JPH03505108A - Soil test method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Soil test method Technical field The present invention relates to engineering geological surveys carried out in conjunction with construction projects, and particularly to soil testing methods. Regarding.

Background technology In civil and industrial engineering, high-rise buildings, nuclear power plant reactors, hydroelectric power plants It is common practice to conduct soil tests on land where important structures such as large industrial facilities are constructed. required. The supporting ground has a grain size of 2 mm or more (for example, crushed rock or wood ) The possibility of containing more than 50% non-cementous clastic rock cannot be excluded. gravel, Coarse sand, fine sand, sandy loam, argillaceous clay, etc. are also frequently encountered. solidification This test is necessary to determine the pressure, bulk modulus of the soil, settlement rate of the structure, etc. Become. Even the slightest error in these measurements can lead to structural defects or unreasonable project output. High precision is required as it leads to costs.

Conventional soil testing methods (soil: method for determining stress-strain properties in the field, USSR standard) Semi-GO3T20276-85゜p20) is to dig a vertical shaft into the soil layer to be investigated. The process of preparing the test site by and having a surface area of approximately 5000 cd at the site. The process of installing a slab and applying incremental static loads to the slab The method consists of a step of measuring the amount of subsidence of the slab corresponding to the load. solidification Pressure, soil bulk modulus, and settlement rate are calculated from this test data.

However, the above conventional method cannot be used at the test site for deep layers of soil with high moisture content. This cannot be applied because it may become flooded and difficult to access. Water inundation may cause soil content. Increase the water rate and affect its physical and mechanical properties before applying static loads I don't like that fact. Due to the high moisture content of the soil, the slab is It will not be possible to contact the soil layer uniformly and the results obtained will be inaccurate. becomes. Installing a slab under these conditions and subjecting it to a static load will prevent its settling. Measuring decline is difficult.

The traditional method is to reduce the deformation caused by the lateral pressure of the soil mass above the site after excavating the pit. Since its strength is impaired by . Overall, another method of soil testing (Soil: Determination of stress-strain properties in situ) Method, USSR Standard GO3T20276-85, pp5-6.2O-21) was opened. It is being emitted. According to this, the soil layer above the tested layer is attached to the lower end of the main shaft. Deformed by a spiral cutting blade that is attached and screwed into the soil to a predetermined depth. It will be done. After screwing is completed, a series of static loads are applied axially downward to the spindle. , so that each successive load exceeds the preceding load by the same amount, and each load The displacement of the main axis is measured.

With this method, there is no need to install special equipment within the soil layer to be tested. No flooding or weakening occurs, making it possible to test deep layers with high moisture content or deep layers of soft soil. can.

However, as the cutting blade descends while scraping the soil layer in front of it, The layer under test deforms before being subjected to static loads. As a result, the accuracy of test data This will lead to loss of reliability. Furthermore, if part of the surface of the lower end of the cutting blade is the layer to be tested. Since the cutting blade may move away from the When descending with Uniform contact cannot be obtained. This condition may cause the spindle and cutting blade to penetrate into the soil. The sum of the opposing forces is slightly greater than the sum of the forces applied to make this penetration. Occurs at different times. As a force against the above penetration, the soil is at the tip of the descending main shaft. the resistance force exerted, the frictional force exerted by the play between the soil and the descending spindle, and the cutting blade This includes the vertically upward component of the resistance force exerted by the soil on the cutting edge. Above spindle The forces applied to the There is a traction force from the spiral cutting blade.

Disclosure of invention The main purpose of the present invention is to obtain test data with high accuracy and reliability. The purpose of the present invention is to provide a soil test method, which involves the lower surface of the cutting blade and the soil layer being tested. This can be achieved by preventing deformation of the layer under test under uniform contact conditions between the layers.

To achieve this purpose, A spindle with a spiral cutting blade attached to the lower end deforms the soil layer above the layer being tested. A soil test method that involves screwing into the soil so as to stopping the screwing operation when the cutting blade reaches a depth at which the layer to be tested appears; A series of static loads are applied axially downwards to the main shaft, thereby causing each subsequent A process in which a load exceeds a preceding load by the same amount; a step of measuring the displacement of the main shaft corresponding to the load, the amount by which the pressure exerted by the soil on the lower surface of said cutting blade exceeds the pitch of the cutting blade; The original state of the soil above the cutting blade when measured at a soil location shallower than the location of the tested layer. If the pressure is different from the soil column pressure, the axial load is applied to bring each load to a common level. Applied to the cutting blade via the main shaft, Discloses a soil testing method characterized by the following.

The soil pressure on the lower surface of the cutting blade should be equal to the pressure of the original soil column above the cutting blade. As a result, the deformation of the soil due to the descending cutting blade is transferred from the layer in front of the cutting blade to the layer above it. It is "transferred" to the other layer. Prevents deformation of the layer under test before static loads are applied Therefore, this "transfer" improves the accuracy and reliability of the test data.

The pressure supported by the lower surface of the cutting blade means contact between this surface and the soil. , the lower surface of the cutting blade is spiral-shaped to ensure uniformity of contact, and the test further guarantees the accuracy and reliability of

Brief description of the drawing Figure 1 shows the main shaft with a spiral cutting blade in the position before conducting a clay soil test; Figure 2 is a diagram showing the main parts of the main shaft with a spiral cutting blade in Figure 1; Figure 3 shows that the position of the cutting blade is shallower than the position of the tested layer by the amount that exceeds the pitch of the cutting blade. Diagram showing the spindle with cutting blade in position, Figure 4 is a diagram showing the main shaft with the cutting blade when the cutting blade is at the position of the layer to be tested; Figure 5 shows the spindle with a helical cutting blade in its position before conducting a soil test on dense fine sand. figure, Figure 6 shows the main parts of the spindle with a spiral cutting blade, and Figure 7 shows the position of the cutting blade under test. When the main body with a cutting blade is located at a shallower position than the position of the cutting layer by an amount exceeding the pitch of the cutting blade. Diagram showing the axes, FIG. 8 is a view showing the main shaft with a cutting blade when the cutting blade is located at the layer to be tested.

Best mode for carrying out the invention In the soil testing method according to the present invention, the main shaft has a spiral cutting blade at the lower end. It is screwed into the soil in such a way as to deform the layer above the soil layer under test. tested When the depth is shallower than the depth of the test soil layer by the pitch of the cutting blade, the cutting The pressure of the soil on the lower surface of the cutting blade is measured. If this pressure is above the cutting edge is different from the pressure of the original soil column, the load in the main axis direction that equalizes the two pressures is the main one. Applied to the cutting blade via the shaft. Screws in when the cutting blade reaches the depth of the soil layer to be tested The grinding operation is stopped and a series of downward axial loads are applied, each exceeding the preceding load by the same amount. A static load is applied to the spindle and the displacement of the spindle in response to the load is measured. disclosed The invention is applied, for example, to testing soil properties such as clay. Referring to Figure 1, a certain building If a building is built with a foundation that is 20 m wide, the depth L is generally equal to the width of the foundation. The test is carried out on layer 1 of soil 2 which appears at l, ie L1=20 m. this layer 1 is schematically defined by the dashed line in FIG. The main shaft 3 used for testing has a length L 2 = 23 m, diameter dl' = 11.4 cm (Figure 2), and diameter DI = 27.7 cm, and a spiral cutting blade 4 with a pitch tl = 8 an.

The pressure PI of the original soil column of the soil 2 above the cutting blade 4 (Fig. 1) is 0 at depth. It is 4MPa.

The main shaft 3 is installed perpendicularly to the surface 5 of the soil 2, with the cutting blade 2 facing downward. by applying a torque of 0.5 tm and a downward axial force of P2=1t. It is screwed into the soil layer 6 above the test layer 1 and deforms the soil layer 6.

The soil layer 2 in which the tested layer l appears by an amount L4 larger than the pitch t1 of the cutting blade 4 At the position of depth L3 (Figure 3) of soil 2, which is shallower than depth Ll of The pressure of the soil 2 on the surface 7 is measured. This pressure is applied to the soil 2 above the cutting blade 4. When the pressure P1 of the original soil column is different, the pressure is adjusted through the main axis so that the pressure P1 and P2 are equal. As a result, an axial pressure P4 is applied to the cutting blade 4. Ll = 20m, tl = 8a n, the measurement of pressure P3 is started from, for example, L3 = 18.5 m, and P3 = 0 ．． Assume that 48 MPa is obtained. In this case, the pressure applied to the lower surface 7 of the cutting blade is The pressure exceeds the pressure P1 of the original soil column of the soil 2 above the cutting blade 4. Pressure P3 is 0.4 MPa An upward axial force P4 is applied to the cutting blade 4 via the main shaft 3 in order to It will be done. While maintaining Pl and P3 at a common level, the main shaft 3 has a cutting edge up to a depth of L + It is lowered together with 4. The screwing work is interrupted and each is preceded by the same amount. Continuous axial downward static loads P5, P6, P7 and P8 exceeding the load (Fig. 4) is applied to the main shaft 3. Displacement L5 of main shaft 3 corresponding to each load , L6, Ll, and L8 (not shown) were measured as follows.

When P5=0.1MPa, L5=1.8mm When P6=0.2MPa, L6= L when 11mmP7=0.3MPa? =2.0mmP8=0.4MPa L8=Z4mm Other properties such as bulk modulus and stress-strain properties of soil are based on these data. Calculated from data.

Another embodiment of the invention is for testing dense fine sand with a density of '2.1 g/cm3. It can be applied to In this case, a 10m wide foundation is required to construct the building. Ru. The depth L9 (Fig. 5) of the soil layer to be tested is therefore approximately 10 m. soil This layer 8 of 9 is defined schematically by a dashed line.

The test is conducted using a spindle 10 with a helical cutting edge 11 having the following dimensions.

Main shaft length L10=13m Main shaft diameter ci2 = 11.4an (Fig. 6) Cutting blade diameter D2 = 27.7a n Cutting blade pitch t2 = 50 The pressure P9 of the original soil column of the soil 9 above the cutting blade 11 is 0.21 MPa at the depth L9. be.

The main shaft 10 is installed perpendicularly to the surface 12 of the soil 9, with the cutting blade ]1 facing downward and M2 By applying a torque of =0.3 tm and a downward axial force of PiO = 0.75 t. screwed into the layer 13 of the soil 9 above the layer 8 to be tested, deforming the soil layer 13. Ru. At a depth of 1 m (not shown) the force PIQ is removed.

At a depth L11 = 8 m (Fig. 7), the pressure of the soil 9 on the lower surface 14 of the cutting blade II The power pH is measured to obtain 0.05 MPa. Depth Lll is L1 from depth LIO Note that it is shallow by 2 = 2 m. applied to the lower surface 14 of the cutting blade 11 Since the pressure pH is smaller than the pressure P9 of the original soil column above the cutting blade 11, the shaft A force P12 in the downward direction is applied to the cutting blade 11 via the main shaft 10, thereby causing pressure The force pH increases from 0.05 MPa to 0.21 MPa. Same pressure P9 and pH While maintaining the same level, the spindle 10 becomes integrated with the cutting blade 11, and the layer 9 to be tested appears. Can be screwed down to depth L9. Torque M9 is removed at this depth (Fig. 8). The screwing movement is stopped at , and each successive load exceeding the preceding load by the same amount Four downward loads P13, PI3, PI3, PI3 are applied to the main shaft 10. Ru. Displacements L13, Li2, L15, Li2 of the main shaft 10 according to each load (not shown) ) was measured as follows.

When P13=0.1MPa L13=0.9mm When P14=0.2MPa L 14=0.7mmP15=0.3MPa L15=0.9mmP16 When = 0.4 MPa, L16 = 1.0 mm Soil bulk modulus and its stress - Other properties such as distortion properties can be obtained from the above data.

Industrial applicability The present invention applies to important structures such as nuclear power plant reactors, hydroelectric power plants, large industrial facilities, etc. It is effective for testing the soil quality of the ground on which buildings are built.

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Claims (1)

[Claims] The main shaft (3, 10) with a spiral cutting blade (4, 11) attached to the lower end was placed under test. The soil is deformed so as to deform the layer (6, 13) of the soil (2, 9) above the layer (1, 8). A soil test method in which the cutting blade (4, 11) is screwed into the soil (2, 9), the cutting blade (4, 11) being When the depth (L1, L9) at which the tested layer (1, 8) appears is reached, the screwing operation is carried out. A process to be canceled; A static load (P5, P6, P7, P8, P13, P14, P15, P16) so that each subsequent load is the same. The process of exceeding the preceding load by the amount, Compatible with the above loads (P5, P6, P7, P8, P13, P14, P15, P16) The displacement of the main shaft (3, 10) (L5, L6, L7, L8, L13, L14, a step of measuring L15 and L16; Equipped with The soil (2, 9) is applied on the lower surface (7, 14) of the cutting blade (4, 11). The pressure (P3, P11) changes the pitch (t1, t2) of the cutting blades (4, 11). Soil (2) shallower than the position of the test layer (1, 8) by an amount exceeding (L4, L12) , 9), when measured at the positions (L3, L11), the upper part of the cutting blade (4, 11) If the pressure of the soil (2, 9) is different from the pressure of the original soil column (P1, P9), each negative To bring the loads (P1, P3, P9, P11) to a common level, the axial load (P4 , P12) is applied to the cutting blade (4, 11) via the main shaft (3, 10). A soil testing method characterized by the fact that