Method for determining cement modified soil replacement thickness of expansive soil slope

Abstract

The invention provides a method for determining the cement modified soil replacement thickness of an expansive soil side slope, and the method comprises the steps: determining the cement modified soil replacement thickness of the expansive soil side slope according to the direct influence depth of an atmospheric environment, a protection part correction value, a construction influence correction value, other factor correction values and an expansion coefficient value of a soil body of the expansive soil side slope; the influence on each factor is fully and comprehensively considered in the determination of the replacement thickness of the cement modified soil, the replacement thickness meets the actual demand, a valuing basis is provided for the replacement thickness of the cement modified soil of the expansive soil area slope engineering, technical support is provided for investigation and design of the expansive soil slope protection engineering, the working efficiency is improved, the cost is saved, and the economic benefit is increased. Spoil is reduced, and the long-term stability of the expansive soil slope and the reliability of engineering design are greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of engineering design and relates to a method for determining replacement thickness. Background Art

[0002] Expansive soils are widely distributed in my country. Expansive soils are rich in hydrophilic minerals, mainly montmorillonite. Repeated expansion and contraction will cause damage to the soil structure, and the mechanical strength will decrease. At the same time, hidden cracks are developed, and the crack surface is smooth, causing serious damage to shallow engineering structures such as water conservancy, roads, railways, and housing construction. The damage is often extensive and repeated. In a dry-wet cycle environment, the expansive soil slope will expand and contract, causing structural damage. If no protective treatment is done, a very gentle slope is required to maintain stability.

[0003] Reducing the influence of the external atmospheric environment on the moisture content of expansive soil is one of the control methods for the stability of expansive soil slopes. Among them, replacement treatment is the most commonly used technical method in slope and channel engineering in expansive soil areas. The key role of the expansive soil replacement layer is to reduce the water exchange between the expansive soil and the atmospheric environment. The excavated expansive soil is modified by adding cement on site. After a certain construction process, a water-stable material, namely cement-modified soil, whose strength, permeability and expansion and contraction meet the requirements of slope protection can be obtained. It can not only reduce engineering waste soil, but also greatly reduce the thickness of the protective layer, and improve the long-term stability and reliability of the engineering slope. In the replacement treatment of expansive soil slopes, the thickness of cement-modified soil perpendicular to the slope surface is the replacement thickness of cement-modified soil on the expansive soil slope. The factors affecting the replacement thickness of cement-modified soil include internal and external factors. The internal factors mainly include soil swelling potential, groundwater occurrence form and abundance, slope height, project importance, etc. The external factors mainly include water-wading conditions, construction level, and meteorological conditions. Among them, soil swelling potential and slope water-wading environment are two key factors, and the influence of other factors is relatively small and uncertain. However, the current determination of the replacement thickness of cement-modified soil on expansive soil slopes does not adequately consider the influence of various factors, resulting in the replacement thickness not meeting actual needs, and the long-term stability of the expansive soil slope and the reliability of engineering design are low. Summary of the invention

[0004] In order to solve the problems that the influence of various factors is not sufficiently considered in determining the replacement thickness of cement-modified soil for expansive soil slopes described in the background technology, resulting in the replacement thickness not meeting actual requirements, and the long-term stability of the expansive soil slopes and the low reliability of engineering design, the present invention provides a method for determining the replacement thickness of cement-modified soil for expansive soil slopes.

[0005] The technical solution of the present invention includes:

[0006] According to the depth of the atmospheric influence zone in the area where the expansive soil slope is located, determine the depth of the atmospheric environment that can directly affect the expansive soil slope;

[0007] The working environment of the expansive soil slope protection part is divided into wading slope and non-wading slope, and the working environment factors of the wading slope and non-wading slope are corrected to obtain the correction value of the protection part;

[0008] Combined with the construction organization plan of the expansive soil slope, the construction technology guarantee capability and the weather influence during the construction period, the construction impact correction is carried out to obtain the construction impact correction value;

[0009] Based on the importance of the project, the height of the slope, the fluctuation range of the surface water level, and the hydrogeological conditions of the slope, other factors are corrected to obtain the correction values ​​of other factors;

[0010] The thickness of cement-modified soil replacement for the expansive soil slope is determined based on the depth directly affected by the atmospheric environment, the correction value for protected areas, the correction value for construction impact, the correction value for other factors, and the expansion coefficient of the expansive soil slope.

[0011] Furthermore, the depth d of the atmospheric influence zone a It refers to the depth of the atmospheric influence zone where the moisture content of expansive soil changes significantly periodically due to factors such as precipitation infiltration, evaporation, and capillary water action of groundwater in the expansive soil under the influence of natural climate. a Calculated from the natural ground or the outdoor design excavation surface of the building; the depth of the atmospheric influence zone is d a The basis for taking the value includes: observation data on the moisture content of underground expansive soil, ground temperature observation data, observation results of the structure of expansive soil in the excavated exploration pit changing with depth, local meteorological conditions, soil expansion grade, as well as past research results and past engineering experience.

[0012] Furthermore, the atmospheric environment can directly affect the depth d k It refers to the depth at which the atmospheric environment can affect the moisture content of the newly excavated expansive soil slope, which is related to the local precipitation characteristics, air humidity, sunshine and the properties of the expansive soil itself; the atmospheric environment can directly affect the depth d k Less than the atmospheric influence depth d a , the atmospheric environment can directly affect the depth d k is the depth of the atmospheric influence zone d a 20% of.

[0013] Furthermore, the protection part correction value is taken as follows: the protection part correction value k of the wading slope g =0.5m; Correction value k for the protection part of non-wading slope g =0.

[0014] Furthermore, the construction impact correction value k sThe value is 0-0.5m; when the thickness of cement modified soil replacement filling T of the expansive soil slope is less than 1.0m, the correction value k needs to be affected by construction. s Correct the replacement thickness of cement-modified soil on expansive soil slopes to achieve a replacement thickness of cement-modified soil on expansive soil slopes of T ≥ 1.0m.

[0015] Furthermore, the free expansion rate of the expansive soil slope is determined by sampling the expansive soil on site for testing; the expansion coefficient value δ' ef The value of is: when the free expansion rate of the expansive soil slope is: 40%<δ ef When <65%, δ' ef Take 60%; when the free expansion rate of the expansive soil slope is: 65% ≤ δ ef When <90%, δ' ef Take the value as 80%; when the free expansion rate of the expansive soil slope is: δ ef ≥90%, δ' ef The value is 105%.

[0016] Furthermore, the formula for determining the thickness of the cement-modified soil replacement fill for the expansive soil slope is:

[0017] T=d k +2.0(δ' ef -60%)+k g +k s +k x ,

[0018] Where, T is the thickness of cement modified soil protective layer; d k The atmospheric environment can directly affect the depth; δ' ef is the expansion coefficient value; k g k is the correction value of the protected part; s k is the correction value for construction impact; x Correct values ​​for other factors.

[0019] Compared with the prior art, the present invention determines the replacement thickness of cement modified soil for expansive soil slopes according to the depth directly affected by the atmospheric environment, the correction value of the protected part, the correction value of the construction impact, the correction value of other factors and the expansion coefficient value of the soil body of the expansive soil slope. The influence of various factors is fully and comprehensively considered in determining the replacement thickness of cement modified soil, and the replacement thickness meets actual needs. A basis for selecting the replacement thickness of cement modified soil for slope projects in expansive soil areas is provided, technical support is provided for the survey and design of expansive soil slope protection projects, work efficiency is improved, costs are saved, abandoned soil is reduced, and the long-term stability of the expansive soil slope and the reliability of engineering design are greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0021] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0022] A method for determining the thickness of cement-modified soil replacement for expansive soil slopes, the flow chart is as follows: Figure 1 The specific steps are as follows.

[0023] Through geological survey of expansive soil slopes, based on local meteorological conditions such as rainfall and rainfall intensity, air humidity, number of sunshine days, etc., soil expansion grade, slope parameters and operating environment, the relevant influencing factors of cement modified soil replacement thickness are determined, mainly including: the atmospheric environment of the expansive soil slope can directly affect the depth, the working environment of the protection part of the expansive soil slope, the construction impact of the expansive soil slope, the expansion coefficient value of the soil of the expansive soil slope and the influence of other factors.

[0024] Therefore, in the present invention, the depth of the atmospheric environment that can directly affect the expansive soil slope is first determined based on the depth of the atmospheric influence zone in the area where the expansive soil slope is located.

[0025] Specifically, the depth of the atmospheric influence zone d a It refers to the depth of the atmospheric influence zone where the moisture content of expansive soil changes significantly periodically due to factors such as precipitation infiltration, evaporation, and capillary water action of groundwater in the expansive soil under the influence of natural climate. a Starting from the natural ground or the outdoor designed excavation surface of the building.

[0026] Depth of atmospheric influence zone d a The basis for taking the value includes: observation data on the moisture content of underground expansive soil, ground temperature observation data, observation results of the structure of expansive soil in the excavated exploration pit changing with depth, local meteorological conditions, soil expansion grade, as well as past research results and past engineering experience.

[0027] Depth of atmospheric influence zone d a Generally, it is 2.0-3.5m. When designing temporary protection projects, the depth of the atmospheric impact layer can be used, that is, the depth where the atmospheric impact is particularly significant, generally the depth of the atmospheric impact zone d a 30% of.

[0028] Specifically, the atmospheric environment can directly affect the depth d k It refers to the depth at which the atmospheric environment can affect the moisture content of a newly excavated expansive soil slope, which is related to the local precipitation characteristics, air humidity, sunshine and the properties of the expansive soil itself.

[0029] The atmospheric environment can directly affect the depth d k Less than the atmospheric influence depth d a , the atmospheric environment can directly affect the depth d k is the depth of the atmospheric influence zone d a 20% of.

[0030] For example, the atmospheric environment of the Middle Pleistocene expansive soils in Hubei and Henan, my country, can directly affect the depth d k Generally 0.5-0.6m.

[0031] Then, the working environment of the protection part of the expansive soil slope is divided into wading slope and non-wading slope, and the working environment factors of the wading slope and non-wading slope are corrected to obtain the correction value of the protection part.

[0032] Specifically, the protection position correction value k of the wading slope is g =0.5m; Correction value k for the protection part of non-wading slope g =0.

[0033] Then, combined with the construction organization plan of the expansive soil slope, the construction technology guarantee capability and the weather influence during the construction period, the construction impact correction is carried out to obtain the construction impact correction value.

[0034] Construction impact correction value k s The value is generally 0-0.5m. Due to the requirements of the existing mainstream construction machinery, when the thickness of cement modified soil replacement of the expansive soil slope is T<1.0m, the construction impact correction value k is required. s Correct the replacement thickness of cement-modified soil on expansive soil slopes to achieve a replacement thickness of cement-modified soil on expansive soil slopes of T ≥ 1.0m.

[0035] Then, other factors are corrected based on the importance of the project, slope height, fluctuation amplitude of the surface water level, and hydrogeological conditions of the slope to obtain correction values ​​of other factors.

[0036] Specifically, other factors correction value k x The general value range is -0.30-0.3m.

[0037] The thickness of cement-modified soil replacement for the expansive soil slope is determined based on the depth directly affected by the atmospheric environment, the correction value for protected areas, the correction value for construction impact, the correction value for other factors, and the expansion coefficient of the expansive soil slope.

[0038] Specifically, the formula for determining the thickness of cement-modified soil replacement for expansive soil slope is:

[0039] T=d k +2.0(δ' ef -60%)+kg +k s +k x ,

[0040] Where, T is the thickness of cement modified soil protective layer; d k The atmospheric environment can directly affect the depth; δ' ef is the expansion coefficient value; k g k is the correction value of the protected part; s k is the correction value for construction impact; x Correct values ​​for other factors.

[0041] Expansion coefficient value δ' ef The value of is: when the free expansion rate of the expansive soil slope is: 40%<δ ef When <65%, δ' ef Take 60%; when the free expansion rate of the expansive soil slope is: 65% ≤ δ ef When <90%, δ' ef Take the value as 80%; when the free expansion rate of the expansive soil slope is: δ ef ≥90%, δ' ef The value is 105%.

[0042] More specifically, the free expansion ratio is determined by testing expansive soils sampled on site.

[0043] Example

[0044] The present invention is used to determine the replacement thickness of cement-modified soil on the expansive soil channel slope, as described in detail below.

[0045] The free expansion rate test was carried out by sampling on site, and the weak expansion channel slope δ was determined according to the “1 / 3 judgment principle”. ef =58%; medium expansion channel slope δ ef =81%; strong expansion channel slopeδ ef =100%.

[0046] According to engineering experience, the depth of the atmospheric influence zone in Hubei and Henan provinces is generally 2.5-3.0m. Through actual field observations, it is determined that the atmospheric environment can directly affect the depth d k =0.6m.

[0047] Correction value k for the protection part of the water-passing section below the first-level bridleway g =0.5m; Correction value k for non-water-passing section protection above the first-level bridleway g =0.

[0048] The construction plan has been repeatedly verified, special mechanical equipment is configured on site, and a rainy day response plan is formulated to ensure the construction quality. sTake 0. Since construction machinery requires the site width to be no less than 1m, for the non-water-passing section slope of weak expansive soil, k s Take 0.4;

[0049] Combined with the importance of the project, the height of the slope, the fluctuation range of the surface water level, and the hydrogeological conditions of the slope, the correction value k of other factors is obtained. x =0.

[0050] According to the formula for determining the thickness of cement modified soil replacement for expansive soil slope: T = d k +2.0(δ' ef -60%)+k g +k s +k x , we can know that:

[0051] For non-water-passing section slopes:

[0052] The thickness of cement modified soil replacement for weak expansive soil channel slope is T = 0.6 + 2.0 (60% - 60%) + 0 + 0.4 + 0 = 1.0m;

[0053] The thickness of cement modified soil replacement for medium expansive soil channel slope is T = 0.6 + 2.0 (80% - 60%) + 0 + 0 + 0 = 1.0m;

[0054] Thickness of cement modified soil replacement for strong expansive soil channel slope T = 0.6 + 2.0 (105% - 60%) + 0 + 0 + 0 = 1.5m;

[0055] For the water-passing section slope:

[0056] The thickness of cement modified soil replacement for weak expansive soil channel slope is T = 0.6 + 2.0 (60% - 60%) + 0.5 + 0 + 0 = 1.1m;

[0057] The thickness of cement modified soil replacement for medium expansive soil channel slope is T = 0.6 + 2.0 (80% - 60%) + 0.5 + 0 + 0 = 1.5m;

[0058] The thickness of cement-modified soil replacement for the strongly expansive soil channel slope is T=0.6+2.0(105%-60%)+0.5+0+0=2.0m.

[0059] The thickness of the mud-modified soil replacement determined by the method of the present invention is shown in Table 1. In the preliminary design of the expansive soil channel slope, various factors are comprehensively considered in combination with soil expansibility, field tests, indoor tests, field observations, etc., and the cement-modified soil replacement thickness finally adopted is basically consistent with Table 1.

[0060] Table 1 Calculation statistics of cement modified soil replacement thickness

[0061]

[0062] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for determining the thickness of cement-modified soil replacement for an expansive soil slope, characterized in that: include: According to the depth of the atmospheric influence zone in the area where the expansive soil slope is located, determine the depth of the atmospheric environment that can directly affect the expansive soil slope; The working environment of the expansive soil slope protection part is divided into wading slope and non-wading slope, and the working environment factors of the wading slope and non-wading slope are corrected to obtain the correction value of the protection part; Combined with the construction organization plan of the expansive soil slope, the construction technology guarantee capability and the weather influence during the construction period, the construction impact correction is carried out to obtain the construction impact correction value; Based on the importance of the project, the height of the slope, the fluctuation range of the surface water level, and the hydrogeological conditions of the slope, other factors are corrected to obtain the correction values ​​of other factors; According to the free expansion rate of the expansive soil slope, the expansion coefficient value of the expansive soil slope is determined; The thickness of cement-modified soil replacement for the expansive soil slope is determined based on the depth directly affected by the atmospheric environment, the correction value for protected areas, the correction value for construction impact, the correction value for other factors, and the expansion coefficient of the expansive soil slope.

2. The method for determining the thickness of cement-modified soil replacement for an expansive soil slope according to claim 1, characterized in that: The depth of the atmospheric influence zone d a It refers to the depth of the atmospheric influence zone where the moisture content of expansive soil changes significantly periodically due to factors such as precipitation infiltration, evaporation, and capillary water action of groundwater in the expansive soil under the influence of natural climate. a Calculated from the natural ground or the outdoor designed excavation surface of the building; Depth of atmospheric influence zone d a The basis for taking the value includes: observation data on the moisture content of underground expansive soil, ground temperature observation data, observation results of the structure of expansive soil in the excavated exploration pit changing with depth, local meteorological conditions, soil expansion grade, as well as past research results and past engineering experience.

3. The method for determining the thickness of cement-modified soil replacement for an expansive soil slope according to claim 2, characterized in that: The atmospheric environment can directly affect the depth d k It refers to the depth at which the atmospheric environment can affect the moisture content in the newly excavated expansive soil slope, which is related to the local precipitation characteristics, air humidity, sunshine and the properties of the expansive soil itself. The atmospheric environment can directly affect the depth d k Less than the atmospheric influence depth d a , is the depth of the atmospheric influence zone d a 20% of.

4. The method for determining the thickness of cement-modified soil replacement for an expansive soil slope according to claim 3, characterized in that: The protection position correction value is: the protection position correction value k of the wading slope g =0.5m; Correction value k for the protection part of non-wading slope g =0.

5. The method for determining the thickness of cement-modified soil replacement for an expansive soil slope according to claim 4, characterized in that: The construction impact correction value k s The value is 0-0.5m; when the thickness of cement modified soil replacement filling T of the expansive soil slope is less than 1.0m, the correction value k needs to be affected by construction. s Correct the replacement thickness of cement-modified soil on expansive soil slopes to achieve a replacement thickness of cement-modified soil on expansive soil slopes of T ≥ 1.0m.

6. The method for determining the thickness of cement-modified soil replacement for an expansive soil slope according to claim 5, characterized in that: The free expansion rate of the expansive soil slope is determined by testing the expansive soil by sampling on-site; The expansion coefficient value δ' ef The value of is: when the free expansion rate of the expansive soil slope is: 40%<δ ef When <65%, δ' ef Take 60%; when the free expansion rate of the expansive soil slope is: 65% ≤ δ ef When <90%, δ' ef Take the value as 80%; when the free expansion rate of the expansive soil slope is: δ ef ≥90%, δ' ef The value is 105%.

7. A method for determining the thickness of cement-modified soil replacement for an expansive soil slope according to any one of claims 1 to 6, characterized in that: The formula for determining the thickness of the cement-modified soil replacement fill for the expansive soil slope is: T=d k +2.0(δ’ ef -60%)+k g +k s +k x , Where, T is the thickness of cement modified soil protective layer; d k The atmospheric environment can directly affect the depth; δ' ef is the expansion coefficient value; k g k is the correction value of the protected part; s k is the correction value for construction impact; x Correct values ​​for other factors.

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