Test clay structure and horizontal uniaxial compression test method using the same

Abstract

To provide a viscous soil structure for testing to accurately obtain horizontal resistance by correctly reflecting an actual condition of an original ground, and also to provide a horizontal uniaxial compression test method using the same.SOLUTION: A viscous soil structure for testing is formed of viscous soil which is collected in a horizontal direction with respect to a laminated ground containing viscous soil and continues in a horizontal direction of a stratum of the laminated ground.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a test viscous soil structure as viscous soil for civil engineering strength tests, and particularly to a test viscous soil structure capable of realizing a high-precision uniaxial compression test and a horizontal uniaxial compression test method using the same.

Background Art

[0002] When installing foundation piles, steel sheet piles, etc. in a viscous soil ground, in order to ensure safety and strength, prior design regarding the number of foundation piles to be installed and the selection of the type of steel sheet piles is carried out by measuring and evaluating the horizontal resistance acting on these structural materials.

[0003] [[ID=1⑤]] In this case, as an index value reflecting the horizontal resistance of the viscous soil ground, the deformation coefficient (Young's modulus) becomes an important specification. As in-situ tests for obtaining this, both an in-hole horizontal loading test (Soil Engineering Society Standard JGS 1421) and, as an indoor test, a uniaxial compression test based on Japanese Industrial Standards (JIS A 1216) are being carried out.

[0004] Since the in-hole horizontal loading test is an in-situ test using a boring hole, it is easily affected by stress relief and disturbance during sample collection, and it is known that the deformation coefficient tends to be underestimated and the result is uneconomical in design. Also, since it is difficult to directly grasp the degree of that disturbance, there are also problems in verifying the results.

[0005] On the other hand, in the uniaxial compression test, by compressing a specimen sampled from a viscous soil ground, the maximum value of the correlation curve between the measured compression stress and compression strain is defined as the uniaxial compression strength and evaluated. Also, the initial linear gradient part of this correlation curve is defined as the deformation coefficient and evaluated. Thus, since it is an indoor test capable of simultaneously measuring the compression stress and compression strain, it is possible to directly grasp the influence of disturbance, and when good sampling and specimen preparation are possible, it is currently considered to be a test method that reflects the actual state of the original ground.

[0006] Accurately calculating the unconfined compressive strength, which serves as a quality standard, is a major safety concern in civil engineering projects. For this reason, various unconfined compression tests using unconfined compressive strength have been studied for the purpose of determining the quality standards of fluidized soil.

[0007] For example, in a conventional uniaxial compression test, a method for determining the quality standard of fluidized treated soil, which is produced by mixing soil to be treated, a solidifying agent, and adjusted slurry or water with adjusted specific gravity, is known. This method compares 1.1 times the average effective confining pressure at the location where the fluidized treated soil is placed, the ground strength at the location where the fluidized treated soil is placed, and the deviation stress of vertical stress and horizontal stress at the location where the fluidized treated soil is placed, and determines the uniaxial compressive strength that serves as the quality standard for the fluidized treated soil based on the largest value (see Patent Document 1).

[0008] Furthermore, in conventional uniaxial compression tests, the aim is to estimate the uniaxial compressive strength of soil from measured values ​​using a rotational penetration test. In this test, a penetration rod with a screw point at its tip is rotated and driven into the ground, and the rotational torque T of the penetration rod is measured while gradually changing the load W applied to the penetration rod. Based on the dimensions of the screw point, the horizontal shear stress τ acting on the surface of the screw point is measured. h The relationship between the rotational torque T and the horizontal shear stress τ is determined, and when the load W applied to the penetration rod is zero, the horizontal shear stress τ h A method is known for calculating the uniaxial compressive strength of soil by determining the relationship between the shear stress τ acting on the surface of the screw point and the rotational torque under zero load based on the relationship equation, and then applying Mohr's stress circle theory to the relationship equation (see Patent Document 2). [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2005-105577 [Patent Document 2] Japanese Patent Publication No. 2014-134067 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] In conventional uniaxial compression tests, as described in Patent Documents 1 and 2 above, in order to collect a sample that maintains the geological condition at a predetermined location in the cohesive soil as much as possible, a sampling tube is pressed into the cohesive soil vertically (thin-wall sampling), and the resulting sample is then molded into a cylindrical shape to create a test specimen.

[0011] Therefore, conventional uniaxial compression tests inherently have a problem: the better the specimen is prepared and free of disturbances, the more the uniaxial compressive strength and deformation modulus are overestimated when considering the anisotropy of the ground, leading to dangerous results in terms of design.

[0012] Currently, the design assumes that another factor will offset the decrease in strength due to stress release in the specimen, and therefore, the aforementioned problems are not particularly considered during the design phase. In other words, although it is known that conventional uniaxial compression tests have problems with measurement accuracy, this is currently tolerated.

[0013] There is a need to improve the current methods of in-situ horizontal loading tests and unconfined compression tests, which do not accurately reflect the actual conditions of the ground, and to develop a test method that can accurately determine horizontal resistance. However, no such unconfined compression test method exists yet. In addition, high-quality test cohesive soil structures that can be used in such an unconfined compression test method are also unknown.

[0014] This invention was made to solve the aforementioned problems and aims to provide a test cohesive soil structure that accurately reflects the actual conditions of the ground and allows for highly accurate determination of horizontal resistance, as well as a horizontal uniaxial compression test method using the same. [Means for solving the problem]

[0015] The test cohesive soil structure disclosed in this application is collected horizontally from a layered ground containing cohesive soil and is formed from cohesive soil that is continuous horizontally in the layers of the said layered ground. In this way, the test cohesive soil structure disclosed in this application is collected horizontally from a layered ground containing cohesive soil and is formed from cohesive soil that is continuous horizontally in the layers of the said layered ground. As such, it maintains a state that faithfully reflects the state of the horizontal layers of the said layered ground, and can accurately reflect the actual state of the layered ground as a test cohesive soil structure suitable for accurately determining the horizontal resistance of the ground by horizontal uniaxial compression tests, etc.

[0016] Furthermore, the horizontal uniaxial compression test method disclosed herein includes a receiving step of penetrating a hollow penetrating cylinder vertically into a layered ground containing cohesive soil and accommodating the cohesive soil in the penetrating cylinder; a forming step of removing a cylindrical test cohesive soil structure made of the cohesive soil accommodating the penetrating cylinder and shaping it along the short direction from a predetermined position in the longitudinal direction of the penetrating cylinder; a measurement step of measuring the deformation coefficient of the test cohesive soil structure; and an evaluation step of evaluating the horizontal resistance of the ground based on the deformation coefficient.

[0017] Thus, the process includes a filling step in which a hollow penetrating cylinder is vertically inserted into a layered ground containing cohesive soil and the cohesive soil is contained within the penetrating cylinder; a molding step in which a cylindrical test cohesive soil structure made of the cohesive soil contained within the penetrating cylinder is removed and shaped along the short side from a predetermined position in the longitudinal direction of the penetrating cylinder; a measurement step in which the deformation coefficient of the test cohesive soil structure is measured; and an evaluation step in which the horizontal resistance of the ground is evaluated based on the deformation coefficient. As a result, the test cohesive soil structure, which is formed while maintaining the horizontal soil condition of the layered ground by the molding step, is used in the measurement step to measure the deformation coefficient of the test cohesive soil structure, and the horizontal resistance of the ground is evaluated in the evaluation step based on the deformation coefficient, thereby enabling accurate determination of the horizontal resistance of the ground.

[0018] In addition, in the horizontal uniaxial compression test method disclosed in the present application, one or more markings are provided along the longitudinal direction of the penetration cylinder as required, and the forming process is to take out and form the test viscous soil structure along the short direction from the marking of the penetration cylinder. Thus, since one or more markings are provided along the longitudinal direction of the penetration cylinder and the forming process is to take out and form the test viscous soil structure along the short direction from the marking of the penetration cylinder, the depth of the layered ground is determined for each marking, and the horizontal resistance of the ground in the horizontal direction for each depth is evaluated, and the horizontal resistance of the ground can be accurately obtained in multiple layers.

[0019] In addition, the test viscous soil structure disclosed in the present application is formed by the forming process of the above horizontal uniaxial compression test method as required. Thus, since it is formed by the forming process of the above horizontal uniaxial compression test method, the state that faithfully reflects the state of the horizontal layers of the layered ground as it is is maintained by the forming of the forming process, and as a test viscous soil structure suitable for accurately obtaining the horizontal resistance such as the horizontal uniaxial compression test, the actual situation of the layered ground can be accurately reflected.

Brief Description of Drawings

[0020] [Figure 1] The configuration diagram of the test viscous soil structure according to the first embodiment of the present invention is shown. [Figure 2] The flowchart of the horizontal uniaxial compression test method according to the first embodiment of the present invention is shown. [Figure 3] The configuration diagram of the test viscous soil structure according to the first embodiment of the present invention is shown. [Figure 4] The explanatory diagram of the forming using the forming processing device of the test viscous soil structure according to the first embodiment of the present invention is shown. [Figure 5] The explanatory diagram of the forming using the forming processing device of the test viscous soil structure according to the first embodiment of the present invention is shown. [Figure 6] The explanatory diagram of the forming using the forming processing device of the test viscous soil structure according to the first embodiment of the present invention is shown. [Figure 7]The diagrams and explanatory figures of the test cohesive soil structure according to the first embodiment of the present invention are shown. [Figure 8] This diagram shows the configuration of a test cohesive soil structure according to a second embodiment of the present invention. [Figure 9] This diagram shows the configuration of a test cohesive soil structure according to another embodiment of the present invention. [Modes for carrying out the invention]

[0021] (First Embodiment) As shown in Figure 1, the test cohesive soil structure 1a according to the first embodiment of the present application is collected horizontally (in the X direction) from a layered ground 100 containing cohesive soil, and is formed from cohesive soil that is continuous in the horizontal direction (in the X direction) of the strata of the layered ground 100. As a result, the test cohesive soil structure 1a according to the first embodiment of the present application maintains a state in which it receives the horizontal resistance A in the horizontal direction (in the X direction) of the layered ground 100 along its longitudinal direction.

[0022] Examples of layered ground containing cohesive soil 100 include riverbeds. Industrially, civil engineering works on riverbeds are important both from a landscape and safety perspective, and the accuracy of strength measurements is therefore crucial.

[0023] Thus, as shown in Figure 1, the test cohesive soil structure 1a disclosed in this application is collected horizontally (in the X direction) from a layered ground 100 containing cohesive soil, and is formed from cohesive soil that is continuous in the horizontal direction (X direction) of the layers of the layered ground 100. As such, it faithfully maintains a state that reflects the state of the layers in the horizontal direction (X direction) of the layered ground 100, and can accurately reflect the actual state of the layered ground 100 as a test cohesive soil structure 1a suitable for accurately determining the horizontal resistance A of the ground by horizontal uniaxial compression tests, etc.

[0024] The horizontal uniaxial compression test method using this test cohesive soil structure 1a will be explained below in accordance with the flowchart shown in Figure 2.

[0025] First, as shown in Figure 2, a hollow penetrating cylinder is driven vertically into the layered ground 100 containing cohesive soil, and as shown in Figure 3(a), the cohesive soil is contained within the penetrating cylinder (S1: containment process). This penetration is not particularly limited, but for example, a rotary boring machine that excavates the layered ground 100 while rotating the tip of the rod can be used.

[0026] Next, as shown in Figure 3(a), a cylindrical specimen 10 (thin wall sampling sample) made of cohesive soil contained in the penetration cylinder is removed along the vertical direction Y (direction B), and as shown in Figure 3(b), it is shaped along the short direction from a predetermined position in the longitudinal direction of the penetration cylinder, and as shown in Figure 3(c), a cylindrical test cohesive soil structure 1a is obtained (S2: shaping process). Since this test cohesive soil structure 1a is shaped along the short direction of the penetration cylinder, the longitudinal direction of the cylinder is formed along the horizontal direction (X direction) of the layered ground 100 containing cohesive soil. As a result, the longitudinal direction of the cylinder maintains the layered state in the horizontal direction (X direction) of the layered ground 100 containing cohesive soil, and the horizontal resistance in the horizontal direction (X direction) of the layered ground 100 can be directly measured.

[0027] In this molding process, although not particularly limited, a more specific method is to first use a molding apparatus 200 as shown in Figure 4(a) to horizontally position the cut specimen 10. As such a molding apparatus 200, standard products called trimmers or trimming devices can be obtained from the market and used.

[0028] Next, as shown in Figure 4(b), the front and back surfaces of the cut specimen 10 are trimmed. Specifically, the upper base surface 10a and the lower base surface 10b of the cylindrical shape of the cut specimen 10 are trimmed away. The bottom surface of the disc-shaped cut specimen 10 is generally unstable when installed, but this bottom surface configuration prevents damage to the cut specimen 10 during the initial trimming stage.

[0029] As shown in Figure 5(a), a wedge-shaped rubber plate 203, devised by the inventors, is placed on the base 201 to stabilize it, and this wedge-shaped rubber plate 203 is sandwiched under the cut specimen 10 that is placed on it to stabilize the bottom surface. Maintaining this state, the cut specimen 10 is trimmed and shaped as shown in Figure 5(b). That is, the left side surface 10c and the right side surface 10d of the cylindrical shape of the cut specimen 10 are trimmed away. This makes it possible to prevent the specimen from collapsing when the sides of the cut specimen 10 are trimmed.

[0030] The subsequent procedure for preparing cylindrical specimens can be carried out in accordance with the uniaxial compression test for soil (JIS A 1216).

[0031] First, as shown in Figure 6(a), the wedge-shaped rubber plate 203 is removed from the base 201, and the entire cylinder of the cut specimen 10, which is sandwiched between the base 201 and the upper surface fixing part 202, is rotated to perform trimming.

[0032] As shown in Figure 6(b), the dimensions are adjusted within the opposing U-shaped miter boxes 204 to trim the end faces of the cut specimen 10, and as shown in Figure 6(c), the test cohesive soil structure 1a as a cylindrical specimen is completed. This test cohesive soil structure 1a can be made to any desired size depending on the purpose, for example, it can be made into a cylindrical shape with a height of 63 mm and a diameter of 35 mm.

[0033] The cylindrical specimen of the test cohesive soil structure 1a obtained in this way is cut and formed from a cut specimen 10 (thin wall sampling sample) aligned with the vertical direction (Y direction) of the layers of the laminated ground 100, as shown in Figure 7(a), and its cylindrical length coincides with the horizontal direction (X direction) of the layers of the laminated ground 100. For example, as shown in Figure 7(b), a test cohesive soil structure 1a with a diameter of 35 mm and a length of 63 mm can be obtained from a cut specimen 10 (thin wall sampling sample) with a diameter of 75 mm.

[0034] In this context, thin-wall sampling, a method commonly used at construction sites, has a proven track record as a method that produces less sample disturbance compared to block sampling and is effective even for sampling from deep geological formations exceeding 10 meters in depth.

[0035] On the other hand, in order to accurately determine the horizontal reaction force within the ground, it would be ideal to perform thin-wall sampling in the horizontal direction of the ground and then conduct uniaxial compression tests using the specimens cut from these samples. However, in actual field work, this sampling method is not easily implemented due to issues with equipment, labor, and cost. In particular, it is extremely difficult to collect horizontal samples from deep ground involving foundation piles or steel sheet piles, and therefore it is not carried out in normal work.

[0036] In this regard, the horizontal uniaxial compression test method using the test cohesive soil structure 1a according to the first embodiment of the present application is improved in the method of cutting out specimens from the vertical thin-wall sampling sample that is normally performed, and an ideal uniaxial compression test can be performed using the cut-out specimens.

[0037] The stress and strain of the test cohesive soil structure 1a, prepared as a cylindrical specimen, can also be measured in accordance with the uniaxial compression test for soil (JIS A 1216). Specifically, the deformation modulus of this test cohesive soil structure 1a is measured according to the uniaxial compression test for soil (JIS A 1216) (S3: Measurement process). Next, the horizontal resistance of the ground is evaluated based on this deformation modulus, according to the uniaxial compression test for soil (JIS A 1216) (S4: Evaluation process).

[0038] Thus, the process includes a filling step in which a hollow penetrating cylinder is vertically penetrated into the layered ground 100 containing cohesive soil, and the cohesive soil is contained within the penetrating cylinder; a forming step in which a cylindrical test cohesive soil structure 1a made of the cohesive soil contained within the penetrating cylinder is removed and shaped along the short side from a predetermined position in the longitudinal direction of the penetrating cylinder; a measurement step in which the deformation modulus of the test cohesive soil structure 1a is measured; and an evaluation step in which the horizontal resistance of the ground is evaluated based on this deformation modulus. Therefore, the test cohesive soil structure 1a, which is formed while maintaining the horizontal soil condition of the layered ground 100 by the forming step, is used, the measurement step in which the deformation modulus of the test cohesive soil structure 1a is measured, and the evaluation step in which the horizontal resistance of the ground is evaluated based on this deformation modulus, thereby enabling accurate determination of the horizontal resistance of the ground.

[0039] Thus, since the test cohesive soil structure 1a disclosed in this application is formed by the molding process of the horizontal uniaxial compression test method described above, the molding process maintains a state that faithfully reflects the horizontal state of the geological layers of the layered ground 100. As a test cohesive soil structure 1a suitable for accurately determining horizontal resistance in horizontal uniaxial compression tests, etc., it can accurately reflect the actual state of the layered ground 100.

[0040] (Second embodiment) The horizontal uniaxial compression test method according to the second embodiment of the present application includes the receiving step, the molding step, the measurement step, and the evaluation step, similar to the first embodiment, and further, as shown in Figure 8, one or more markers are inscribed along the longitudinal direction of the penetration cylinder, and the molding step involves taking out the test clay structure 1a along the short direction from the markers of the penetration cylinder and molding it.

[0041] As shown in Figure 8(a), line-shaped markers can be used as these markers, and by placing these markers at equal intervals, as shown in Figure 8(b), the test cohesive soil structure 1a can be extracted and formed for each marker. As a result, as shown in Figure 8(c), test cohesive soil structures 1a, 1b, and 1c can be obtained for each depth of the layered ground 100.

[0042] By using a test cohesive soil structure 1a obtained by maintaining the horizontal layering conditions at each depth of the layered ground 100, it becomes possible to easily measure the horizontal resistance value (direction A) corresponding to each depth. This accurate horizontal resistance value at each depth is impossible to measure with conventional samples thin-walled sampling along the vertical direction.

[0043] Thus, one or more markers are inscribed along the longitudinal direction of the penetration cylinder, and the molding process involves extracting and molding the test cohesive soil structure 1a along the short direction from these markers on the penetration cylinder. As a result, the depth of the layered ground 100 is determined for each marker, and the horizontal resistance of the ground in the horizontal direction at each depth is evaluated, allowing for accurate and multi-layered determination of the horizontal resistance of the ground.

[0044] (Other embodiments) In other embodiments, the layered ground 100 containing cohesive soil can be configured to be particularly suitable for measuring strong resistance from slopes, especially when the layered ground 100 has slopes, such as in riverbeds.

[0045] In other words, the test clay structure 1a according to other embodiments of the present application includes the same receiving step, the molding step, the measurement step, and the evaluation step as in the first embodiment, and further, as shown in Figure 9, the molding step involves taking out the cylindrical test clay structure 1a made of clay contained in the penetration cylinder and molding it along the slope direction (direction C) of the laminated ground 100 from a predetermined position in the longitudinal direction of the penetration cylinder.

[0046] In this way, the cylindrical test clay structure 1a is removed and formed along the slope direction (direction C) of the layered ground 100 from a predetermined position in the longitudinal direction of the penetration cylinder. As a result, the test clay structure 1a is suitable for measuring strong resistance from the slope direction (direction C) when the layered ground 100 containing clay has a slope, especially in riverbeds, and can be used for strength measurement according to the purpose and location.

[0047] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0048] (Example 1) Three borings were conducted on the slope of an agricultural irrigation canal in Morotomi-cho, Saga City, Saga Prefecture, and vertical thin-wall sampling was obtained. A cylindrical test cohesive soil structure was extracted and formed according to the first embodiment described above. Design calculations were performed for the steel sheet pile section to calculate the deformation modulus of the ground. Normally, a uniaxial compression test is performed with three samples, but if the data variability is large (about twice as large), the number of samples was increased to five, and the number of samples was added as needed.

[0049] The deformation modulus was measured using a uniaxial compression test (horizontal), a uniaxial compression test (vertical), and an in-situ horizontal loading test. The measurement results at a depth of 4.50 to 5.40 m below the ground surface are shown in the table below.

[0050] [Table 1]

[0051] qu(V): Compressive strength (kN / m) obtained by uniaxial compression test (vertical) 2 ) εf(V): Fracture strain (%) from uniaxial compression test (vertical) E50(V): Deformation modulus (kN / m) obtained by uniaxial compression test (vertical) 2 ) Em: Deformation modulus (kN / m) obtained by horizontal load testing in boreholes (LLT) 2 ) qu(H): Compressive strength (kN / m) obtained by uniaxial compression test (horizontal) 2 ) εf(H): Fracture strain (%) from uniaxial compression test (horizontal) E50(H): Deformation modulus (kN / m) obtained by uniaxial compression test (horizontal) 2 )

[0052] The results showed that the deformation modulus obtained from the uniaxial compression test (horizontal) was smaller than that obtained from the uniaxial compression test (vertical), and that it produced a stable value that was faithful to the horizontal resistance value, confirming that it is indeed a highly accurate indicator value. [Explanation of symbols]

[0053] 100 Layered ground 200 Molding processing equipment 201 Pedestal 202 Top fixed part 203 Rubber sheet 204 Miter Box 1a Test clay structure 1b Test clay structure 1c Test clay structure 10 Cut specimens 10a Upper base of the cylinder 10b Lower base of the cylinder 10c Left side of the cylinder 10d Right side of the cylinder

Claims

1. A filling step involves inserting a hollow penetrating cylinder, which has one or more markers inscribed on it, vertically and longitudinally along the layered ground containing cohesive soil, and filling the penetrating cylinder with cohesive soil as a result of the penetration. A molding step is performed to remove the cylindrical test clay structure made of clay contained in the penetration cylinder, and to shape it along the short direction from the mark in the longitudinal direction of the penetration cylinder, A measurement step for measuring the deformation modulus of the aforementioned test cohesive soil structure, An evaluation step to evaluate the horizontal resistance of the ground based on the deformation coefficient, Features that include Horizontal uniaxial compression test method.

2. A filling process involves vertically penetrating a hollow penetrating cylinder into a layered ground containing cohesive soil, and thereby containing the cohesive soil within the penetrating cylinder. A molding process is performed in which a cylindrical test clay structure made of clay contained in the penetration cylinder is removed, the top and bottom surfaces and sides of the cylindrical test clay structure are trimmed, and the structure is formed along the short side from a predetermined position in the longitudinal direction of the penetration cylinder, A measurement step for measuring the deformation modulus of the aforementioned test cohesive soil structure, An evaluation step to evaluate the horizontal resistance of the ground based on the deformation coefficient, Features that include Horizontal uniaxial compression test method.

3. In the horizontal uniaxial compression test method described in claim 2, One or more markings are inscribed along the longitudinal direction of the aforementioned penetration cylinder. The molding process is characterized by extracting and molding the test clay structure along the shorter direction from the mark on the penetration cylinder. Horizontal uniaxial compression test method.

Images