A method for testing in situ by combining a side pressure test and a flat dilatometer test

Abstract

The present application relates to a kind of in-situ combined test method of lateral pressure test and flat dilatometer test, belong to geotechnical engineering testing field.In the same borehole, lateral pressure test position is set, and one flat dilatometer test position is respectively arranged in the upper and lower direction of the distance lateral pressure test position;Along the borehole depth direction, first flat dilatometer test, lateral pressure test and second flat dilatometer test are sequentially carried out, the change law of lateral pressure test result and the average value of two flat dilatometer test results with test depth is compared, if the similarity of result is greater than preset value, then it indicates that test result is accurate.The present application can objectively reflect the lateral pressure test and flat dilatometer test result of different depth of borehole by the mutual verification of lateral pressure test and flat dilatometer test.Through the comparative analysis of two kinds of test results, more accurate geotechnical parameters can be obtained.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering testing technology, and in particular to a test method that combines pressuremeter test and flat shovel lateral expansion test in situ. Background Technology

[0002] In geotechnical engineering investigation, in-situ testing is an important investigation method, and pressuremeter test and shovel lateral expansion test are two testing items in in-situ testing.

[0003] The pressuremeter test is an in-situ test that applies lateral horizontal pressure to the borehole wall using a pressuremeter probe, causing the borehole wall to expand outward until it fails. This allows for the determination of the relationship between pressure and borehole volume increment, and the inference of the mechanical properties of the foundation soil. While the pressuremeter test offers unique advantages as an in-situ testing method with relatively clear mechanical states, the process is complex and costly. Furthermore, due to the complexity of its boundary conditions, the test results are easily affected by factors such as borehole quality and instrument airtightness.

[0004] The shovel dilatation test is an in-situ test that uses static force to press a shovel-shaped probe into the soil. Once the test depth is reached, air pressure is used to expand a circular steel diaphragm on the side of the probe outward by a certain horizontal displacement. The air pressure acting on the inner side of the diaphragm at each displacement is recorded to obtain the soil parameters. The shovel dilatation test probe is small, causing minimal compression and disturbance to the soil during in-situ testing, resulting in relatively stable parameters. However, precisely because the shovel dilatation test has a limited influence on the soil, when soil homogeneity is poor, the test results often only represent the mechanical properties of the soil at the test point, and the results may vary significantly between different locations.

[0005] The accuracy of geotechnical investigation results directly affects the rationality and safety of foundation design. Accurate evaluation of site conditions and potential problems under special circumstances through geotechnical investigation can effectively ensure smooth construction. Eliminating interfering factors and accurately obtaining geotechnical parameters for specific soil types is crucial. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a testing method and application that combines in-situ pressure measurement test and flat shovel lateral expansion test, which solves the technical problem that geotechnical engineering investigation results are easily interfered with and have poor accuracy.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the present invention proposes an in-situ combined test method of pressure side test and flat spade lateral expansion test, including multiple sets of combined tests;

[0010] Each test includes the following steps:

[0011] S1. Set three test points along the axis of the same borehole, including the middle pressure test point, the upper flat shovel side expansion test point, and the lower flat shovel side expansion test point;

[0012] S2. Proceed with the following steps sequentially along the depth direction of the formation:

[0013] The first lateral expansion test of the flat shovel was carried out at the test point of the upper flat shovel to obtain the lateral expansion modulus E1.

[0014] A pressure meter test was conducted at the central pressure meter test point to obtain the pressure meter modulus Em.

[0015] A second lateral expansion test of the flat shovel was conducted at the test point of the lower flat shovel to obtain the lateral expansion modulus E2.

[0016] After the above-mentioned joint tests, the test depth and the pressure modulus Em, and the test depth and the average lateral expansion modulus E of the two flat chisel lateral expansion tests were established respectively. P The curve of (E1+E2) / 2;

[0017] A correlation analysis is performed on the two curves above. If the similarity is greater than the preset value, the test result is considered accurate.

[0018] A further technical solution is that step S2 includes:

[0019] The drilling and exploration were carried out using a rotary advance method to reach the in-situ testing starting position.

[0020] The probe of the flat shovel was inserted to the test point of the upper flat shovel side expansion by static pressing. After the first flat shovel side expansion test was completed, the probe was removed.

[0021] The pressure meter test hole was constructed downward from the in-situ test starting position using rotary drilling. The pressure meter test was conducted at the pressure meter test point in the middle of the pressure meter test hole using a pressure meter instrument. After completion, the pressure meter instrument was removed.

[0022] The drilling was carried out by rotating the drilling machine to the bottom of the pressure test hole. Then, the flat shovel probe was inserted into the lower flat shovel lateral expansion test point by static pressing to complete the second flat shovel lateral expansion test.

[0023] A further technical solution is that the upper flat shovel lateral expansion test point, the lower flat shovel lateral expansion test point, and the middle pressure test point are all located within the same geological unit layer, and the coefficient of variation of soil parameters between adjacent test points is less than 20%.

[0024] A further technical solution is that the distance between the starting position of the in-situ test and the test point of the upper flat shovel side expansion is not less than 20cm.

[0025] A further technical solution is that the distance between the upper flat shovel side expansion test point and the middle side pressure test point is not less than 70cm.

[0026] A further technical solution is that, in step S2, the distance between the central pressure test point and the bottom of the pressure test hole is not less than 50cm.

[0027] A further technical solution is that the penetration rate of the static pressing is controlled within the range of 1.0-2.0 cm / s, and the probe tilt angle during the penetration process is ≤2°.

[0028] A further technical solution is that the pressure-side test adopts a three-stage pressurization method, with an initial pressure stage loading rate ≤10kPa / s and a maintenance stage duration ≥60s.

[0029] A further technical solution is to use clay, silt, loess, or loose to medium-dense sandy soil as the applicable geological structure for testing.

[0030] A further technical solution is that the method is applied to geotechnical engineering investigation.

[0031] (III) Beneficial Effects

[0032] The beneficial effects of this invention are as follows: Addressing the respective advantages and disadvantages of pressuremeter tests and dilatation tests, this invention proposes a combined in-situ testing method that combines these two methods. The aim is to alternately conduct pressuremeter and dilatation tests within the same borehole, providing more accurate and reasonable geotechnical parameters through comparative analysis of the results. Both in-situ testing methods provide lateral mechanical property indicators of soil, and their results are highly correlated. This invention, by integrating these two testing methods in geotechnical engineering investigation, can significantly improve the reliability of the provided parameters, reduce errors caused by the principles and equipment of a single method, and by comparing the test results obtained from the two methods, comprehensively considering the limitations and complementary advantages of various testing methods, thus providing a more reasonable solution for the comprehensive analysis of geotechnical parameters. Attached Figure Description

[0033] Figure 1 This is a schematic diagram illustrating the implementation process of the in-situ combined pressure test and flat shovel lateral expansion test of the present invention; in the figure, A is a schematic diagram of the test position of the first flat shovel lateral expansion test; B is a schematic diagram of the test position of the pressure test; and C is a schematic diagram of the test position of the second flat shovel lateral expansion test.

[0034] Figure 2This is a graph showing the variation of the pressure modulus Em with the test depth during the pressuremeter test.

[0035] Figure 3 The lateral expansion modulus E of the flat spade lateral expansion test D Curve showing the change with test depth.

[0036] Figure 4 for Figure 2 and Figure 3 The average lateral expansion modulus E of two consecutive lateral expansion tests of a flat spade P Correlation comparison test curves under the same coordinate system.

[0037] [Attached image labels]

[0038] 1: Exploration borehole; 2: In-situ test starting position; 3: Upper flat shovel lateral expansion test point; 4: Side pressure test hole; 5: Middle side pressure test point; 6: Lower flat shovel lateral expansion test point. Detailed Implementation

[0039] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present invention can be understood more clearly and thoroughly, and that the scope of the present invention can be fully conveyed to those skilled in the art.

[0040] This embodiment provides a method for in-situ combined pressuremeter test and shovel lateral expansion test, including the following steps: First, three test points are set along the axial direction of the same borehole, including a middle pressuremeter test point 5, an upper shovel lateral expansion test point 3, and a lower shovel lateral expansion test point 6. Second, the following steps are performed sequentially along the formation depth direction: a first shovel lateral expansion test is conducted at the upper shovel lateral expansion test point 3 to obtain the lateral expansion modulus E1; a pressuremeter test is conducted at the middle pressuremeter test point 5 to obtain the pressuremeter modulus Em; and a second shovel lateral expansion test is conducted at the lower shovel lateral expansion test point 6 to obtain the lateral expansion modulus E2. Third, after multiple sets of combined tests, curves are established for the test depth versus the pressuremeter modulus Em and the test depth versus the average lateral expansion modulus EP = (E1 + E2) / 2 from the two shovel lateral expansion tests. Fourth, correlation analysis is performed on the two curves. If the similarity is greater than a preset value, the test result is considered accurate. In this embodiment, the preset value is 90%.

[0041] In step one above, the borehole refers to exploration borehole 1, specifically a circular hole drilled downwards from the ground surface using specialized drilling equipment in the field of geotechnical engineering exploration to ascertain the geological and hydrogeological conditions of the construction site and its surroundings. This embodiment primarily tests the lateral mechanical properties of the strata. In-situ tests are conducted at a specified depth within exploration borehole 1 according to the technical requirements for in-situ testing. Joint tests are conducted in groups, with each group of in-situ tests including one pressuremeter test and two dilatation tests. The pressuremeter test is located midway between the two dilatation test locations. Preferably, the pressuremeter test is located precisely in the center of the two dilatation test locations, as this provides a more representative representation of the geological strata's performance parameters at that location.

[0042] Step two above further includes: drilling exploration borehole 1 using a rotary drilling method to the in-situ test starting position 2. Using a static pressing method, inserting the flat-blade probe to the upper flat-blade lateral expansion test point 3, and removing the probe after completing the first flat-blade lateral expansion test. Continuing downwards from the in-situ test starting position 2, drilling the pressure-side test hole 4 using a rotary drilling method, and conducting a pressure-side test at the middle pressure-side test point 5 of the pressure-side test hole 4 using a pressure-side instrument, then removing the pressure-side instrument. Drilling exploration borehole 1 to the bottom of the pressure-side test hole 4 using a rotary drilling method, and then using a static pressing method, inserting the flat-blade probe to the lower flat-blade lateral expansion test point 6 to complete the second flat-blade lateral expansion test. Rotary drilling refers to a drilling method in which the drill string and the drill bit at the bottom are driven to rotate at high speed by the drilling rig. The cutting edge of the drill bit cuts, grinds, and breaks the rock or soil at the bottom of the hole, while the broken rock cuttings are carried out of the borehole by circulating media, thus achieving continuous drilling into the ground. The borehole wall of the exploration borehole 1 drilled by this method is relatively regular and smooth, which is conducive to ensuring the uniformity and stability of the test results. Static pressure penetration refers to the penetration process in which no dynamic force such as impact, vibration, or rotation is used. Instead, the probe is vertically pressed into the formation by a stable and continuously increasing static pressure applied by mechanical equipment.

[0043] In this embodiment, in-situ combined testing is conducted using pressuremeter tests and shovel dilatation tests. The pressuremeter tests and shovel dilatation tests are performed alternately, and by reasonably selecting the interval between adjacent test locations, the average depth of two adjacent shovel dilatation tests is consistent with the depth of the intermediate pressuremeter test. Thus, the influence of different formation depths on the test results can be eliminated by taking the average of the test results. Furthermore, the test results of the pressuremeter tests and shovel dilatation tests can be comprehensively compared and analyzed, eliminating the test error of a single test method and improving the accuracy of the test results.

[0044] In this embodiment, the upper flat shovel lateral dilatation test point 3, the lower flat shovel lateral dilatation test point 6, and the middle pressuremeter test point 5 are all located within the same geological unit layer, and the coefficient of variation of soil parameters between adjacent test points is less than 20%. Since on-site testing will cause some disturbance to the surrounding strata, a spacing should be set between the in-situ test points to ensure that the test points do not affect each other. The distance between the in-situ test starting position 2 and the upper flat shovel lateral dilatation test point 3 is not less than 20cm, preferably 20cm in this embodiment. The distance between the upper flat shovel lateral dilatation test point 3 and the middle pressuremeter test point 5 is not less than 70cm, preferably 70cm in this embodiment. The distance between the middle pressuremeter test point 5 and the bottom of the pressuremeter test hole 4 is not less than 50cm, preferably 50cm in this embodiment.

[0045] This embodiment fundamentally ensures the stratigraphic representativeness of the data by strictly controlling all tests within a homogeneous geological unit and ensuring the high stability of adjacent soil properties. The distance between the upper flat shovel lateral dilatation test and the borehole opening effectively isolates the borehole opening disturbance effect.

[0046] The spacing between the upper flat shovel lateral expansion test and the pressuremeter test avoids interference between the stress fields of the two tests; the distance between the pressuremeter probe and the bottom of the borehole ensures that the test section avoids interference from the bottom of the lower borehole layer. This ultimately results in high-precision geotechnical parameters covering the entire borehole depth without undisturbed superposition.

[0047] In this embodiment, preferably, the penetration rate of the static pressure test is controlled within the range of 1.0-2.0 cm / s, and the probe tilt angle during penetration is ≤2°. The pressuremeter test adopts a three-stage pressure method, with an initial pressure stage loading rate ≤10 kPa / s and a maintenance stage duration ≥60 s. This embodiment ensures that the probe resistance truly reflects the in-situ soil strength by limiting the uniform penetration range of the static pressure test and the vertical accuracy of the probe; the low tilt angle helps to eliminate test deviations. Controlling the loading rate in the initial pressure stage helps to simulate the actual loading process of the foundation, and the maintenance stage ensures the complete release of the soil consolidation response.

[0048] The method described in this embodiment is primarily applied in the technical field of geotechnical engineering investigation. The applicable geological structures for this testing method are cohesive soil, silt, loess, or loose to medium-dense sand. The pressuremeter test is suitable for cohesive soil, silt, sand, gravelly soil, residual soil, weathered rock, and soft rock where the borehole walls can remain stable, but not for saturated soft clay. The shovel dilatation test is suitable for soft soil, general cohesive soil, silt, loess, and loose to medium-dense sand. In dense sand, miscellaneous fill, gravelly layers, and weathered rock, the diaphragm of the shovel is easily damaged, so it is generally not suitable. This invention combines the pressuremeter test and the shovel dilatation test in situ. The tested soil must simultaneously meet the applicable conditions of both tests; therefore, this invention selects general cohesive soil, silt, loess, or loose to medium-dense sand as the test soil.

[0049] Repeating step two yields multiple sets of in-situ joint test results. This embodiment conducted a total of 8 sets of joint tests, each including two lateral expansion tests and one pressure test. The distance between the upper lateral expansion test point 3 and the middle pressure test point 5 was 70 cm, and the distance between the middle pressure test point 5 and the lower lateral expansion test point 6 was also 70 cm. The pressure modulus Em at different test depths, the lateral expansion moduli E1 and E2 of the two lateral expansion tests, and the average lateral expansion modulus EP = (E1 + E2) / 2 were then recorded in the table below.

[0050]

[0051]

[0052] Establish the relationship between test depth and pressure modulus Em, and the relationship between test depth and average lateral expansion modulus E from two flat chisel lateral expansion tests. P The curve of (E1+E2) / 2. The data curve of the pressuremeter modulus Em as a function of test depth in the pressuremeter test is shown below. Figure 2 Lateral expansion modulus E of two flat chisel lateral expansion tests D Data curve reference with test depth Figure 3 , Figure 4 for Figure 2 and Figure 3 The average lateral expansion modulus E of two consecutive lateral expansion tests of a flat spade P Correlation comparison test curves under the same coordinate system.

[0053] from Figure 2 and Figure 3 The test curves show that, with changes in test depth and test formation, the pressure modulus Em from the pressuremeter test and the average dilatation modulus E from the two shovel dilatation tests increase. P They exhibit similar patterns of change.

[0054] Combining the measured data in Table 1 and Figure 4 The comparative test curves show that, after averaging the test results of the two lateral expansion tests in each group of joint tests, the lateral compression modulus Em at different depths and the average lateral expansion modulus E of the two lateral expansion tests are significantly different. P The correlation is very obvious.

[0055] Furthermore, in this embodiment, the use of terms such as "first" and "second" is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of those features. In the description of this embodiment, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0056] It should be understood that the above description of specific embodiments of the present invention is only for illustrating the technical approach and features of the present invention, and is intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. However, the present invention is not limited to the specific embodiments described above. All changes or modifications made within the scope of the claims of the present invention should be covered within the protection scope of the present invention.

Claims

1. A test method for in-situ combining pressuremeter test and shovel lateral expansion test, characterized in that, Includes at least one set of joint tests; The joint test includes the following steps: S1. Set three test points along the axis of the same borehole, including the middle side pressure test point (5), the upper flat shovel side expansion test point (3) and the lower flat shovel side expansion test point (6). S2. Proceed with the following steps sequentially along the depth direction of the formation: The first lateral expansion test of the flat shovel was carried out at the test point (3) on the upper flat shovel to obtain the lateral expansion modulus E1; A pressure test was conducted at the pressure test point (5) in the middle section to obtain the pressure modulus Em. A second lateral expansion test was conducted at the lower lateral expansion test point (6) to obtain the lateral expansion modulus E2. Establish curves of test depth versus pressure modulus Em and test depth versus average lateral expansion modulus EP = (E1 + E2) / 2 of two adjacent flat shovel lateral expansion tests; A correlation analysis is performed on the two curves above. If the similarity is greater than the preset value, the test result is considered accurate.

2. The in-situ combined pressure-side test and flat-blade lateral expansion test method according to claim 1, characterized in that, Step S2 includes: The drilling (1) was carried out using a rotary drilling method to the in-situ test starting position (2); The probe of the flat shovel was inserted to the upper flat shovel side expansion test point (3) by static pressing. After the first flat shovel side expansion test was completed, the probe was removed. The pressure test hole (4) was constructed downward from the in-situ test starting position (2) using rotary drilling. The pressure test was conducted at the pressure test point (5) in the middle of the pressure test hole (4) using a pressure test instrument. After completion, the pressure test instrument was removed. The drilling and exploration borehole (1) was constructed using a rotary drilling method to the bottom position of the side pressure test hole (4). The flat shovel probe was inserted into the lower flat shovel side expansion test point (6) using a static pressing method to complete the second flat shovel side expansion test.

3. The in-situ combined test method of pressure-side test and flat spade lateral expansion test according to claim 2, characterized in that, The upper flat shovel lateral expansion test point (3), the lower flat shovel lateral expansion test point (6), and the middle pressure test point (5) are all located within the same geological unit layer, and the coefficient of variation of soil parameters between adjacent test points is less than 20%.

4. The in-situ combined test method of pressure-side test and flat spade lateral expansion test according to claim 2, characterized in that, The distance between the starting position (2) of the in-situ test and the test point (3) of the upper flat shovel side expansion test shall not be less than 20cm.

5. The in-situ combined test method of pressure-side test and flat spade lateral expansion test according to claim 2, characterized in that, The distance between the upper flat shovel side expansion test point (3) and the middle side pressure test point (5) shall not be less than 70cm.

6. The in-situ combined test method of pressure-side test and flat spade lateral expansion test according to claim 2, characterized in that, In step S2, the distance between the middle pressure test point (5) and the bottom of the pressure test hole (4) is not less than 50cm.

7. The in-situ combined test method of pressure-side test and flat spade lateral expansion test according to claim 2, characterized in that, The penetration rate of the static pressing is controlled within the range of 1.0-2.0 cm / s, and the probe tilt angle during the penetration process is ≤2°.

8. The in-situ combined test method of pressure-side test and flat spade lateral expansion test according to claim 2, characterized in that, The pressure-meter test adopts a three-stage pressurization method, with an initial pressure stage loading rate ≤10kPa / s and a maintenance stage duration ≥60s.

9. The in-situ combined test method of pressure-side test and flat spade lateral expansion test according to claim 1, characterized in that, The applicable geological structures for the test are cohesive soil, silt, loess, or loose to medium-dense sand.

10. The in-situ combined test method of pressuremeter test and lateral expansion test according to any one of claims 1-8, characterized in that, The method is applied to geotechnical engineering investigation.

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