GB2488053A - Testing method and device for coefficient of subgrade reaction test - Google Patents
Testing method and device for coefficient of subgrade reaction test Download PDFInfo
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- GB2488053A GB2488053A GB1205190.0A GB201205190A GB2488053A GB 2488053 A GB2488053 A GB 2488053A GB 201205190 A GB201205190 A GB 201205190A GB 2488053 A GB2488053 A GB 2488053A
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- 238000012360 testing method Methods 0.000 title claims abstract description 199
- 238000006243 chemical reaction Methods 0.000 title claims description 49
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 54
- 239000002689 soil Substances 0.000 claims description 46
- 238000006073 displacement reaction Methods 0.000 claims description 25
- 238000007596 consolidation process Methods 0.000 claims description 20
- 230000005484 gravity Effects 0.000 claims description 19
- 239000007788 liquid Substances 0.000 claims description 11
- 238000012937 correction Methods 0.000 claims description 10
- 239000004816 latex Substances 0.000 claims description 10
- 229920000126 latex Polymers 0.000 claims description 10
- 238000005259 measurement Methods 0.000 claims description 10
- 239000010409 thin film Substances 0.000 claims description 10
- 238000004364 calculation method Methods 0.000 claims description 9
- 239000012153 distilled water Substances 0.000 claims description 5
- 239000000839 emulsion Substances 0.000 abstract 1
- 239000004927 clay Substances 0.000 description 53
- 108010066114 cabin-2 Proteins 0.000 description 35
- 238000004088 simulation Methods 0.000 description 25
- 238000000034 method Methods 0.000 description 13
- 238000012795 verification Methods 0.000 description 9
- 238000011065 in-situ storage Methods 0.000 description 7
- 239000004033 plastic Substances 0.000 description 6
- 239000011800 void material Substances 0.000 description 5
- 238000005070 sampling Methods 0.000 description 4
- 238000011835 investigation Methods 0.000 description 3
- 238000010561 standard procedure Methods 0.000 description 3
- 238000010276 construction Methods 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- 238000009628 steelmaking Methods 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000010835 comparative analysis Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000005527 soil sampling Methods 0.000 description 1
- 238000007655 standard test method Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 230000001131 transforming effect Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
- G01N3/10—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces generated by pneumatic or hydraulic pressure
- G01N3/12—Pressure testing
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D1/00—Investigation of foundation soil in situ
- E02D1/02—Investigation of foundation soil in situ before construction work
- E02D1/022—Investigation of foundation soil in situ before construction work by investigating mechanical properties of the soil
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Abstract
A testing device for foundation bed coefficient test comprises a pressure cabin (2); a cylindrical emulsion film (17) adhered in an inner cavity of the pressure cabin (2); a lower water-permeating plate (14), a sample (9) and an upper water-permeating plate assembly provided from bottom to top in sequence on a base seat of the inner cavity of the pressure cabin (2). An outer pressure plate (16) is connected with an upper water-permeating ring plate (15) of the upper water-permeating plate assembly. An inner pressure plate (21) is connected with an upper water-permeating inner plate (20). The outer pressure plate (16) is sleeved out of the inner pressure plate (21). A flange disk (22) is sleeved on a force transmitting sleeve of the outer pressure plate (16). The flange disk (22) and the pressure cabin (2) are connected by a bolt. A supporting bolt (23) on the flange disk (22) contacts with the outer pressure plate (16). There is a slot in the base seat of the pressure cabin (2), and a drainpipe (10) is provided in the slot. A three-way valve (24) is provided on the drainpipe (10). A pressure sensor (11) is connected with one end of the three-way valve (24), and a lower branch drain pipe (19) is connected with the other end of the three-way valve (24). The pressure sensor (11) is connected with a collector (12), and the collector (12) is connected with a computer control system. A hydraulic cavity volume adjusting cylinder (5) and a fully automatic hydraulic controller (6) of a side pressurizing device are connected to the inner cavity of the pressure cabin (2) respectively. A testing method for foundation bed coefficient test includes using the said testing device for foundation bed coefficient test to determine the foundation bed coefficient.
Description
Testing Method and Device for Coefficient of Subgrade Reaction Test
Technical Field
The invention relates to the technical field of rock and soil measurement, in particular to a testing method and device for coefficient of subgrade reaction test.
Background of the Invention
The coefficient of subgrade reaction is a key parameter of a Winkler foundation model. At present, the standard method for determining the coefficient of subgrade reaction adopts an in-situ 1(30 load test and there is no standard test method for determining the coefficient of subgrade reaction indoors. Only in the specification of Geotechnical Engineering Investigation of Underground Railway and Track Traffic', the method of using a triaxial test and a consolidation test to determine the coefficient of subgrade reaction is disclosed, but the specific test method standard and the evaluation method are absent, thereby causing many uncertain factors in actual operation and difficulty to implement. Through actual applications in Yangtze River tunnel, Tianjin subway and other projects, the measured values are different from the standard values by 5-10 times, the test boundary conditions of the two methods are greatly different from that of the (30 load test, and there is yet any answer to how the measured values are related with the 1(30 standard values.
The load test is the standard method for determining the coefficient of subgrade reaction of foundation soil and the foundation bearing capacity At present, there is no standard method for determining the coefficient of subgrade reaction indoors, and the foundation bearing capacity is also calculated by determining the physical and mechanical properties of the foundation soil, and there is no testing method and device for directly determining the bearing capacity Along with the rapid development of science and technology there are more and more building foundation pits, subways, tunnels and other projects, but the use of the load test to determine the coefficient of subgrade reaction is limited by many factors and therefore the adoption of the indoor test for rapid and accurate determination of the coefficient of subgrade reaction has great practical value and economical value.
Summary of the Invention
The invention aims at developing a testing instrument which is simple in structure and effective in practice and, in particular, a testing method and device for rapid and accurate determination of the coefficient of subgrade reaction.
A testing method for a coefficient of subgrade reaction test comprises the following steps: (1) Assembling a container according to requirements and filling up degassed distilled water into a hydraulic cavity volume adjusting cylinder; opening a water inlet valve, filling up degassed water into a pressure cabin and removing all bubbles; placing a standard correction test sample (I 100mm and h=lSOmm) into the container; exerting lateral pressure stage by stage by 100KPa/min up to 800KPa and keeping 800KYa pressure for 10 minutes on the premise of having no water leakage; and relieving the pressure and taking out the correction block; (2) Preparing a test sample (cb=95-lOOmm and h=120-lSOmm), keeping the two ends of the test sample leveled and sticking 15-18 filter paper strips (b=Smm) around the sample; and removing gas in the pipeline and loading the test sample according to the requirements; (3) Hoisting the hydraulic cavity volume adjusting cylinder so as to enable the liquid level to be 30-50cm higher than the top end of the test sample, to enable a cylindrical latex thin film to be in complete contact with the test sample and to generate contact pressure at about 3-5KPa, and to close the water inlet valve; (4) Applying full-section vertical load on an upper water-permeating plate component stage by stage up to gravity pressure of soil, wherein the gravity pressure of the soil is divided into 1-5 stages according to positions of soil samples; (5) Applying load for each stage for one hour, then commencing measuring and recording the hourly lateral pressure and lower-end water displacement; judging stability according as the difference between the water displacement in two hours is less than 0. lml or the residual value of bottom hole pressure is not more than 5% of the vertical pressure, and applying load for next stage; (6) Locking an outer pressure plate after the consolidation of the test sample is stable under the action of the gravity pressure and opening a full-automatic hydraulic controller to stabilize the lateral pressure of the test sample at the endpoint value during self-weight consolidation.
(7) Reliving the axial pressure, exerting the axial pressure on the test sample by a force transmitting column of a local section loading plate in 10-12 stages till breakage of the test sample; (8) Applying load for each stage by 1', 2', 5', 10', 30', lh, 2h, 3h, ... ; recording the axial deformation value under the corresponding load, and applying load for next stage if stability is confirmed when deformation increment per hour is less than 0.0 1mm, or if deformation is not greater than 0.1mm under measurement of deformation in 2-minute interval till the breakage of the test sample, and with the said method no fiher paper strip is pasted; (9) Drawing a P-S curve; (10) Determining the coefficient of subgrade reaction of foundation soil and the foundation bearing capacity according to characteristic points of the P-S curve.
When the deformation increment per hour is less than 0.1mm and the stability is confirmed, the slope of a regression straight line of all points before critical edge load is taken as the coefficient of subgrade reaction; By assuming the stability criteria as deformation no greater than 0.1mm under measurement of deformation in 2 minute interval, load for next stage is applied till the breakage of the test sample, the deformation under each stage of the pressure is to be amplified by six times and then the calculation is directly performed according to a formula of JC3 in the Specification.
A testing device for the coefficient of subgrade reaction test, comprising a pressure cabin 2, wherein a cylindrical latex thin film 17 is stuck in an inner cavity of the pressure cabin 2, a lower water-permeating plate 14, a test sample 9 and an upper water-permeating plate component are sequentially arranged on the base of the inner cavity of the pressure cabin 2 from bottom to top, an outer pressure plate 16 is connected on an upper water-permeating annular plate 15 of the upper water-permeating plate component, an inner pressure plate 21 is connected on an upper water-permeating inner plate 20, the outer pressure plate 16 is sheathed outside the inner pressure plate 21, a flange plate 22 is sheathed on the force transmitting sleeve of the outer pressure plate 16, the flange plate 22 is in bolted connection with the pressure cabin 2, and a support bolt 23 arranged on the flange plate 22 is in contact with the outer pressure plate 16; a slot is formed in the base of the pressure cabin 2, a water outlet pipe 10 is arranged in the slot, a three-way valve 24 is arranged on the water outlet pipe 10, one end of the three-way valve 24 is connected with a pressure sensor 11 through a pipeline and the other end of the three-way valve 24 is connected with a lower drainage branch pipe 19; the pressure sensor 11 is n 2.
connected with a collector 12 through a conducting wire, and the collector 12 is connected with a computer control system; and a hydraulic cavity volume adjusting cylinder 5 and a full-automatic hydraulic controller 6 of a lateral pressurizing device are connected with the inner cavity of the pressure cabin 2 through the pipeline and a valve respectively The upper water-permeating plate component, comprising the upper water-permeating annular plate 15, and the upper water-permeating inner plate 20 is sheathed in the upper water-permeating annular plate 15.
The lateral pressurizing device, which is as follows: the hydraulic cavity volume adjusting cylinder S is connected with the inner cavity of the pressure cabin 2 through the pipeline and a water inlet valve 13, and a full-automatic hydraulic controller 6 is connected with the other side of the inner cavity of the pressure cabin 2 through the pipeline and the valve.
The above said components can complete the gravity pressure state for recovering the test sample soil.
The testing device for the coefficient of subgrade reaction test further comprises a vertical pressurizing device, and the vertical pressurizing device includes: a local section pressurizing plate force transmitting column 18 arranged on the inner pressure plate 21, the top end of force transmitting column 18 of the local section pressurizing plate being in contact with a pressurizing support 1, a displacement sensor clamp 7 arranged on the local section pressurizing plate force transmitting colunm 18, displacement sensors 8 arranged at the two ends of the displacement sensor clamp 7, and the displacement sensors 8 being in contact with the upper plane of the pressure cabin 2; the lower part of the pressurizing support 1 being connected with a hanging disk 3, and a weight 4 is placed on the hanging disk 3; and the displacement sensors 8 being connected with the collector 12 through the conducting wires.
The inner cavity of the pressure cabin 2 can be a spherical inner cavity or an inner cavity with the spherical crown-shaped upper part, the spherical crown-shaped lower part and the cylindrical middle part.
The testing method and device for the coefficient of subgrade reaction test has the advantages that the device of the invention is simple in structure, convenient to use and short in test cycle, the test results are equivalent to the in-situ 3O test results, and the coefficient of subgrade reaction of the foundation soil and the foundation bearing capacity can be reflected more precisely; the test principle of the method of the invention is in line with the basic theory; through three times of actual verification from January, 2008 to June, 2009, the test results were proved to tally with the IC3 standard; and the method is fast, simple and accurate in determination of the coefficient of subgrade reaction.
Brief Description of the Drawinu
Figure 1 is a schematic diagram of structure of testing device for coefficient of subgrade reaction test.
Detailed Description of the Invention
Embodiment 1 As shown in Figure 1, a testing method for a coefficient of subgrade reaction test comprises the following steps: (1) Assembling a container according to requirements and filling up degassed distilled water into a hydraulic cavity volume adjusting cylinder; opening a water inlet valve, filling up degassed water into a pressure cabin and removing all bubbles; placing a standard correction test sample (t1 00mm and h=lSOmm) into the container; exerting lateral pressure stage by stage by 100KPa/min up to 800KPa and keeping 800KPa pressure for 10 minutes on the premise of having no water leakage; and relieving pressure and taking out the correction block; (2) Preparing a test sample (D=95mm and h=l2Omm), keeping the two ends of the test sample leveled and sticking 15 fiher paper strips (b=Srnrn) around it; and removing gas in the pipeline and loading the test sample according to the requirements; (3) Hoisting the hydraulic cavity volume adjusting cylinder so as to enable the liquid level to be 30cm higher than the top end of the test sample, to enable a cylindrical latex thin film to be in complete contact with the test sample and to generate contact pressure at about 3KPa, and to close the water inlet valve; (4) Applying full-section vertical load on an upper water-permeating plate component stage by stage till gravity pressure of soil, wherein the gravity pressure of the soil is divided into 1-5 stages according to positions where soil samples are located; (5) Applying load for each stage for one hour, then commencing measuring and recording the hourly lateral pressure and lower-end water displacement; judging stability according as the difference between the water displacement in two hours is less than 0. lml or the residual value of bottom hole pressure is not more than 5% of the vertical pressure, and applying load for next stage; (6) Locking an outer pressure plate after consolidation of the test sample is stable under the action of the gravity pressure and opening a full-automatic hydraulic controller to stabilize the lateral pressure of the test sample at the endpoint value during self-weight consolidation; (7) Reliving the axial pressure, exerting the axial pressure on the test sample by a force transmitting colunm of a local section loading plate in 10 stages till breakage of the test sample; (8) Applying load for each stage by 1', 2', 5', 10', 30', lh, 2h, 3h, ... ; recording the axial deformation value under the corresponding load, and applying load for next stage if stability is confirmed when deformation increment per 2 minutes is less than 0.1mm, or if deformation is not greater than 0.1mm under measurements of deformation at 2-minute interval till the breakage of the test sample; (9) Drawing a P-S curve; (10) Determining the coefficient of subgrade reaction of foundation soil and the foundation bearing capacity according to characteristic points of the P-S curve.
When the deformation increment per hour is less than 0.0 1mm and the stability is confirmed, the slope of a regression straight line of all points before critical edge load is taken as the coefficient of subgrade reaction and then the calculation is directly performed according to a formula of 1(30 in the Specification. P20
From a deformation modulus calculation formula of a shallow plate load test S, we can get K30 =2-.K50 That is, the corresponding pressure deformation amount of a simulation load test amplified by 6 times corresponds to the in-situ 1(30 curve.
A testing device for the coefficient of subgrade reaction test comprises a pressure cabin 2, wherein a cylindrical latex thin film 17 is stuck in an inner cavity of the pressure cabin 2, a lower water-permeating plate 14, a test sample 9 and an upper water-permeating plate component are sequentially arranged on the base of the inner cavity of the pressure cabin 2 from bottom to top, an outer pressure plate 16 is connected on an upper water-permeating annular plate 15 of the upper water-permeating plate component, an inner pressure plate 21 is connected on an upper water-permeating inner plate 20, the outer pressure plate 16 is sheathed outside the inner pressure plate 21, a flange plate 22 is sheathed on a force transmitting sleeve of the outer pressure plate 16, the flange plate 22 is in bolted connection with the pressure cabin 2, and a support bolt 23 arranged on the flange plate 22 is in contact with the outer pressure plate 16; a slot is formed in the base of the pressure cabin 2, a water outlet pipe 10 is arranged in the slot, a three-way valve 24 is arranged on the water outlet pipe 10, one end of the three-way valve 24 is connected with a pressure sensor 11 through a pipeline and the other end of the three-way valve 24 is connected with a lower drainage branch pipe 19; the pressure sensor 11 is connected with a collector 12 through a conducting wire, and the collector 12 is connected with a computer control system; and a hydraulic cavity volume adjusting cylinder 5 and a full-automatic hydraulic controller 6 of a lateral pressurizing device are connected with the inner cavity of the pressure cabin 2 through the pipeline and a valve respectively.
The upper water-permeating plate component comprises the upper water-permeating annular plate 15 and the upper water-permeating inner plate 20 sheathed in the upper water-permeating annular plate 15.
The lateral pressurizing device is as follows: the hydraulic cavity volume adjusting cylinder 5 is connected with the inner cavity of the pressure cabin 2 through the pipeline and a water inlet valve 13, and the full-automatic hydraulic controller 6 is connected with the other side of the inner cavity of the pressure cabin 2 through the pipeline and the valve.
The above said components can complete the gravity pressure state for recovering the test sample soil.
Embodiment 2 As shown in Figure 1, a testing method for a coefficient of subgrade reaction test comprises the following steps: (1) Assembling a container according to requirements and filling up degassed distilled water into a hydraulic cavity volume adjusting cylinder; opening a water inlet valve, filling up degassed water into a pressure cabin and removing all bubbles; placing a standard correction test sample (b 100mm and h=lSOmm) into the container; exerting lateral pressure stage by stage by 100KPa/min up to 800KPa and keeping 800KYa pressure for 10 minutes on the premise of having no water leakage; and relieving the pressure and taking out the correction block; (2) Preparing the test sample (t'=lOOmm and h=lSOmm), keeping the two ends of the test sample leveled and sticking 18 filter paper strips (b=Smm) around it; and removing gas in the pipeline and loading the test sample according to the requirements; (3) Hoisting the hydraulic cavity volume adjusting cylinder so as to enable the liquid level to be 50cm higher than the top end of the test sample, to enable a cylindrical latex thin film to be in complete contact with the test sample and to generate contact pressure at about SKPa, and to close the water inlet valve; (4) Applying full-section vertical load on an upper water-permeating plate component stage by stage up to gravity pressure of soil, wherein the gravity pressure of the soil is divided into 1-5 stages according to positions of soil samples; (5) Applying load for each stage for one hour, then commencing measuring and recording the hourly lateral pressure and lower-end water displacement; judging stability according as the difference between the water displacement in two hours is less than 0. lml or the residual value of bottom hole pressure is not more than 5% of the vertical pressure, and applying load for next stage; (6) Locking an outer pressure plate after consolidation of the test sample is stable under the action of the gravity pressure and opening a full-automatic hydraulic controller to stabilize the lateral pressure of the test sample at the endpoint value during self-weight consolidation.
(7) Reliving the axial pressure, exerting the axial pressure on the test sample by a force transmitting column of a local section loading plate in 12 stages till breakage of the test sample; (8) Applying load for each stage by 1', 2', 5', 10', 30', lh, 2h, 3h, ... ; recording the axial deformation value under the corresponding load, and applying load for next stage if stability is confirmed when deformation increment per 2 minutes is less than 0.1mm, or if deformation is not greater than 0.1mm under measurements of deformation at 2-minute interval till the breakage of the test sample; (9) Drawing a P-S curve; (10) Determining the coefficient of subgrade reaction of foundation soil and the foundation bearing capacity according to characteristic points of the P-S curve.
When applying load for next stage till the breakage of the test sample by assuming the stability criteria as deformation no greater than 0.1mm under measurements of deformation at 2-minute interval, the deformation under each stage of the pressure is to be amplified by six times and then the calculation is directly performed according to a formula of JC3 in the Specification.
1? =I0(l_v2)N From a deformation modulus calculation formula of a shallow plate load test S,we can get K30 -That is, the corresponding pressure deformation amount of a simulation load test amplified by 6 times corresponds to the in-situ C30 curve.
A testing device for the coefficient of subgrade reaction test comprises a pressure cabin 2, wherein a cylindrical latex thin film 17 is stuck in an inner cavity of the pressure cabin 2, a lower water-permeating plate 14, a test sample 9 and an upper water-permeating plate component are sequentially arranged on the base of the inner cavity of the pressure cabin 2 from bottom to top, an outer pressure plate 16 is connected on an upper water-permeating annular plate 15 of the upper water-permeating plate component, an inner pressure plate 21 is connected on an upper water-permeating inner plate 20, the outer pressure plate 16 is sheathed outside the inner pressure plate 21, a flange plate 22 is sheathed on a force transmitting sleeve of the outer pressure plate 16, the flange plate 22 is in bolted connection with the pressure cabin 2, and a support bolt 23 arranged on the flange plate 22 is in contact with the outer pressure plate 16; a slot is formed in the base of the pressure cabin 2, a water outlet pipe 10 is arranged in the slot, a three-way valve 24 is arranged on the water outlet pipe 10, one end of the three-way valve 24 is connected with a pressure sensor 11 through a pipeline and the other end of the three-way valve 24 is connected with a lower drainage branch pipe 19; the pressure sensor 11 is connected with a collector 12 through a conducting wire, and the collector 12 is connected with a computer control system; and a hydraulic cavity volume adjusting cylinder S and a full-automatic hydraulic controller 6 of a lateral pressurizing device are connected with the inner cavity of the pressure cabin 2 through the pipeline and a valve respectively.
The upper water-permeating plate component comprises the upper water-permeating annular plate 15 and the upper water-permeating inner plate 20 sheathed in the upper water-permeating annular plate 15.
The lateral pressurizing device is as follows: the hydraulic cavity volume adjusting cylinder 5 is connected with the inner cavity of the pressure cabin 2 through the pipeline and a water inlet valve 13, and the full-automatic hydraulic controller 6 is connected with the other side of the inner cavity of the pressure cabin 2 through the pipeline and the valve.
The above said components can complete the gravity pressure state for recovering the test sample soil.
The testing device for the coefficient of subgrade reaction test, further comprising a vertical pressurizing device, and the vertical pressurizing device, is as follows: a local section pressurizing plate force transmitting column 18 is arranged on the inner pressure plate 21, the top end of the local section pressurizing plate force transmitting column 18 is in contact with a pressurizing support 1, a displacement sensor clamp 7 is arranged on the local section pressurizing plate force transmitting column 18, displacement sensors 8 are arranged at the two ends of the displacement sensor clamp 7, and the displacement sensors 8 are in contact with the upper plane of the pressure cabin 2; the lower part of the pressurizing support 1 is connected with a hanging disk 3 and a weight 4 is placed on the hanging disk 3; and the displacement sensors 8 are connected with the collector 12 through the conducting wires.
The P-S curve is drawn according to data obtained by all the components, and the coefficient of subgrade reaction of the foundation soil and the foundation bearing capacity are further determined according to the deformation modulus calculation formula of the shallow plate load test.
Embodiment 3 As shown in Figure 1, a testing method for a coefficient of subgrade reaction test comprises the following steps: (1) Assembling a container according to requirements and filling up degassed distilled water into a hydraulic cavity volume adjusting cylinder; opening a water inlet valve, filling up degassed water into a pressure cabin and removing all bubbles; placing a standard correction test sample (I 100mm and h=lSOmm) into the container; exerting lateral pressure stage by stage by 100KPa/min up to 800KPa and keeping 800KYa pressure for 10 minutes on the premise of having no water leakage; and relieving the pressure and taking out a correction block; (2) Preparing the test sample (D=98mm and h=120-lSOmm), keeping the two ends of the test sample leveled and sticking 16 filter paper strips (b=Smm) around it; and removing gas in the pipeline and loading the test sample according to the requirements; (3) Hoisting the hydraulic cavity volume adjusting cylinder so as to enable the liquid level to be 40cm higher than the top end of the test sample, to enable a cylindrical latex thin film to be in complete contact with the test sample and to generate contact pressure at about 4KPa, and to close the water inlet valve; (4) Applying full-section vertical load on an upper water-permeating plate component stage by stage up to gravity pressure of soil, wherein the gravity pressure of the soil is divided into 1-5 stages according to positions of soil samples; (5) Applying load for each stage for one hour, then commencing measuring and recording the hourly lateral pressure and lower-end water displacement; judging stability according as the difference between the water displacement in two hours is less than 0. lml or the residual value of bottom hole pressure is not more than 5% of the vertical pressure, and applying load for next stage; (6) Locking an outer pressure plate after consolidation of the test sample is stable under the action of the gravity pressure and opening a full-automatic hydraulic controller to stabilize the lateral pressure of the test sample at the endpoint value during self-weight consolidation.
(7) Reliving the axial pressure, exerting the axial pressure on the test sample by a force transmitting colunm of a local section loading plate in 11 stages till breakage of the test sample; (8) Applying load for each stage by 1', 2', 5', 10', 30', lh, 2h, 3h, ... ; recording the axial deformation value under the corresponding load, and applying load for next stage if stability is confirmed when deformation increment per 2 minutes is less than 0.1mm, or if deformation is not greater than 0.1mm under measurements of deformation at 2-minute interval till the breakage of the test sample; (9) Drawing a P-S curve; (10) Determining the coefficient of subgrade reaction of foundation soil and the foundation bearing capacity according to characteristic points of the P-S curve.
When applying load for next stage till the breakage of the test sample by assuming the stability criteria as deformation no greater than 0.1mm under measurements of deformation at 2-minute interval, the deformation under each stage of the pressure is to be amplified by six times and then the calculation is directly performed according to a formula of 1C3 in the Specification.
E0 =I0(1_v2) From a deformation modulus calculation formula of a shallow plate load test S,we can get K30 = That is, the corresponding pressure deformation amount of a simulation load test amplified by 6 times corresponds to the in-situ curve.
A testing device for the coefficient of subgrade reaction test comprises a pressure cabin 2, wherein a cylindrical latex thin film 17 is stuck in an inner cavity of the pressure cabin 2, a lower water-permeating plate 14, a test sample 9 and an upper water-permeating plate component are sequentially arranged on the base of the inner cavity of the pressure cabin 2 from bottom to top, an outer pressure plate 16 is connected on an upper water-permeating annular plate 15 of the upper water-permeating plate component, an inner pressure plate 21 is connected on an upper water-permeating inner plate 20, the outer pressure plate 16 is sheathed outside the inner pressure plate 21, a flange plate 22 is sheathed on a force transmitting sleeve of the outer pressure plate 16, the flange plate 22 is in bolted connection with the pressure cabin 2, and a support bolt 23 arranged on the flange plate 22 is in contact with the outer pressure plate 16; a slot is formed in the base of the pressure cabin 2, a water outlet pipe 10 is arranged in the slot, a three-way valve 24 is arranged on the water outlet pipe 10, one end of the three-way valve 24 is connected with a pressure sensor 11 through a pipeline and the other end of the three-way valve 24 is connected with a lower drainage branch pipe 19; the pressure sensor 11 is connected with a collector 12 through a conducting wire, and the collector 12 is connected with a computer control system; and a hydraulic cavity volume adjusting cylinder 5 and a full-automatic hydraulic controller 6 of a lateral pressurizing device are connected with the inner cavity of the pressure cabin 2 through the pipeline and a valve respectively.
The upper water-permeating plate component comprises the upper water-permeating annular plate 15, and the upper water-permeating inner plate 20 is sheathed in the upper water-permeating annular plate.
The lateral pressurizing device is as follows: the hydraulic cavity volume adjusting cylinder 5 is connected with the inner cavity of the pressure cabin 2 through the pipeline and a water inlet valve 13, and the full-automatic hydraulic controller 6 is connected with the other side of the inner cavity of the
S
pressure cabin 2 through the pipeline and the valve.
The above components can complete the gravity pressure state for recovering the test sample soil.
Test Verification In order to inspect the correctness of test analysis, field and indoor contrastive test research was subsequently performed three times from September, 2008 to May, 2009.
A first lot with formation stability, which was 80m long and 15m wide, was selected from a Zhanjiang construction site during September-October, 2009 and six measuring points were uniformly distributed along a long shaft. A 1(30 load test was performed on each measuring point once within the range of 1. lm-1.6m respectively, and original samples were taken from 1# and 3# test pits for performing indoor triaxial tests and simulation load tests (equal-strain control is adopted as stability criteria); in order to analyze deformation characteristics of saturated soft soil under the action of unilateral load, the relationship between deformation and time was recorded during the tests, and the test results are shown in the following table: _________________ ___________ In-situ Load test Result Table (A) ___________ _________ No. of Measuring 1 2 3 4 5 6 Average Point ____ _____ ____ ____ ____ ____ ____ ____ ____ _____ _____ _____ Value Depthof 1.1 1.6 1.1 1.6 1.1 1.6 1.1 1.6 1.1 1.6 1.1 1.6 Measured Point -1.6 -2.3 -1.6 -2.3 -1.6 -2.3 -1.6 -2.3 -1.6 -2.3 -1.6 -2.3 m-m Coefficient of subgradereaction 9.8 11.7 7.5 11.2 14.3 10.9 11.3 8.5 9.3 14.2 16.1 21.0 12.2 K30 MPa/m ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ _______ __________ __________ Indoor Test Result Table (B) __________ ___________ No. of Liquid Plastic Liquidity Plasticity Triaxial Simulation Soil Limit Limit Index Index Test K load K Sample ________ ________ -MPa/m MPa/m 1 47.8 19.2 28.6 0.96 15.6 17.8 2 43.4 18.2 25.2 1.00 18.1 14.7 3 48.4 23.0 25.4 1.17 16.8 16.8 4 49.3 26.7 22.6 1.20 15.6 10.9 47.2 26.1 21.1 1.11 6.8 12.2 6 45.9 25.4 20.5 1.10 11.8 8.8 7 43.9 24.4 19.5 0.89 8.1 14.3 8 30.3 16.4 13.9 0.76 4.7 8.6 9 38.5 19.9 18.6 1.15 12.8 12.8 29.6 16.4 13.2 0.77 12.8 __________ 11 47.9 25.7 22.2 0.85 8.4 _________ 12 36.4 22.7 13.7 1.14 10.6 __________ 13 48.8 29.2 19.6 0.79 _________ __________ 14 43.6 25.7 17.9 1.32 _________ _________ 42.1 23.6 18.5 1.19 _________ __________ Average 118 130 Value _________ _________ _________ _________ _________ _________ The second verification test was performed indoors during January-March, 2009, 10 silt first-stage test samples were firstly taken from the Zhanjiang construction site by using a 108mm thin-wall soil sampler and then the simulation load tests (equal degree consolidation method) and consolidation tests were performed indoors_respectively. The test results are shown in_the_following_table: No. of Soil Natural Liquid Plastic Plasticity Liquidity Comprcssion Static Coefficient of Coefficient Denomination Soil Sampling void Limit Limit Index Index Modulus Lateral subgrade reaction of Sample Depth Ratio Es12 Pressure (Equal-consolidation subgrade (m-m) Co Degree) reaction K=4.25 ______ _______ ______ _____ _____ _______ _______ _________ ______ ______________ (lICo2) Es 14-3 2.7-3+0 2.089 63.0 33.7 29+3 1,43 1.1 0.56 6.1 3.21 Silt 14-4 3.0-3.3 1.865 54.6 27.6 27.0 1.51 1.5 0.56 1.6 4.38 Silt 14-9 4.5-5.8 2.226 57.5 34.2 33.3 1.42 1.1 0.57 8.1 3.16 Silt 23-ZR 4.3-4.6 2.366 60.9 30.1 30.8 1.77 1.0 0.50 5.7 3.19 Silt 14-2 2.4-2.7 1.722 54.1 28.3 25.8 1.38 1.7 0.51 6.8 5.35 Silt 15-lA 2.0-2.30 1.516 54.4 27.6 26.8 0.94 3.2 0.49 4.3 10.33 Clay 15-lB 2.3-2.6 2.713 76,2 29.3 46.9 1.00 1.5 0.52 1.5 4.65 Clay l5-1C 2.6-2.9 1.610 69.2 25.2 44,0 0.78 1.6 0.55 1.9 4.73 Clay 96-6 4.5-4.8 1.202 36.4 20.4 16.0 1.39 2,8 0.47 12.5 9.27 Mucky Clay Averagevalue 1.72 0.53 5.39 5.26 The third verification test was performed for the South-North industry transfer technical transformation project in Hualing Tin Steel Group Co., Ltd. during March-July, 2009 and was divided into four subareas, namely an electric furnace steelmaking area, a 258mm hot continuous rolling area, a bar workshop and a whole-factory public and auxiliary facility and pipe network area. The simulation load tests at this time were completely controlled by adopting the equal degree consolidation method, and the detailed test results are shown in the following table: Load Test and Simulation Load Test Result Table in 258mm Hot Continuous Rolling Area and Physical Index Test Result Table of Test Soil No. Natural Natural. Natural K30 Liquid Plastic Plasticity Liquidity Actual Simulation of Sampling Water Unit Void Limit Limit Index Index Measured load Category Test Depth Content Weight Ratio Value of Soil Point _____ _________ % kN/m3 _______ ______ % ______ ________ _______ MPa/m MPa/m _______ Mucky 1 1.20-1,40 36.3 1S.0 2.72 1.018 32.6 22.2 10.4 1.36 8.4 8.2 Sihy ______ __________ _______ _______ _______ _______ ______ ______ _________ ________ _________ __________ Clay 2 1.10-1,30 33.9 18.5 2.72 0.929 33.6 21.1 12.5 1.02 12.3 13.7 Sihy ______ __________ _______ _______ _______ _______ ______ ______ _________ ________ _________ __________ Clay Mucky 3 1.10-1.30 42.2 17.7 2.73 1.149 36.2 22.0 14.2 1.42 8.2 9.0 Silty ______ __________ _______ _______ _______ _______ ______ ______ _________ ________ _________ __________ Clay Mucky 4 1.10-1,30 45.0 17.4 2.73 1.230 39.9 24.7 15.2 1.34 8.0 10.8 Silty ______ __________ _______ _______ _______ _______ ______ ______ _________ ________ _________ __________ Clay Mucky 2.00 40.7 17.5 2.73 1.151 38.0 22.1 15.9 1.17 9.6 Silty __________ _______ _______ _______ _______ ______ ______ _________ ________ _________ __________ Clay Mucky 3.00-3.30 40.1 17.4 2.73 1.154 37.5 22.7 14.8 1.18 8.9 Silty ______ __________ _______ _______ _______ _______ ______ ______ _________ ________ _________ __________ Clay Mucky 2.00 40.0 17.7 2.73 1.116 38.7 23.0 15.7 1.08 13.2 Silty __________ _______ _______ _______ _______ ______ ______ _________ ________ _________ __________ Clay Mucky 5.00-5.30 37.6 17.8 2.73 1.068 36.7 21.8 14.9 1.06 13.7 Silty ______ __________ _______ _______ _______ _______ ______ ______ _________ ________ _________ __________ Clay Mucky 3.00 42.1 17.8 2.73 1.136 37.9 23.1 14.8 1.28 11.6 Silty 7 _________ _______ _______ _______ ______ ______ ______ ________ ________ ________ _________ Clay 6.00-6.30 35.3 18.2 2.72 0.982 32.1 20.6 11.5 1.28 24.9 Sihy ______ __________ _______ _______ _______ _______ ______ ______ _________ ________ _________ __________ Clay Mucky 1.00 41.0 17.7 2.73 1.131 39.9 24.0 15.9 1.07 9.8 Silty 8 _________ _______ _______ _______ ______ ______ ______ ________ ________ ________ _________ Clay 4.00-4.30 33.4 17.9 2.72 0.987 33.2 22.6 10.6 1.02 15.5 Sihy ______ __________ _______ _______ _______ _______ ______ ______ _________ ________ _________ __________ Clay Mucky 2.00 40.7 17.8 2.73 1.115 38.2 23.0 15.2 1.16 8.6 Silty 9 ________ _________ Clay Mucky 5.40-5.70 40.8 17.4 2.73 1.165 37.6 23.1 14.5 1.22 8.7 Silty ______ __________ _______ _______ _______ _______ ______ ______ _________ ________ _________ __________ Clay Mucky 1.00 40.0 17.8 2.73 1.104 38.8 23.0 15.8 1.08 7.5 Silty ________ _________ Clay Mucky 3.30-3.60 39.2 17.5 2.73 1.128 36.5 23.0 13.5 1.20 7.8 Silty ______ __________ _______ _______ _______ _______ ______ ______ _________ ________ _________ __________ Clay Load Test and Simulation Load Test Result Table in Whole-factory Public and Auxiliary Facility and Pipe Network Area and Physical Index Test Result Table _____ ________ _______ _______ _______ _______ of Test Soil ________ ________ ________ _________ ________ No. Natural Natural. Natural I(10 Liquid Plastic Plasticity Liquidity Actual Simulation of Sampling Water Unit Void Limit Limit Index Index Measured load Category Test Depth Content Weight Ratio of Soil ________ ________ ________ ________ _______ _______ _________ _________ Value __________ Point _____ ________ % kN/m3 _______ ______ ______ ______ _______ _______ MPa/m MPa/m _______ Mucky 2,00 45,0 17.5 2.73 1.211 38.2 22.0 16.2 1.42 11.0 Silty ________ _______ ______ _______ ______ ______ ______ _______ _______ ________ _________ Clay Mucky 4.00-4.30 43.8 17.3 2.73 1.218 36.7 21.6 15.1 1.47 10.2 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay Mucky 2 1.00 39.8 17.9 2.72 1.078 35.2 22.0 13.2 1.35 9.2 Silty _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay _____ 3.00-3.30 34.0 18.1 2.71 0.963 28.7 19.0 9.7 1.55 _________ 31.3 Silt 2.00 36.4 17.9 2.73 1.035 38.6 22.1 16.5 0.87 14.5 Silty 3 _______ _________ Clay 4.00-4,30 29.7 18.2 2.72 0.897 34.7 21.1 13.6 0.63 21.4 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay 2.00 34.7 18.0 2.72 0.991 35.1 22.0 13.1 0.97 16.0 Silty 4 ________ _________ Clay 6.00-6.30 32.7 18.2 2.72 0.941 33.6 22.5 11.1 0.92 18.9 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay Mucky 2.00 37.6 17.5 2.72 1.091 35.2 21.6 13.6 1.18 9.8 Silty ________ _______ ______ _______ ______ ______ ______ _______ _______ ________ _________ Clay 6.00-6.30 34.1 18.2 2.72 0.961 36.8 23.2 13.6 0.80 13.6 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay Load Test and Simulation Load Test Result Table in Electric Furnace ____ _______ Steelmaking Area and Physical_Index Test Result Table of Test Soil ________ _______ No. Natural Natural Natural (10 Specific Liquid Plastic Plasticity Liquidity Actual Simulation of Sampling Water Unit Limit Limit Index Index Measured load Category Weight Void Test Depth Content Weight Ratio Value of Soil Point _____ ________ % kN/m3 _______ ______ ______ ______ _______ _______ MPa/m MPa/m _______ Mucky 1 1.20-1.40 36.3 18.0 2.72 1.015 32.6 22.2 10.4 1.36 8.4 8.2 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay 2 1.10-1.30 33.9 18,5 2.72 0.927 33.6 21.1 12.5 1.02 12.3 13.7 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay Mucky 3 1.10-1.30 42.2 17.7 2.73 1.145 36.2 22.0 14.2 1.42 8.2 9.0 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay Mucky 4 1.10-1.30 45.0 17.4 2.73 1.224 39.9 24.7 15.2 1.34 8.0 10.8 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay 2.00-2.20 33.9 18.3 2.73 0.955 37.1 21.7 15.4 0.79 24.6 20.2 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay 6 2.00-2.20 37.8 17.8 2.73 1.067 38.1 23.0 15.1 0.98 13.9 14.7 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay 7 2.00-2,20 37.6 17.6 2.73 1.087 39.0 23.6 15.4 0.91 20.3 21.4 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay 8 2.00-2.20 36.3 18.4 2.72 0.972 35.7 22.0 13.7 1.04 9.2 8.9 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay 9 2.00-2.20 34.5 17.6 2.73 1.040 37.8 23.0 14.8 0.78 8.7 8.0 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay 2.00-2,20 33.6 17.9 2.73 0.993 34.7 20.1 14.6 0.92 18.2 17.8 Silty _____ _________ _______ _______ _______ _______ _____________ ________ ________ ________ _________ Clay Load Test and Simulation Load Test Result Table in Bar Workshop and Physical _____ ________ _______ ______ Index Test Result Table of Test Soil ________ _________ _______ No. Natural Natural Natural (10 Specific Liquid Plastic Plasticity Liquidity Actual Simulation of Sampling Water Unit Limit Limit Index ludex Measured load Category Weight Void Test Depth Content Weight Ratio Value of Soil Point _____ ________ % kN/m3 _______ ______ ______ ______ _______ _______ MPa/m MPa/m _______ 2.00 38.0 17,5 2.73 1.105 38.5 22.1 16.4 0.97 17.2 Silty _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay Mucky 3.00-3.30 42.9 17.3 2.73 1.204 38.4 22.7 15.7 1.29 9.6 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay 2.00 35.3 17.5 2.73 1.064 36.4 21.7 14.7 0.93 13.6 Silty _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay 2 Mucky 3.30-3.60 39.2 17.5 2.73 1.123 33.5 19.0 14.5 1.39 10.3 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay Mucky 2.00 40.4 17.8 2.73 1.106 39.1 23.0 16.1 1.08 9.2 Silty 3 _______ _________ Clay Mucky 3.00-3.30 36.2 17.4 2.73 1.089 34.5 22.7 11.8 1.14 8.6 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay 2.00 31.6 17.6 2.73 0.996 36.4 22.2 14.2 0.66 19.3 Silty 4 ________ _________ Clay 6.00-6.30 33.5 17.9 2.73 0.992 36.0 20.4 15.6 0.84 17.4 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay Mucky 4.00-4.30 42.1 17.3 2.73 1.192 38.4 23.0 15.4 1.24 11.8 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay Mucky 6 4.00-4.30 35.4 17.9 2.72 1.013 33.2 22.6 10.6 1.21 11.3 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay 7 4.004,30 32.5 18.2 2.72 0.938 33.1 21.6 11.5 0.95 12.7 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay 8 6.00-6.30 32.4 18.1 2.72 0.947 34.0 22.7 11.3 0.86 18.5 Silty _____ _________ _______ _______ _______ _______ ______ ______ ________ ________ ________ _________ Clay _____________ Statistical Table of Third Verification Test _____________ Soil Layer K3o Average Simulation Es12 Static K4.25 Value load K Average Lateral (1-K02) Es Average Value Pressure K0 Value Average __________ __________ __________ __________ Value __________ Mucky Silty 8.75 9.8 3.4 0.54 10.2 Clay __________ __________ __________ __________ __________ SiltyClay 15.4 16.3 5.1 0.54 15.35 Note: (1) Es12 and K0 values are statistical average values in the investigation report.
(2) The coefficient of subgrade reaction value is pressure to deformation ratio with settlement 1.25mm.
During the first verification test, the indoor simulation load test adopted the equal-strain method to control loading, namely the deformation per hour did not exceed 0.0 1mm, and load for next stage was applied till the breakage of the test sample; generally, 7-10 days are consumed for making a group of the sample; in the table, the coefficient of subgrade reaction value is the slope of the straight line section before critical edge load, and the comparative test results are equivalent, indicating that the coefficient of subgrade reaction determined by adopting the simulation load test through the equal-strain method indoors is equivalent to the in-situ 1(30 value.
The second verification test adopted 9 samples in total, the consolidation tests were performed respectively and the simulation load tests controlled by equal degree consolidation (namely the value was measured and read once every two minutes, if the deformation was not more than 0.1mm during the continuous two 2-minute intervals, then load for next stage would be applied) were adopted. As a thin layer of sihy sand and sih is included at the center of each test sample, the K value of the same soil, which is measured by simulation load, is greatly different from the K=4.25 (1-K02)Esi2, but the mathematical average values corresponding to the two are almost the same, due mainly to the diversity of the samples.
During the third verification test, which was performed by combining with production tasks, 25 groups of I(3 tests were performed in total; and study objects of 29 groups of the simulation load tests were silty clay layers and mucky sihy clays within the range of 1.0-5.Om under the ground. The Es12 average value in the geotechnical test resuhs in the space investigation report is used for calculating the coefficient of subgrade reaction according to the formula K=4.25 (1-K02) Es, and the coefficient of subgrade reaction values obtained by the three tally with each other substantially and are within the range of recommended values of the Specification, indicating that the simulation load tests adopting the equal-degree-consolidation control method and the formula K=4.25 (11(o2) Es12 are feasible.
By analyzing the consolidation tests and the characteristics of deformation and time under load for each stage in the simulation load tests and by transforming the coordinates, we can find that the reciprocal of the ratio of settlement at a certain time to the elapsed time is in linear relationship with the elapsed time in a rectangular t/t,s=at-i-b=Ess= coordinate system, namely: at + b As=i When t-*oc, a, namely the test sample has a theoretic maximum compression amount under the action of certain single uniformly distributed load.
Through comparative analysis of the K30 load, the simulation load and the formula [K 4.25(1_Ka2)Es1 we can find that thc adoption of the simulation load and the formula for calculating the coefficient of subgrade reaction is feasible; however, the consumed time is too long when the equal-strain method is adopted, so that the equal-strain method is inconvenient to use during the actual applications and the equal-degree-consolidation control method is a better choice.
[Kt4.25(l_1ca2)EsI.
As for the formula, only the comparison with normally consolidated soil was performed in the verification test at this time, and the formula is only suitable for the normally-consolidated soil and can not be used for over-consolidated soil.
Claims (5)
- Claims 1. A testing method for coefficient of subgrade reaction test comprising the following steps: (1) Assembling a container according to requirements and filling up degassed distilled water into a hydraulic cavity volume adjusting cylinder; opening a water inlet valve, filling up degassed water into a pressure cabin and removing all bubbles; placing a standard correction test sample into the container; exerting lateral pressure stage by stage by 100KPa/min up to 800KPa and keeping 800KPa pressure for 10 minutes without any water leakage; and relieving the pressure and taking out the correction block; (2) Preparing a test sample, keeping the two ends of the test sample leveled and sticking 15-18 filter paper strips on the periphery of the test sample; and removing gas in pipeline and loading the test sample according to the requirements; (3) Hoisting the hydraulic cavity volume adjusting cylinder so as to enable the liquid level to be 30-50cm higher than the top end of the test sample, to enable a cylindrical latex thin film to be in complete contact with the test sample and to generate contact pressure at about 3-SKPa, and to close the water inlet valve; (4) Applying full-section vertical load on an upper water-permeating plate component stage by stage up to gravity pressure of soil, wherein the gravity pressure of the soil is divided into 1-5 stages according to positions of soil samples; (5) Applying load for each stage for one hour, then commencing measuring and recording the hourly lateral pressure and lower-end water displacement; judging stability according as the difference between the water displacement in two hours is less than 0. lml or the residual value of bottom hole pressure is not more than 5% of the vertical pressure, and applying load for next stage; (6) Locking outer pressure plate after consolidation of the test sample is stable under the action of the gravity pressure and opening a full-automatic hydraulic controller to stabilize the lateral pressure of the test sample at the endpoint value during self-weight consolidation.(7) Reliving the axial pressure, exerting the axial pressure on the test sample by a force transmitting column of a local section loading plate in 10-12 stages till breakage of the test sample; (8) Applying load for each stage by 1', 2', 5', 10', 30', lh, 2h, 3h, ... ; recording the axial deformation value under the corresponding load, and applying load for next stage when stability is confirmed if deformation increment per hour is less than 0.0 1mm, or if deformation is not greater than 0.1mm under measurements of deformation at 2-minute interval, till the breakage of the test sample; (9) Drawing a P-S curve; (10) Determining the coefficient of subgrade reaction of foundation soil and the foundation bearing capacity according to characteristic points of the P-S curve.When the deformation increment per hour is less than 0.1mm and the stability is confirmed, the slope of a regression straight line of all points before critical edge load is taken as the coefficient of subgrade reaction; By assuming the stability criteria as deformation no greater than 0.1mm under measurements of deformation at 2-minute interval, load for next stage is applied till the breakage of the test sample, the deformation under each stage of the pressure is to be amplified by six times and then the calculation is directly performed according to aformula of 1(30 in the Specification.
- 2. A testing device for coefficient of subgrade reaction test comprising a pressure cabin (2), wherein a cylindrical latex thin film (17) is stuck in an inner cavity of the pressure cabin (2), a lower water-permeating plate (14), a test sample (9) and an upper water-permeating plate component are sequentially arranged on the base of the inner cavity of the pressure cabin (2) from bottom to top, an outer pressure plate (16) is connected on an upper water-permeating annular plate (15) of the upper water-permeating plate component, an inner pressure plate (21) is connected on an upper water-permeating inner plate (20), the outer pressure plate (16) is sheathed outside the inner pressure plate (21), a flange plate (22) is sheathed on the force transmitting sleeve of the outer pressure plate (16), the flange plate (22) is in bolted connection with the pressure cabin (2), and a support boh (23) arranged on the flange plate (22) is in contact with the outer pressure plate (16); a slot is formed in the base of the pressure cabin (2), a water outlet pipe (10) is arranged in the slot, a three-way valve (24) is arranged on the water outlet pipe (10), one end of the three-way valve (24) is connected with a pressure sensor (11) through pipeline and the other end of the three-way valve (24) is connected with a lower drainage branch pipe (19); the pressure sensor (11) is connected with a collector (12) through conducting wire, and the collector (12) is connected with a computer control system; and a hydraulic cavity volume adjusting cylinder (5) and a full-automatic hydraulic controller (6) of a lateral pressurizing device are connected with the inner cavity of the pressure cabin (2) through pipeline and valve respectively.
- 3. The testing device for coefficient of subgrade reaction test according to claim 2, characterized in that the upper water-permeating plate component comprises the upper water-permeating annular plate (15), and the upper water-permeating inner plate (20) is sheathed in the upper water-permeating annular plate (15).
- 4. The testing device for coefficient of subgrade reaction test according to claim 2, characterized in that the lateral pressurizing device is as follows: the hydraulic cavity volume adjusting cylinder (5) is connected with the inner cavity of the pressure cabin (2) through the pipeline and a water inlet valve (13), and the full-automatic hydraulic controller (6) is connected with the other side of the inner cavity of the pressure cabin (2) through the pipeline and the valve.
- 5. The testing device for coefficient of subgrade reaction test according to claim 2, characterized in that the testing device for the coefficient of subgrade reaction test further comprises a vertical pressurizing device, and the vertical pressurizing device includes: a local section pressurizing plate force transmitting column (18) arranged on the inner pressure plate (21), the top end of the local section pressurizing plate force transmitting column (18) being in contact with a pressurizing support (1), a displacement sensor clamp (7) arranged on the local section pressurizing plate force transmitting column (18), displacement sensors (8) arranged at the two ends of the displacement sensor clamp (7), and the displacement sensors (8) being in contact with the upper plane of the pressure cabin (2); the lower part of the pressurizing support (1) being connected with a hanging disk (3) and a weight (4) being placed on the hanging disk (3); and the displacement sensors (8) being connected with the collector (12) through the conducting wires. is
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| CN101650286A (en) * | 2009-08-26 | 2010-02-17 | 中冶集团武汉勘察研究院有限公司 | Bedding coefficient testing method |
| CN201497679U (en) * | 2009-08-26 | 2010-06-02 | 中冶集团武汉勘察研究院有限公司 | Bedding value experiment testing device |
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- 2010-07-26 WO PCT/CN2010/001125 patent/WO2011022932A1/en active Application Filing
- 2010-07-26 GB GB1205190.0A patent/GB2488053B/en active Active
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| CN101377079A (en) * | 2008-10-08 | 2009-03-04 | 上海市政工程设计研究总院 | Method for measuring foundation bed coefficient indoor |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106442152A (en) * | 2016-09-19 | 2017-02-22 | 南华大学 | Testing apparatus for stably applying osmotic pressure with crack propagation |
| CN106442152B (en) * | 2016-09-19 | 2018-10-19 | 南华大学 | It is a kind of to stablize the experimental rig for applying osmotic pressure with crack propagation |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2011022932A1 (en) | 2011-03-03 |
| GB2488053B (en) | 2013-07-31 |
| GB201205190D0 (en) | 2012-05-09 |
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