40) being adapted to receive:

a resistance signal against the penetration of said piezocone element (50), at least one earthquake signal (35, 45) coming from said first (3) and/or second (4) earthquake sensor and a dielectric permittivity signal of the soil by said water content sensor (31 , 32).

6. Seismic module (100) according to claim 1 , wherein said control unit (40) comprises program means adapted to generate a graphic curve that correlate a average resistance value of said piezocone (50) to the penetration with respect to the volumetric water content on the soil obtained by said dielectric permittivity signal, in order to characterizing the compaction rate of the soil.

7. Seismic module (100) according to claim 6, wherein said program means is adapted to correlating said compaction rate of the soil with the propagation velocity of the earthquake waves.

8. Seismic module (100) according to claim 1 , wherein said tubular body (2) comprises a first portion (2a) and a second portion (2b) fitted to each other by a connection portion (30), on said connection portion (30) said water content sensor (31 , 32) is arranged.

9. Seismic module (100) according to claim 7, wherein said control unit (40) is housed within said connection portion (30).

10. Seismic module (100) according to claim 1 , wherein said first (3) and/or second earthquake sensor (4) are sensors selected from the group consisting of: an accelerometer, a geophone, or a combination thereof.

11. Seismic module (100) according to claim 1 , wherein said tubular body 2 comprises relative apertures (3’, 4’) at said first (3) and second (4) earthquake sensor, in order that inspection of the two sensors for changing or maintenance operations can be provided.