CN105092391A - Expansive soil slope shallow-layer damaged soil body shear strength test method - Google Patents

Expansive soil slope shallow-layer damaged soil body shear strength test method Download PDF

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CN105092391A
CN105092391A CN201510513948.1A CN201510513948A CN105092391A CN 105092391 A CN105092391 A CN 105092391A CN 201510513948 A CN201510513948 A CN 201510513948A CN 105092391 A CN105092391 A CN 105092391A
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shear strength
soil
sample
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shallow layer
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肖杰
杨和平
唐咸远
倪啸
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Changsha University of Science and Technology
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Abstract

本发明公开了一种膨胀土边坡浅层破坏土体抗剪强度试验方法,试样首先经真空饱和,然后在水槽中施加与剪切时相应的法向应力浸水固结饱和,使试样充分吸水膨胀完全,再在恒温烘箱中干燥至恒重,如此反复,直至达到预定的干湿循环次数,以真实地反映大气干湿循环的作用。本发明的膨胀土边坡浅层破坏土体抗剪强度试验方法有效法向应力包含反映土体实际受力状态的较低有效法向应力;考虑了大气干湿循环作用,且干湿循环膨胀过程中施加与剪切时法向应力相一致的等效荷载作用;抗剪强度试验结果采用改进的幂函数代替摩尔库伦线性函数进行拟合,能真实反映膨胀土边坡浅层破坏土体实际受力状态下抗剪强度。

The invention discloses a method for testing the shear strength of expansive soil slope shallow layer damaged soil. The sample is first saturated in vacuum, and then the normal stress corresponding to the shearing is applied in a water tank to soak and saturate the sample. Sufficiently absorb water and swell completely, and then dry to constant weight in a constant temperature oven, and so on, until the predetermined number of dry-wet cycles is reached, so as to truly reflect the effect of atmospheric dry-wet cycles. The effective normal stress of the test method for the shear strength of expansive soil slope shallow layer damaged soil of the present invention includes a lower effective normal stress reflecting the actual stress state of the soil; the effect of atmospheric dry-wet cycle is considered, and the dry-wet cycle expands During the process, an equivalent load that is consistent with the normal stress during shearing is applied; the results of the shear strength test are fitted with an improved power function instead of the Mohr-Coulomb linear function, which can truly reflect the actual damage of the expansive soil slope shallow layer. Shear strength under stress.

Description

一种膨胀土边坡浅层破坏土体抗剪强度试验方法A test method for shear strength of expansive soil slope shallow layer failure soil

技术领域technical field

本发明属于道路工程领域,尤其涉及一种膨胀土边坡浅层破坏土体抗剪强度试验方法。The invention belongs to the field of road engineering, and in particular relates to a method for testing the shear strength of expansive soil slope shallow layer damaged soil.

背景技术Background technique

由于膨胀土富含蒙脱石等高亲水性矿物,具有显著的干缩湿胀特性,导致其边坡稳定性的研究比普通粘土边坡复杂得多,尤其是其抗剪强度参数难以准确确定。现行公路路基设计规范(JTGD30-2004)提出膨胀土的抗剪强度指标应采用低于峰值的强度值,也可采取反算或经验确定指标值,暴露出强度参数取值的复杂、难以把握与不确定性;另外,为什么膨胀土边坡坡率放缓至1∶2~1∶3甚至更缓也发生失稳破坏,通常无法解释,规范甚至指出采用常规土力学方法不能妥善解决膨胀土路堑边坡的稳定问题。Because expansive soil is rich in highly hydrophilic minerals such as montmorillonite, and has significant dry shrinkage and wet expansion characteristics, the study of its slope stability is much more complicated than that of ordinary clay slopes, especially its shear strength parameters are difficult to be accurate Sure. The current highway subgrade design code (JTGD30-2004) proposes that the shear strength index of expansive soil should be lower than the peak strength value, and the index value can also be determined by back calculation or experience, which exposes the complexity of the value of the strength parameter, which is difficult to grasp. Uncertainty; in addition, it is usually impossible to explain why expansive soil slopes are destabilized and damaged when the slope ratio slows down to 1:2~1:3 or even slower. slope stability problems.

经大气干湿循环作用,膨胀土边坡常在降雨期或雨后发生破坏,且绝大部分边坡破坏具有浅层性,绝大多数表层坍滑的深度在1.0~2.5m之间,此时作用在滑动面上土体的有效法向应力约为10~30kPa,远小于现行公路土工试验规程(JTGE40-2007)中直剪试验的最小法向应力或常规三轴试验的最小围压(50kPa)。因此,根据现行公路土工试验规程(JTGE40-2007)测试的膨胀土峰值慢剪强度结果甚至是残余强度结果,采用符合摩尔库伦准则的线性方法拟合的强度参数开展膨胀土边坡稳定分析,计算获得的边坡安全系数显著偏大,得不到与边坡发生浅层破坏相符的结果。Under the action of atmospheric dry-wet cycle, expansive soil slopes often fail during the rainfall period or after rain, and most of the slope damage is shallow, and the depth of most surface collapses is between 1.0 and 2.5m. The effective normal stress of the soil acting on the sliding surface is about 10-30kPa, which is much smaller than the minimum normal stress of the direct shear test or the minimum confining pressure of the conventional triaxial test ( 50kPa). Therefore, according to the results of peak slow shear strength and even residual strength of expansive soil tested in the current road geotechnical test code (JTGE40-2007), the slope stability analysis of expansive soil is carried out by using the strength parameters fitted by the linear method conforming to the Mohr-Coulomb criterion. The obtained safety factor of the slope is obviously too large, and the result that is not consistent with the shallow failure of the slope can be obtained.

造成上述现象的原因主要是在膨胀土强度测试时,现行公路土工试验规程(JTGE40-2007)中的慢剪(排水直剪)试验存在以下几点不足:(1)室内试验土体强度测试时的受力状态与实际边坡破坏时土体的实际受力状态不符;(2)采用符合摩尔库伦准则的线性方法拟合强度实验结果不能反映真实状况;(3)没有考虑干湿循环的作用。The reason for the above phenomenon is mainly that the slow shear (drainage direct shear) test in the current road geotechnical test regulations (JTGE40-2007) has the following deficiencies when testing the strength of expansive soil: (1) In the indoor test soil strength test The stress state of the soil is inconsistent with the actual stress state of the soil when the actual slope is damaged; (2) The fitting strength test results using the linear method conforming to the Mohr-Coulomb criterion cannot reflect the real situation; (3) The effect of the dry-wet cycle is not considered .

发明内容Contents of the invention

本发明的目的在于提供一种膨胀土边坡浅层破坏土体抗剪强度试验方法,旨在解决现行公路土工试验规程中的慢剪试验不能真实反映膨胀土边坡浅层破坏土体实际受力状态下抗剪强度的问题。The purpose of the present invention is to provide a method for testing the shear strength of expansive soil slope shallow-layer damaged soil, aiming at solving the problem that the slow shear test in the current road geotechnical test regulations cannot truly reflect the actual damage of expansive soil slope shallow-layer soil. The problem of shear strength under stress.

本发明是这样实现的,一种膨胀土边坡浅层破坏土体抗剪强度试验方法包括:The present invention is achieved in that a kind of expansive soil slope shallow layer failure soil shear strength test method comprises:

步骤一、试样制作:采用环刀削取原状土样,切削时保证试样与环刀壁贴合紧密;平行试验试样的密度差和含水率差分别不大于±0.1g/cm3和1%;Step 1. Sample preparation: Cut the undisturbed soil sample with a ring knife, and ensure that the sample is closely attached to the wall of the ring knife when cutting; the density difference and moisture content difference of the parallel test samples are not greater than ±0.1g/cm 3 and 1%;

步骤二、对试样进行有荷作用干湿循环;Step 2, carry out dry-wet cycle on the sample under load;

步骤三、干湿循环饱和试样在相应垂直压力下饱和固结;Step 3, the dry-wet cycle saturated sample is saturated and consolidated under the corresponding vertical pressure;

步骤四、根据实际抗剪强度大小选择测力环,启动直剪仪,以恒定速度进行剪切,直至获得峰值抗剪强度;Step 4. Select the force measuring ring according to the actual shear strength, start the direct shear instrument, and shear at a constant speed until the peak shear strength is obtained;

步骤五、采用改进的幂函数对试验数据进行拟合。Step 5, using the improved power function to fit the experimental data.

进一步,步骤二所述的对试样进行有荷作用干湿循环的具体方法为:Further, the specific method of carrying out the dry-wet cycle with load on the sample described in step 2 is:

将试样在真空饱和器内抽真空饱和,此时限制试样膨胀,保持体积恒定,真空饱和完成后,再施加与法向应力等效的荷载浸水饱和96h;然后,将充分吸水膨胀饱和试样置于40℃鼓风干燥烘箱中干燥36h,使饱和试样干燥至恒重;重复上述两个步骤多次,直至达到预定的干湿循环次数。Vacuum and saturate the sample in the vacuum saturator. At this time, limit the expansion of the sample and keep the volume constant. After the vacuum saturation is completed, apply a load equivalent to the normal stress and soak in water for 96 hours; Place the sample in a blast drying oven at 40°C for 36 hours to dry the saturated sample to constant weight; repeat the above two steps several times until the predetermined number of drying and wetting cycles is reached.

进一步,步骤二中所述的法向应力为5kPa、15kPa、30kPa、50kPa、100kPa、200kPa和300kPa;预定的干湿循环次数,根据实际情况取4~8次。Further, the normal stress described in step 2 is 5kPa, 15kPa, 30kPa, 50kPa, 100kPa, 200kPa and 300kPa; the predetermined number of drying and wetting cycles is 4 to 8 times according to the actual situation.

进一步,步骤三中所述试样饱和固结条件为试样的垂直变形等于或小于0.003mm/h。Further, the saturated consolidation condition of the sample in step three is that the vertical deformation of the sample is equal to or less than 0.003mm/h.

进一步,步骤四中所述测力环选择是当垂直压力为5kPa、15kPa和30kPa时,选择的测力环最大量程为0.1kN,精度为0.0025kN;其它各垂直压力抗剪强度测试时采用规范常用测力环;恒定速度为0.01mm/h,以保证试样为排水剪切条件,也可根据膨胀土粘粒含量及胀缩等级选择更小值。Further, the selection of the force measuring ring in step 4 is that when the vertical pressure is 5kPa, 15kPa and 30kPa, the maximum range of the selected force measuring ring is 0.1kN, and the accuracy is 0.0025kN; The force measuring ring is commonly used; the constant speed is 0.01mm/h to ensure that the sample is under drainage and shear conditions, and a smaller value can also be selected according to the clay content of expansive soil and the degree of expansion and contraction.

进一步,步骤五中所述改进幂函数为实际操作为将试验测试结果输入origin软件中,自定义上述改进幂函数,以有效法向应力σ为横坐标,抗剪强度τ为纵坐标,采用最小二乘法进行拟合,获得(A,n,T)三参数。Further, the improved power function described in step five is The actual operation is to input the test results into the origin software, customize the above-mentioned improved power function, take the effective normal stress σ as the abscissa, and the shear strength τ as the ordinate, and use the least square method for fitting to obtain (A, n , T) three parameters.

式中:τ是抗剪强度;σ是有效法向应力;Pa是大气压力;(A,n,T)是拟合参数。where: τ is the shear strength; σ is the effective normal stress; P a is the atmospheric pressure; (A, n, T) is the fitting parameter.

进一步,采用极限平衡法分析边坡稳定性,运用geoslope软件自带的非线性强度参数分析功能基于以下两式,获得不同有效法向应力下不同条块土体抗剪强度参数的有效粘聚力c和有效摩擦角Furthermore, the limit equilibrium method is used to analyze the slope stability, and the nonlinear strength parameter analysis function of the geoslope software is used to obtain the effective cohesion of the shear strength parameters of different strips of soil under different effective normal stresses based on the following two formulas c and effective friction angle :

cc == PP aa AA (( σσ PP aa ++ TT )) nno -- σσ ×× AA nno (( σσ // PP aa ++ TT )) (( 11 -- nno )) == AA [[ (( 11 -- nno )) σσ ++ PP aa TT ]] (( σσ // PP aa ++ TT )) (( 11 -- nno ))

式中:c是有效粘聚力;是有效摩擦角;σ是有效法向应力;Pa是大气压力;(A,n,T)是拟合参数。In the formula: c is the effective cohesion; is the effective friction angle; σ is the effective normal stress; P a is the atmospheric pressure; (A, n, T) is the fitting parameter.

本发明的膨胀土边坡浅层破坏土体抗剪强度试验方法有效法向应力包含反映土体实际受力状态的较低有效法向应力;考虑了大气干湿循环作用,且干湿循环膨胀过程中施加与剪切时法向应力相一致的等效荷载作用;抗剪强度试验结果采用改进的幂函数代替摩尔库伦线性函数进行拟合,能真实反映膨胀土边坡浅层破坏土体实际受力状态下抗剪强度。本发明提供的膨胀土边坡浅层破坏土体抗剪强度试验方法,可为膨胀土边坡浅层稳定性分析提供可靠的抗剪强度参数,从而合理解释膨胀土边坡浅层破坏问题,并为土工格栅加筋柔性支护等有效处治措施提供理论支撑。The effective normal stress of the test method for the shear strength of expansive soil slope shallow layer damaged soil of the present invention includes a lower effective normal stress reflecting the actual stress state of the soil; the effect of atmospheric dry-wet cycle is considered, and the dry-wet cycle expands During the process, an equivalent load that is consistent with the normal stress during shearing is applied; the results of the shear strength test are fitted with an improved power function instead of the Mohr-Coulomb linear function, which can truly reflect the actual damage of the expansive soil slope shallow layer. Shear strength under stress. The test method for shear strength of expansive soil slope shallow layer failure soil provided by the present invention can provide reliable shear strength parameters for the stability analysis of expansive soil slope shallow layer, thereby reasonably explaining the problem of expansive soil slope shallow layer failure, And provide theoretical support for effective treatment measures such as geogrid reinforced flexible support.

附图说明Description of drawings

图1是本发明实施例提供的膨胀土边坡浅层破坏土体抗剪强度试验方法流程图;Fig. 1 is the expansive soil slope shallow layer failure soil body shear strength test method flowchart that the embodiment of the present invention provides;

图2是本发明实施例提供的法向应力和抗剪强度对应关系图。Fig. 2 is a diagram of the relationship between normal stress and shear strength provided by the embodiment of the present invention.

具体实施方式Detailed ways

为能进一步了解本发明的发明内容和特点,兹例举以下实施例,并配合附图详细说明如下。In order to further understand the content and characteristics of the present invention, the following embodiments are given as examples, and detailed descriptions are as follows in conjunction with the accompanying drawings.

如图1所示,本发明实施例的膨胀土边坡浅层破坏土体抗剪强度试验方法包括:As shown in Figure 1, the expansive soil slope shallow layer failure soil shear strength test method of the embodiment of the present invention comprises:

S101、试样制作,采用环刀削取原状土样,切削时保证试样与环刀壁贴合紧密;平行试验试样的密度差和含水率差分别不大于±0.1g/cm3和1%;S101. Sample preparation, using a ring cutter to cut the undisturbed soil sample, and ensure that the sample is closely attached to the wall of the ring cutter when cutting; the density difference and moisture content difference of the parallel test samples are not greater than ±0.1g/cm 3 and 1 %;

S102、对试样进行有荷作用干湿循环;S102, performing a dry-wet cycle on the sample under load;

S103、干湿循环饱和试样在相应垂直压力下饱和固结;S103, the dry-wet cycle saturated sample is saturated and consolidated under the corresponding vertical pressure;

S104、根据实际抗剪强度大小选择测力环,启动直剪仪,以恒定速度进行剪切,直至获得峰值抗剪强度;S104. Select the force measuring ring according to the actual shear strength, start the direct shear instrument, and perform shearing at a constant speed until the peak shear strength is obtained;

S105、采用改进的幂函数对试验数据进行拟合。S105, using an improved power function to fit the test data.

进一步,步骤S102所述的对试样进行有荷作用干湿循环的具体方法为:Further, the specific method of carrying out the dry-wet cycle with load on the sample described in step S102 is as follows:

将试样在真空饱和器内抽真空饱和,此时限制试样膨胀,保持体积恒定,真空饱和完成后,再施加与法向应力等效的荷载浸水饱和96h;然后,将充分吸水膨胀饱和试样置于40℃鼓风干燥烘箱中干燥36h,使饱和试样干燥至恒重;重复上述两个步骤多次,直至达到预定的干湿循环次数。Vacuum and saturate the sample in the vacuum saturator. At this time, limit the expansion of the sample and keep the volume constant. After the vacuum saturation is completed, apply a load equivalent to the normal stress and soak in water for 96 hours; Place the sample in a blast drying oven at 40°C for 36 hours to dry the saturated sample to constant weight; repeat the above two steps several times until the predetermined number of drying and wetting cycles is reached.

进一步,步骤S102中所述的法向应力为5kPa、15kPa、30kPa、50kPa、100kPa、200kPa和300kPa;预定的干湿循环次数,根据实际情况取4~8次。Further, the normal stress described in step S102 is 5kPa, 15kPa, 30kPa, 50kPa, 100kPa, 200kPa and 300kPa; the predetermined number of dry-wet cycles is 4-8 according to the actual situation.

进一步,步骤S103中所述试样饱和固结条件为试样的垂直变形等于或小于0.003mm/h。Further, the saturated consolidation condition of the sample in step S103 is that the vertical deformation of the sample is equal to or less than 0.003 mm/h.

进一步,步骤S104中所述测力环选择是当垂直压力为5kPa、15kPa和30kPa时,选择的测力环最大量程为0.1kN,精度为0.0025kN;其它各垂直压力抗剪强度测试时采用规范常用测力环;恒定速度为0.01mm/h,以保证试样为排水剪切条件,也可根据膨胀土粘粒含量及胀缩等级选择更小值。Further, the selection of the force measuring ring in step S104 is that when the vertical pressure is 5kPa, 15kPa and 30kPa, the maximum range of the selected force measuring ring is 0.1kN, and the accuracy is 0.0025kN; The force measuring ring is commonly used; the constant speed is 0.01mm/h to ensure that the sample is under drainage and shear conditions, and a smaller value can also be selected according to the clay content of expansive soil and the degree of expansion and contraction.

进一步,步骤S105中所述改进幂函数为实际操作为将试验测试结果输入origin软件中,自定义上述改进幂函数,以有效法向应力σ为横坐标,抗剪强度τ为纵坐标,采用最小二乘法进行拟合,获得(A,n,T)三参数。Further, the improved power function described in step S105 is The actual operation is to input the test results into the origin software, customize the above-mentioned improved power function, take the effective normal stress σ as the abscissa, and the shear strength τ as the ordinate, and use the least square method for fitting to obtain (A, n , T) three parameters.

式中:τ是抗剪强度;σ是有效法向应力;Pa是大气压力;(A,n,T)是拟合参数。where: τ is the shear strength; σ is the effective normal stress; P a is the atmospheric pressure; (A, n, T) is the fitting parameter.

进一步,采用极限平衡法分析边坡稳定性,运用geoslope软件自带的非线性强度参数分析功能基于以下两式,获得不同有效法向应力下不同条块土体抗剪强度参数的有效粘聚力c和有效摩擦角Furthermore, the limit equilibrium method is used to analyze the slope stability, and the nonlinear strength parameter analysis function of the geoslope software is used to obtain the effective cohesion of the shear strength parameters of different strips of soil under different effective normal stresses based on the following two formulas c and effective friction angle :

cc == PP aa AA (( σσ PP aa ++ TT )) nno -- σσ ×× AA nno (( σσ // PP aa ++ TT )) (( 11 -- nno )) == AA [[ (( 11 -- nno )) σσ ++ PP aa TT ]] (( σσ // PP aa ++ TT )) (( 11 -- nno ))

式中:c是有效粘聚力;是有效摩擦角;σ是有效法向应力;Pa是大气压力;(A,n,T)是拟合参数。In the formula: c is the effective cohesion; is the effective friction angle; σ is the effective normal stress; P a is the atmospheric pressure; (A, n, T) is the fitting parameter.

经大气干湿循环作用,天然、未经处治或处治不当的新开挖膨胀土边坡,往往在降雨期间或降雨后发生浅层破坏,此时边坡浅层土体可处于饱和或近似饱和状态,破坏时滑动面土体实际受到的有效法向应力小,位于10~30kPa之间。在这种情况下,标准慢剪强度试验方法采用50~300kPa或100~400kPa的4级法向应力与边坡破坏时滑面土体的实际受力状态不相符。由此,本发明实施例在原有4级法向应力的基础上增加3级低法向应力,以模拟边坡破坏时土体的实际受力状态。Due to the dry-wet cycle of the atmosphere, the natural, untreated or improperly treated expansive soil slopes often have shallow damage during or after the rainfall. At this time, the shallow soil of the slope may be saturated or nearly saturated. state, the effective normal stress actually received by the soil on the sliding surface is small at the time of failure, which is between 10 and 30kPa. In this case, the standard slow shear strength test method adopts the 4-level normal stress of 50-300kPa or 100-400kPa, which is inconsistent with the actual stress state of the sliding surface soil when the slope fails. Therefore, the embodiment of the present invention adds 3 levels of low normal stress to the original 4 levels of normal stress to simulate the actual stress state of the soil when the slope is damaged.

本发明的膨胀土边坡浅层破坏土体抗剪强度试验方法有效法向应力包含反映土体实际受力状态的较低有效法向应力;考虑了大气干湿循环作用,且干湿循环膨胀过程中施加与剪切时法向应力相一致的等效荷载作用;抗剪强度试验结果采用改进的幂函数代替摩尔库伦线性函数进行拟合。The effective normal stress of the test method for the shear strength of expansive soil slope shallow layer damaged soil of the present invention includes a lower effective normal stress reflecting the actual stress state of the soil; the effect of atmospheric dry-wet cycle is considered, and the dry-wet cycle expands During the process, an equivalent load consistent with the normal stress during shearing is applied; the results of the shear strength test are fitted with an improved power function instead of the Mohr-Coulomb linear function.

表1是本发明实施例的抗剪强度实验数据拟合结果。Table 1 is the fitting result of the shear strength experimental data of the embodiment of the present invention.

表1Table 1

由表1和图2知,高法向应力的抗剪强度随有荷作用干湿循环次4次后基本趋于稳定,而低法向应力条件下的值仍不断减小,在作用8次后法向应力为零时的抗剪强度值趋于零。低法向应力条件下,规范直线法拟合的结果显著大于实测值,而改进幂函数法拟合结果与实测值相差较小,能真实的反映膨胀土边坡发生浅层破坏时滑面土体的真实强度。因此,需测试含低有效法向应力的慢剪强度,同时考虑有荷作用干湿循环的影响,并运用改进幂函数对测试结果进行拟合。采用此类抗剪强度参数并结合极限平衡法开展膨胀土边坡稳定性分析能获得与边坡浅层破坏相一致的结论。It can be known from Table 1 and Figure 2 that the shear strength with high normal stress basically tends to be stable after 4 dry-wet cycles under load, while the value under low normal stress continues to decrease. The shear strength value tends to zero when the back normal stress is zero. Under the condition of low normal stress, the fitting result of the standard straight line method is significantly greater than the measured value, while the fitting result of the improved power function method is slightly different from the measured value, which can truly reflect the failure of the expansive soil slope when the shallow layer is damaged. the actual strength of the body. Therefore, it is necessary to test the slow shear strength with low effective normal stress, and at the same time consider the influence of dry-wet cycle under load, and use the improved power function to fit the test results. Using such shear strength parameters combined with the limit equilibrium method to carry out stability analysis of expansive soil slopes can obtain conclusions consistent with shallow slope failures.

以上所述仅是对本发明的较佳实施例而已,并非对本发明作任何形式上的限制,凡是依据本发明的技术实质对以上实施例所做的任何简单修改,等同变化与修饰,均属于本发明技术方案的范围内。The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Any simple modifications made to the above embodiments according to the technical essence of the present invention, equivalent changes and modifications, all belong to this invention. within the scope of the technical solution of the invention.

Claims (7)

1.一种膨胀土边坡浅层破坏土体抗剪强度试验方法,其特征在于,所述膨胀土边坡浅层破坏土体抗剪强度试验方法包括:1. a kind of expansive soil slope shallow layer failure soil body shear strength test method, it is characterized in that, described expansive soil slope shallow layer damage soil body shear strength test method comprises: 步骤一、试样制作,采用环刀削取原状土样,切削时保证试样与环刀壁贴合紧密;平行试验试样的密度差和含水率差分别不大于±0.1g/cm3和1%;Step 1. Sample preparation. Cut the undisturbed soil sample with a ring knife, and ensure that the sample is closely attached to the wall of the ring knife during cutting; the density difference and moisture content difference of the parallel test samples are not greater than ±0.1g/ cm3 and 1%; 步骤二、对试样进行有荷作用干湿循环;Step 2, carry out dry-wet cycle on the sample under load; 步骤三、干湿循环饱和试样在相应垂直压力下饱和固结;Step 3, the dry-wet cycle saturated sample is saturated and consolidated under the corresponding vertical pressure; 步骤四、根据实际抗剪强度大小选择测力环,启动直剪仪,以恒定速度进行剪切,直至获得峰值抗剪强度;Step 4. Select the force measuring ring according to the actual shear strength, start the direct shear instrument, and shear at a constant speed until the peak shear strength is obtained; 步骤五、采用改进的幂函数对试验数据进行拟合。Step 5, using the improved power function to fit the experimental data. 2.如权利要求1所述的膨胀土边坡浅层破坏土体抗剪强度试验方法,其特征在于,步骤二所述的对试样进行有荷作用干湿循环的具体方法为:2. expansive soil slope shallow layer failure soil shear strength test method as claimed in claim 1, is characterized in that, the concrete method that the sample described in step 2 is carried out to dry-wet cycle with load is: 将试样在真空饱和器内抽真空饱和,再施加与法向应力等效的荷载浸水饱和96h;然后,将充分吸水膨胀饱和试样置于40℃鼓风干燥烘箱中干燥36h,使饱和试样干燥至恒重;重复上述两个步骤多次,直至达到预定的干湿循环次数。Vacuum and saturate the sample in a vacuum saturator, then apply a load equivalent to the normal stress and immerse in water for 96 hours; then, place the fully water-swelled and saturated sample in a blast drying oven at 40°C for 36 hours to make the saturated test The sample was dried to constant weight; the above two steps were repeated several times until the predetermined number of drying and wetting cycles was reached. 3.如权利要求1所述的膨胀土边坡浅层破坏土体抗剪强度试验方法,其特征在于,步骤二中所述的法向应力为5kPa、15kPa、30kPa、50kPa、100kPa、200kPa、300kPa;预定的干湿循环次数,取4~8次。3. expansive soil slope shallow layer failure soil shear strength test method as claimed in claim 1, is characterized in that, the normal stress described in step 2 is 5kPa, 15kPa, 30kPa, 50kPa, 100kPa, 200kPa, 300kPa; the predetermined number of dry and wet cycles is 4 to 8 times. 4.如权利要求1所述的膨胀土边坡浅层破坏土体抗剪强度试验方法,其特征在于,步骤三中所述试样饱和固结条件为试样的垂直变形等于或小于0.003mm/h。4. expansive soil slope shallow layer failure soil shear strength test method as claimed in claim 1, is characterized in that, the sample saturation consolidation condition described in step 3 is that the vertical deformation of sample is equal to or less than 0.003mm /h. 5.如权利要求1所述的膨胀土边坡浅层破坏土体抗剪强度试验方法,其特征在于,步骤四中所述测力环选择是当垂直压力为5kPa、15kPa和30kPa时,选择的测力环最大量程为0.1kN,精度为0.0025kN。5. expansive soil slope shallow layer failure soil shear strength test method as claimed in claim 1, is characterized in that, the selection of force-measuring ring described in step 4 is when vertical pressure is 5kPa, 15kPa and 30kPa, selects The maximum measuring range of the force measuring ring is 0.1kN, and the precision is 0.0025kN. 6.如权利要求1所述的膨胀土边坡浅层破坏土体抗剪强度试验方法,其特征在于,步骤五中所述改进幂函数为以有效法向应力σ为横坐标,抗剪强度τ为纵坐标,采用最小二乘法进行拟合,获得(A,n,T)三参数。6. expansive soil slope shallow layer failure soil shear strength test method as claimed in claim 1, is characterized in that, the improved power function described in step 5 is Taking the effective normal stress σ as the abscissa and the shear strength τ as the ordinate, the least squares method is used for fitting, and the three parameters (A, n, T) are obtained. 式中:τ是抗剪强度;σ是有效法向应力;Pa是大气压力;(A,n,T)是拟合参数。where: τ is the shear strength; σ is the effective normal stress; P a is the atmospheric pressure; (A, n, T) is the fitting parameter. 7.如权利要求1所述的膨胀土边坡浅层破坏土体抗剪强度试验方法,其特征在于,获得不同有效法向应力下不同条块土体抗剪强度参数的有效粘聚力c和有效摩擦角 7. expansive soil slope shallow layer failure soil shear strength test method as claimed in claim 1, is characterized in that, obtains the effective cohesion c of different strip soil shear strength parameters under different effective normal stresses and the effective friction angle cc == PP aa AA (( σσ PP aa ++ TT )) nno -- σσ ×× AA nno (( σσ // PP aa ++ TT )) (( 11 -- nno )) == AA [[ (( 11 -- nno )) σσ ++ PP aa TT ]] (( σσ // PP aa ++ TT )) (( 11 -- nno )) 式中:c是有效粘聚力;是有效摩擦角;σ是有效法向应力;Pa是大气压力;(A,n,T)是拟合参数。In the formula: c is the effective cohesion; is the effective friction angle; σ is the effective normal stress; P a is the atmospheric pressure; (A, n, T) is the fitting parameter.
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Application publication date: 20151125