JP5320081B2 - Penetration test method - Google Patents

Description

  The present invention relates to a penetration test method for detecting a load when penetrating into the ground and a rotational load torque during rotation by applying a load to a penetrating rod composed of a rod and a screw point attached to the tip of the rod.

  Conventionally, as a means for knowing the degree of firmness and tightness of the ground, the geological structure of the ground, that is, the soil quality from the ground surface to a certain depth has been investigated. Such soil surveys are generally performed using a standard penetration test method based on a boring survey. One of the methods for determining the soil quality in the previous stage or a relatively shallow part is a Swedish sounding test method. This Swedish sounding test measures the hardness of the ground by measuring its resistance when the screw point attached to the rod penetrates the ground. As shown in Non-Patent Document 1 (JIS A1221 Geotechnical Society), the penetration method is a load stage in which so-called self-penetration is carried out with only a load by applying loads up to 1 KN up to a maximum of 1 KN, and a maximum load of 1 KN. In the case where the rod does not penetrate, the rod or screw point is rotated under the load, and so-called rotational penetration is performed. The measurement items corresponding to the penetration resistance are the load (Wsw) when the screw point penetrates a predetermined depth (every 25 cm penetration) at the load stage, and the half rotation number of the screw point converted per 1 m penetration (at the rotation stage) Nsw).

  However, the Swedish sounding test has drawbacks that it is difficult to distinguish soil because it is difficult to collect soil, and that empirical techniques and abilities are required to interpret the test results. Regarding the latter in particular, it has been pointed out that Nsw (half rotations / m) does not have a unit of stress or load, so the relationship with another measurement item, Wsw (N), is unclear. Yes. That is, there is a problem that the data obtained at the loading stage and the data obtained at the rotating stage are not related, and the relative strength of the self-sinking ground and the rotating ground cannot be compared. For example, when comparing a clay layer with Nsw of 50 and a clay layer with Wsw of 1000 N, rotational penetration to obtain Nsw is performed with a load of 1000 N of Wsw applied to the rod or screw point. In this case, it can be understood that the clay layer with Nsw of 50 is tighter than the clay layer with Wsw of 1000 N. However, it is not possible to make a comparative judgment up to the strength. In other words, even if the relationship between hardness and softness can be grasped qualitatively, their strength cannot be compared quantitatively. This is likely to become a barrier in the future when trying to obtain a relationship with the amount of land subsidence from the accumulated test results, or when trying to use the test results at a high level.

  As a conventional penetration test method created in view of the above problems, there is one disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2007-321385). This penetration test method applies a plurality of different loads to the penetration rod in units of a predetermined depth, and acts on the rod with the resultant force Wa of the vertical circumferential friction Wf acting on the rod and the load W loaded on the screw point. To obtain the resultant force Ta between the horizontal circumferential surface friction Tf and the rotational load torque T of the screw point, determine the relationship between these resultant forces Wa and Ta, and compare this with the judgment criteria obtained in advance for various soil types. The soil quality is judged. As a result, in the penetration test to obtain the test data by penetrating the rod etc. into the ground by load and rotation like the conventional Swedish sounding test, both the load and rotation test data are related, and these The soil quality can be judged by comprehensively evaluating the soil quality. For this reason, the concept of the conventional self-sinking ground (the ground evaluated by Wsw) and the rotation penetrating ground (the ground evaluated by Nsw) is eliminated, the data processing after the test can be simplified, and the test results can be improved in the future. There is an advantage that problems in analysis and advanced use can be solved.

JP 2007-321385 A

Japanese Industrial Standard A1221 Swedish Sounding Test Method

  However, in the above penetration test method, the peripheral surface friction Wf and Tf should originally be values that only act on the rod, but due to the influence of the earth and sand adhering to the peripheral surface of the screw point, There was a problem of acquiring values including surface friction. In particular, in the clay layer, earth and sand adhere to the peripheral surface of the screw point and rotate integrally, so that such a problem has occurred remarkably.

The present invention has been made in view of the above problems, and allows the penetrating rod to rotate and penetrate while gradually changing the load W applied to the penetrating rod composed of the rod and a screw point connected to the tip of the rod. Measure the rotational torque T of the penetrating rod every time the predetermined depth is reached, measure the rotational torque Tm of the penetrating rod raised several centimeters every time the predetermined depth is reached, and act on the rod based on the rotational torque Tm. The maximum shear stress τmax is calculated, the maximum shear stress τmax is decomposed into a vertical component τz and a horizontal component τθ, and the peripheral friction vertical acting on the rod based on the vertical component τz and the horizontal component τθ of the maximum shear stress τmax is calculated. The component Wf and the horizontal component Tf are obtained, and the peripheral surface friction Wf and Tf are set as the loss values due to the peripheral surface friction of the rod. By correcting the click T, and obtains the load Wa and the rotating torque Ta acting on the screw points.

Further, by assuming that the maximum shear stress τmax and the combined speed ν of the rotation speed and settlement speed of the rod act in the same direction, the vertical component τz and the horizontal component τθ of the maximum shear stress τmax can be calculated. preferable.

  According to the present invention, the peripheral friction acting on the rod is calculated based on the rotational torque when the penetrating rod is pulled up and rotated once. As a result, the earth and sand adhering to the circumferential surface of the screw point is removed during the pulling up, and the earth and sand are not adhered to the circumferential surface of the screw point during rotation, and only the circumferential friction acting on the rod is calculated. Can do. Therefore, if the peripheral friction of the rod is removed from the load when the penetrating rod penetrates into the ground and the rotational load torque at the time of rotation, the load and the rotational load torque acting only on the screw point can be obtained. Test data reliability is improved.

  Further, the resultant force Wa of the vertical circumferential friction Wf acting on the rod and the load W applied to the screw point, and the resultant force of the horizontal circumferential friction Tf acting on the rod and the rotational load torque T of the screw point. Obtaining Ta, obtaining the relationship between these resultant forces Wa and Ta, comparing this with the judgment criteria obtained in advance for various soils, and judging the soil, so as to reliably consider the surface friction of the rod Judgment can be made.

It is a perspective view of the automatic penetration testing machine which enforces the penetration testing method concerning the present invention. It is an expanded side view of the automatic penetration testing machine which enforces the penetration testing method concerning the present invention. It is an expanded sectional view concerning the AA line of FIG. It is a principal part expanded partial notch sectional view of the automatic penetration test machine which implements the penetration test method which concerns on this invention. It is a graph which shows the rotational load torque on each condition. It is a graph for explanation about the experimental data for obtaining the judgment standard of soil quality. It is a graph for explanation about the experimental data for obtaining the judgment standard of soil quality. It is a graph for explanation about the experimental data for obtaining the judgment standard of soil quality. It is a schematic explanatory drawing of the experimental apparatus for obtaining the judgment criteria of soil quality. It is a graph which shows an example of soil quality criteria. It is a graph which shows another example of soil quality criteria. It is a conceptual diagram for the description of the circumferential friction which acts on the penetration rod penetrated into the ground.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.
In FIG. 1 to FIG. 4, reference numeral 1 denotes an automatic penetration testing machine, which has a lifting platform 3 that can be lifted and lowered along a standing column 2. The lift 3 includes a penetrating rod 4 connected to the tip of a rod-like rod 4a and a tip connected to the tip, a chuck unit 5 capable of holding the penetrating rod 4 integrally, and the chuck unit 5 A chuck motor 6 that rotates, a sprocket 7 that meshes with a chain member 2 a that extends in the longitudinal direction of the support column 2, a lift motor 8 that rotates the sprocket 7, and the sprocket 7 is rotated. Brake means 9 for braking and weights 3a for adjusting the mass are provided. When the total mass of the mass of these equipments and the mass of the lifting platform 3 is loaded on the penetrating rod 4, a load of 1 KN at maximum is applied to the penetrating rod 4. The chuck motor 6, lift motor 8 and brake means 9 are driven and controlled by a control unit 10.

  The chuck unit 5 is rotatably disposed on the lifting platform 3. Sprockets 11 and 12 are integrally fixed to the lower portion of the chuck unit 5 and the output shaft 6a of the chuck motor 6, respectively, and both are connected by winding an annular chain 13 around them. A proximity sensor (not shown) is provided at a position facing the teeth of the sprocket 11 on the chuck unit 5 side to detect the passage of the teeth when the sprocket 11 rotates and turn it on / off. The signal of the proximity sensor is acquired by the control unit 10, and the control unit 10 is configured to determine the half rotation number of the penetrating rod 4 from this signal.

  The sprocket 7 is connected to the elevating motor 8 via the one-way clutch 14 and the brake means 9, and the one-way clutch 14 moves up and down to rotate the sprocket 7 in the direction to raise the elevator 3. When the motor 8 is driven, this is transmitted to the sprocket 7. Driving the lifting motor 8 that rotates the sprocket 7 in the reverse direction (hereinafter referred to as reverse driving) causes the one-way clutch 14 to run idle. For this reason, when the lifting / lowering motor 8 is reversely driven while the screw point 4b is in contact with the ground, the penetrating rod 4 (rod 4a or screw point 4b) is loaded with a load such as the lifting platform 3 or the like. This load can be freely changed from 0 N to a maximum load of 1 KN by changing the force with which the brake means 9 brakes the sprocket 7. The brake means 9 is preferably a powder brake or a powder clutch.

  In the automatic penetration testing machine 1, the penetration test is started from the position where the screw point 4b at the tip of the penetration rod 4 is in contact with the ground surface. Up to this position, the manual operation button provided in the control unit 10 is pushed to reversely drive the lifting motor 8 to lower the lifting platform 3. When a test start signal is given by pressing the start button from this position, the control unit 10 automatically starts penetrating control of the penetrating rod 4 into the ground. That is, the control unit 10 receives the test start signal and reversely drives the lifting motor 8 and rotates the chuck motor 6. Thereby, the load by the mass of the lifting platform 3 etc. is loaded to the penetration rod 4, and it penetrates into the ground, rotating these.

  During the test, the control unit 10 determines the half speed of the penetrating rod 4. Further, the brake means 9 is controlled to increase the load applied to the penetrating rod 4 from the minimum load 200N in increments of 200N to the maximum load 1KN in a short time. . And the rotational load torque concerning the penetration rod 4 under each load is acquired. Since the rotational load torque applied to the penetrating rod 4 is proportional to the current value applied to the chuck motor 6, the rotational load torque is obtained from the load current value of the chuck motor 6 in this example. Further, the control unit 10 calculates the number of rotations of the sprocket 7 from the signal of the rotary encoder 15 that detects the rotation of the sprocket 7, calculates the penetration depth of the screw point 4b from this, and calculates the screw point 4b from the penetration depth per unit time. Determine the penetration speed. The change in load for each section, the rotational load torque under each load, and the half-rotation speed in each section are automatically stored in the control unit 10 as test data while the penetration depth increases by 25 cm as one section. . Thereby, different loads can be applied to the penetrating rod 4 in predetermined depth units, and a plurality of rotational load torques for each load can be acquired. Further, every time 25 cm penetrates, the penetrating rod 4 is lifted 1 cm and rotated once, and torque (Trm) is measured. This torque (Trm) is used when calculating the circumferential friction of the rod 4a, the details of which will be described later. For example, when the load change of 200 N to 1 KN is performed for 5 cycles while the penetration rod 4 penetrates 25 cm, 5 rotational load torques corresponding to each load are acquired in a total of 25. The control unit 10 repeats the above process to penetrate the screw point 4b to a predetermined depth (for example, a depth of 10 m in the ground). During the penetration test, the rod 4a of the penetration rod 4 is extended by screwing an extension rod (not shown) to the upper threaded portion 4c as necessary.

  The automatic penetration testing machine 1 processes test data by applying a plasticity analogy model to the rotational load torque corresponding to the aforementioned load. The plasticity analogy model is a mathematical model that describes the relationship between the load and displacement of a structure, using the same framework (analogue) as the constitutive law that gives the relationship between soil stress and strain. The load applied to the structure includes a vertical load, a moment, a horizontal load, etc., but the load at the time of destruction of the structure changes depending on the combination of other loads. In the plasticity analogy model, the magnitude of such a combined load is described as a yield surface, and the displacement increment corresponding to each of these loads is described using a plastic potential function. The test that penetrates the penetrating rod into the ground by applying load and rotation, such as the Swedish sounding test and the penetration test introduced in this example, applies the rotational load torque in the rotation stage in addition to the vertical load in the load stage. Since it is a load test, it can be said that it is one of the problems of combined loads to which the plasticity analogy model can be applied.

と表すことができる。ここでδｎｈｔは半回転数の増分、δｓｔは貫入量の増分である。数１を自沈荷重Ｗｐとスクリューポイントの最大直径Ｄとの積を用いて正規化すると、

となる。ここでＴｎは正規化トルク、Ｗｎは正規化荷重である。また、数２の結果から後述する塑性ポテンシャルの適用においては、ＴｎとδｎｈｔおよびＷｎとδｓｔ／Ｄがそれぞれ同軸性を有するものと判断している。
後述する実験結果から、貫入試験で得られる回転負荷トルクと荷重による降伏曲面は、原点に中心を有する楕円で表記できることが確かめられている。そこで、この降伏曲面の形状を決定する降伏曲面係数ｃｙを用いて、

と表す。この数３を数２を用いて表すと、

が得られ、これを整理すると、降伏曲面は次のような別形式で表すことができる。

塑性ポテンシャル関数についても降伏曲面と同様な楕円形状を有するものと仮定すると、

と表せる。ここでｃｐは塑性ポテンシャル係数であり、これが前記ｃｙに等しい時には関連流れ則が成立する。数５を微分することにより塑性ポテンシャル関数に直交する方向を求めると、

となる。ここで１ｍ貫入量当りの半回転数Ｎｓｗにスクリューポイント最大径Ｄを乗じたＮｓｗＤを正規化Ｎｓｗと定義する。 Therefore, the plasticity analogy model for such penetration tests is constructed as follows. First, the work increment δE due to the load W at the load stage and the rotational load torque T at the rotation stage applied to the screw point is:

It can be expressed as. Here, δnht is an increase in half rotation speed, and δst is an increase in penetration amount. When Formula 1 is normalized using the product of the self-sinking load Wp and the maximum diameter D of the screw point,

It becomes. Here, Tn is a normalized torque, and Wn is a normalized load. From the result of Equation 2, it is determined that Tn and δnht and Wn and δst / D have coaxiality in the application of the plastic potential described later.
From the experimental results to be described later, it is confirmed that the rotational load torque obtained by the penetration test and the yield curved surface by the load can be expressed by an ellipse having a center at the origin. Therefore, using the yield surface coefficient cy that determines the shape of the yield surface,

It expresses. When this number 3 is expressed using the number 2,

If this is arranged, the yield surface can be expressed in another form as follows.

Assuming that the plastic potential function has an elliptical shape similar to the yield surface,

It can be expressed. Here, cp is a plastic potential coefficient, and when this is equal to cy, the related flow law is established. When the direction orthogonal to the plastic potential function is obtained by differentiating Equation 5,

It becomes. Here, NswD obtained by multiplying the half rotation speed Nsw per 1 m penetration amount by the screw point maximum diameter D is defined as normalized Nsw.

  FIG. 5 shows the displacement of the rotational load torque for each depth under each condition (A, B, C). A is a graph showing the rotational load torque acting on the screw point 4b when the penetration rod is rotationally penetrated into the ground not drilled. The rotational load torque acting on the screw point 4b is the rotation of the penetration rod 4. The calculation is performed by removing the peripheral friction of the rod 4a detected by lifting the penetrating rod 4 from the load torque. B is also a graph showing the rotational load torque acting on the screw point 4b when the penetration rod 4 is rotationally penetrated into the ground not drilled, and the rotational load torque acting on the screw point 4b is the same as that of the penetration rod 4. It is calculated by removing the circumferential friction of the rod 4a detected without lifting the penetrating rod 4 from the rotational load torque. On the other hand, C indicates the displacement of the rotational load torque of the penetrating rod 4 when the penetrating rod 4 rotates and penetrates into a drilling hole that is smaller than the maximum diameter of the screw point 4b and larger than the diameter of the rod. . Accordingly, C rotates and penetrates without any resistance around the penetrating rod 4, so that the rotational load torque of the penetrating rod 4 can be regarded as the rotational load torque of the screw point 4b. Comparing these A, B, and C, it can be confirmed that A is closer to the value of C, that is, the peripheral surface resistance of the rod 4a is reliably removed.

  FIG. 6 to FIG. 8 show analysis results of experiments performed on clay soil samples. The experiment was conducted with an experimental artificial soil layer made of clay. The experimental artificial soil layer is Fujinomori Clay C, in which sand and gravel are spread as a drainage layer at the bottom of a circular soil tank B with a diameter of 28 cm and a height of 50 cm shown in FIG. 9, and the water content ratio is adjusted to 50% from above. In order to increase the water permeability of this clay C, it is deaerated using a vacuum pump for 24 hours, and then, about 20 kPa is loaded stepwise from the upper part and the lower part is decompressed to -100 kPa to perform consolidation. Obtained.

  As shown in FIG. 9, the experimental apparatus includes a rod 20, a weight 21, a weight loading device 22 with a bearing, a screw point 23, and a torque meter 24. Here, the screw point 23 is made of silver clay so as to be 1/5 of the actual size, and has a shape in which a square weight is twisted once to the right and has a maximum diameter of 6.7 mm and a long length. The length is 40 mm.

  In the experiment method, first, the screw point 23 and the weight loading device 22 are attached to the tip of the rod 20, and the rod 20 is fixed so as to penetrate vertically. Next, the initial weight 21 is loaded, and the amount of penetration at that time is measured after self-sink (penetration only by load) stops. On the other hand, if the self-sink does not settle even when the maximum load is loaded, the torque gauge 24 is used for rotational penetration. The screw point 23 penetrates to a depth of 25 cm while obtaining a self-sinking load or rotational load torque every 5 cm by this method. When the screw point 23 penetrates to a depth of 25 cm, the test is repeated in a similar manner withdrawing once and changing the maximum load. This is performed by changing the maximum load in five stages of 40N, 80N, 120N, 160N, and 200N, for example, so that a self-sinking load at the same depth (every 5 cm) or a rotational load torque with different loads can be obtained. FIG. 6 is a plot of these (πT / D) 2 and W 2 relationships for each depth. The slope in FIG. 6 is the yield surface coefficient cy, and the X-axis intercept is the self-sink load Wp. FIG. 7 plots the relationship between πT / WpD and W / Wp by substituting the self-sinking load Wp, the maximum load W, and the rotational load torque T at each depth obtained in this way into Equation 4, and in FIG. The solid line indicates the theoretical value calculated by substituting the yield surface coefficient cy into Equation 4. Comparing the theoretical value with the experimental value, although there was some variation, the existence of an elliptical yield surface like the theoretical value was confirmed. FIG. 8 is a graph showing the relationship between the normalized Nsw in Equation 7 and πT / WD using the load W and the rotational load torque T obtained for the clay ground.

  FIG. 10 shows an experiment using an experimental artificial soil layer prepared for each soil sample of Kanto Loam, medium-density sand, and dense sand in the same manner as the clay ground described above. It is the figure plotted on the same scale with the ground one. Thereby, it turns out that a yield surface shows a different shape in each soil. In this way, it is possible to determine the soil quality by comparing the yield curved surface obtained for each soil with the yield curved surface obtained in the test on the actual ground (hereinafter referred to as actual ground). Is possible. It should be noted that the yield surface is not limited to an ellipse, and is considered to have various shapes depending on the soil quality. For this reason, it is preferable to prepare as many types of yield curved surfaces for each soil as the soil determination criteria by experiments with various soil samples or actual measurements on the actual ground.

FIG. 11 shows the relationship between the normalized Nsw in Equation 7 obtained from the experimental results of Kanto Loam, medium sand, and dense sand and πT / WD together with those of the clay ground on the same scale. . Also in this relationship, since different slopes are shown for each soil, that is, the plastic potential coefficient cp, this graph can also be used as a soil judgment criterion. Table 1 below summarizes the yield surface coefficient cy and the plastic potential coefficient cp for clay, Kanto loam, medium density sand, and dense sand obtained from the above experimental results. It can be seen that these values also differ depending on the soil quality. For this reason, the load W and the rotational load torque T are acquired by the penetration test in the actual ground, and the coefficients cy and cp are obtained from the above equations 3 to 7 using the reference values obtained in advance through experiments. It is also possible to determine the soil quality by comparing.

また、ロッド４ａに作用する周面摩擦Ｗｆ，Ｔｆを算出するには、２５ｃｍ貫入する毎に貫入ロッド４を１ｃｍ引き上げて、その最の回転トルクＴｒｍを計測する。このときの最大せん断力は、次式で表される。

さらに、合速度方向と合せん断応力の方向が等しいと仮定すると数１１および数１２が得られる。

ここで、δｎｈｔは回転数、δｓｔは貫入量、ｒはロッド径、τは合せん断応力、τθは水平方向のせん断応力、τｚは鉛直方向のせん断応力である。
一方、回転および自沈貫入により生じる摩擦をそれぞれＴｆ，Ｗｆとすると、数１３が得られる。

この数１３より、

が得られ、続いて、この数式１４より、

が得られ、数１２，１３および数１４から、

となる。ここで、Ｆは荷重およびトルクによる周面摩擦Ｗｆ，Ｔｆの合力である。数７、数８および数１５より、

また、数９および数１７より、

となり、この数１８をＮｓｗＤについて解くと、

となる。この数１９により、ロッド４ａの周面摩擦を考慮した正規化Ｎｓｗを得ることができる。正規化Ｎｓｗを土質判定の基準として用いる場合には、この周面摩擦を考慮した正規化Ｎｓｗを用いるのがよい。また、上述の降伏曲面を求める場合にも、スクリューポイント４ｂに作用している荷重Ｗと回転負荷トルクＴを用いた方がよい。この場合には、特開2001-228068号公報によって示される方式により、スクリューポイント４ｂにかかる荷重Ｗを求めることができる。さらに、前述した貫入ロッド４を１ｃｍ引き上げて計測したロッド４ａの水平面周面摩擦Ｔｆと実測された回転負荷トルクＴａとを数８に代入すればスクリューポイント４ｂに作用する回転負荷トルクＴを求めることができる。このようにしてロッド４ａに作用する周面摩擦による荷重やトルクを除外したスクリューポイント４ｂに本来作用している荷重Ｗと回転負荷トルクＴを求め、これらを用いることにより、より正確な降伏曲面を求めることができる。 In the penetration test in the actual ground, when the penetration rod 4 penetrates into the ground, the length of the rod 4a is increased, and thus the resistance of the soil acting on the rod 4a is increased. Therefore, when the analysis based on the plasticity analogy model described above is applied to an actual penetration test, it is necessary to consider the influence of the peripheral friction acting on the rod 4a. FIG. 12 shows a conceptual diagram of the peripheral friction acting on the penetrating rod 4. When the circumferential friction in the vertical direction acting on the rod 4a is Wf, the torque due to the horizontal circumferential friction is Tf, the load applied to the screw point 4b is W, and the rotational load torque is T, the circumferential friction is The considered load Wa and the rotational load torque Ta (the load actually applied to the penetrating rod 4 and the detected rotational load torque) are expressed by Equations 8 and 9.

Further, in order to calculate the circumferential friction Wf and Tf acting on the rod 4a, the penetrating rod 4 is pulled up by 1 cm every time 25 cm penetrates, and the maximum rotational torque Trm is measured. The maximum shear force at this time is expressed by the following equation.

Further, assuming that the resultant velocity direction and the resultant shear stress direction are equal, Equations 11 and 12 are obtained.

Here, δnht is the rotational speed, δst is the penetration amount, r is the rod diameter, τ is the combined shear stress, τθ is the horizontal shear stress, and τz is the vertical shear stress.
On the other hand, if the friction caused by rotation and self-sinking is Tf and Wf, respectively, Equation 13 is obtained.

From this number 13,

Then, from Equation 14,

Is obtained from Equations 12, 13, and 14.

It becomes. Here, F is the resultant force of the circumferential friction Wf and Tf due to the load and torque. From Equation 7, Equation 8, and Equation 15,

From Equation 9 and Equation 17,

And solving this number 18 for NswD,

It becomes. By this equation 19, it is possible to obtain a normalized Nsw in consideration of the peripheral surface friction of the rod 4a. When using the normalized Nsw as a reference for determining soil quality, it is preferable to use the normalized Nsw in consideration of this peripheral surface friction. Also, when obtaining the above-mentioned yield surface, it is better to use the load W and the rotational load torque T acting on the screw point 4b. In this case, the load W applied to the screw point 4b can be obtained by the method disclosed in Japanese Patent Laid-Open No. 2001-228068. Furthermore, the rotational load torque T acting on the screw point 4b can be obtained by substituting the horizontal rotational surface friction Tf of the rod 4a measured by lifting the penetrating rod 4 1cm and the measured rotational load torque Ta into the equation (8). Can do. In this way, the load W and the rotational load torque T acting on the screw point 4b excluding the load and torque due to the circumferential friction acting on the rod 4a are obtained, and by using these, a more accurate yield surface is obtained. Can be sought.

  The load and the rotational load torque obtained as test data in the penetration test by the automatic penetration tester 1 correspond to the load Wa and the rotational load torque Ta. Therefore, in the processing of the test data, the control unit 10 first calculates the penetration rod for each penetration depth of 25 cm from each load Wa applied to the penetration rod 4 in the penetration depth of 25 cm and the corresponding rotational load torque Ta. The influence of the circumferential friction of the rod 4a calculated based on the torque Trm when the 4 is pulled up by 1 cm and rotated once is excluded, and the load W and the rotational load torque T applied to the screw point 4b are obtained. Then, using these, the yield surface coefficient cy and the self-sinking load Wp are obtained using Equation 5. When the control unit 10 constantly monitors the penetration speed of the penetration rod 4 and determines that self-settlement has occurred while increasing the load, the control unit 10 maintains the load and continues to penetrate to a separation depth of 25 cm. The load causing the self-sink is defined as self-sink load Wp.

  The control unit 10 substitutes the self-sink load Wp obtained as described above, each load value W as test data, and the rotational load torque T corresponding to each load value into Equation 4, and πT / WpD, W / While calculating Wp, the theoretical value is calculated by substituting the yield surface coefficient cy into Equation 4. Then, a yield curved surface in which these πT / WpD, W / Wp and theoretical values are plotted is created, and this is displayed and output on the liquid crystal panel 10a or printed on the printer 10b so that the operator can visually recognize it. . The operator can determine the soil quality by comparing the output yield surface graph with the shape of the reference yield surface graph for each soil obtained by the above-described experiment or the like. Thus, by obtaining the yield curved surface of each section (every penetration depth 25 cm), it is possible to obtain a unified analysis result of the load and the rotational load torque over the entire depth of penetration of the screw point 4b. In addition, since it is possible to determine the soil quality in each section by comparing the graph shapes, even a person who does not necessarily have sufficient empirical techniques and abilities can perform accurate soil quality determination. This also means that, for example, owners of private houses who do not have sufficient knowledge in ground surveys can more easily grasp soil quality and ground strength from the analysis results.

  In the above description, the load applied to the penetrating rod 4 is changed stepwise to obtain the rotational load torque under each load every time the screw point 4b penetrates 25 cm. The rotational load torque for different loads at each predetermined depth may be acquired by the following method. That is, while penetrating the rod at a predetermined depth (for example, 25 cm), the penetrating rod 4 is penetrated into the ground by appropriately performing self-sinking and rotating penetration according to a normal Swedish sounding test method. Then, every time the screw point 4b penetrates to a predetermined depth, the load is once set to 0 (zero), and from here, the load is increased to 200N, 400N, 600N, 800N, 1KN (however, when the self penetration has occurred while penetrating the predetermined depth) Increases the maximum load at which self-sinking occurs, and rotates the penetration rod 4 for each load to obtain a rotational load torque. The relationship diagram of the above-described yield surface and normalized Nsw can be obtained also by the load obtained by this and the rotational load torque corresponding to each load.

  Further, the control unit 10 may be configured to create a graph showing the relationship between the normalized Nsw and πT / WD from the obtained test data and to output the graph so that the operator can see it. As in the case of using the yield surface described above, it is possible to obtain a unified analysis result by load and rotational load torque over the entire depth of penetration of the screw point 4b, as well as interpretation of soil judgment and test results. Can relax their expertise. Furthermore, each load Wa of the penetration depth of 25 cm unit of the screw point 4b and the rotational load torque Ta detected corresponding thereto are regarded as the load W and the rotational load torque T applied to the screw point 4b, and the test data Processing may be performed.

DESCRIPTION OF SYMBOLS 1 Automatic penetration test machine 2 Support | pillar 2a Chain member 3 Lifting stand 4 Penetrating rod 4a Rod 4b Screw point 5 Chuck unit 6 Chuck motor 7 Sprocket 8 Lifting motor 9 Brake means 10 Control unit

Claims (2)

The penetrating rod is rotationally penetrating while gradually changing the load W applied to the penetrating rod composed of the rod and a screw point connected to the tip of the rod, and the rotational torque T of the penetrating rod is measured every time a predetermined depth is reached. And measuring the rotational torque Tm in a state where the penetration rod is pulled up several centimeters every time the predetermined depth is reached,
Calculating the maximum shear stress τmax acting on the rod based on the rotational torque Tm;
Decomposing the maximum shear stress τmax into a vertical component τz and a horizontal component τθ,
Based on the vertical component τz and horizontal component τθ of the maximum shear stress τmax, the vertical component Wf and the horizontal component Tf of the circumferential friction acting on the rod are obtained,
The load Wa and the rotation torque Ta acting on the screw point are obtained by correcting the load W and the rotation torque T of the penetrating rod with the peripheral surface friction Wf and Tf as loss values due to the surface friction of the rod. Penetration test method. The vertical component τz and the horizontal component τθ of the maximum shear stress τmax are calculated by assuming that the maximum shear stress τmax and the combined speed ν of the rotation speed and settlement speed of the rod act in the same direction. The penetration test method according to claim 1.

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