A method of determining macroscopic distribution of swelling rock / soil

Abstract

The present disclosure relates to a method for determining macroscopic distribution of swelling rock / soil, and the method provided by the present disclosure can divide the stratum distribution range controlled by different parent rock lithology of each stratum paragraph according to the spatial distribution characteristics of the sedimentary facies of different stratum paragraphs in the region to be studied and the parent rock lithology category, and determine the macroscopic distribution of swelling rock / soil according to the weathering degree and swelling characteristics of sandstone and mudstone of each stratum paragraph. The method provided by the present disclosure can determine the distribution position and swelling strength of the swelling rock / soil in the region, and the main distribution range of the swelling rock / soil can be circled through the research on the distribution characteristics of the swelling rock / soil in a large range, and then the exploration means can be reasonably arranged, and the engineering investigation cost can be reduced.

Description

Technical Field

[0001] This disclosure relates to the field of surveying and design technology for linear transportation engineering (railways, highways, etc.), and in particular to a method for determining the macroscopic distribution of expansive rock / soil. Background Technology

[0002] Expansive rocks (swelling rocks) refer to a type of rock containing a large amount of hydrophilic minerals. Due to physicochemical reactions with water, they undergo volume changes and generate significant internal stress when deformation is constrained. They are mainly silty sandstone and mudstone. Expansive soil (swelling soil) is a type of cohesive soil containing a large amount of hydrophilic clay minerals. It swells upon absorbing water, disintegrates or softens upon contact with water, shrinks upon losing water, and has poor erosion resistance. This type of soil with significant swelling and shrinkage properties is called expansive soil.

[0003] For railway and highway engineering projects, research on expansive rock / soil has focused primarily on its microscopic properties and subsequent remediation and construction methods, with limited attention paid to its macroscopic distribution patterns. Furthermore, in linear transportation engineering (railways, highways, etc.), the common practice for determining the presence of expansive rock / soil in the construction area is to conduct on-site inspections of the area ahead of construction. Only after detecting the presence of expansive rock / soil is a detour or remediation plan designed, which is costly and requires significant investment. If the macroscopic distribution of expansive rock / soil in the route area could be determined during the early site selection phase of linear transportation engineering, guiding the route design in the early stages of construction, construction costs could be reduced to some extent. Moreover, avoiding expansive rock / soil during route selection could further enhance the safety of the project's later operation.

[0004] Currently, the macroscopic spatial distribution patterns of expansive rocks / soils are mainly determined based on surface morphology and color. For example, in terms of surface morphology, expansive rocks / soils are mostly distributed on second- and higher terraces, piedmont hills, and basin edges, characterized by gentle slopes and the absence of obvious natural scarps. In terms of color, highly expansive rocks / soils are often predominantly grayish-white or grayish-green, moderately expansive rocks / soils are often brown, red, or gray, and weakly expansive rocks / soils are often yellowish-brown. Relying on empirical and qualitative methods based on surface morphology and color to identify expansive rocks / soils cannot accurately determine their distribution patterns and can only serve as supplementary methods.

[0005] Therefore, it is essential to provide a method that can accurately determine the spatial distribution of expansive rock / soil to guide the route selection of related linear traffic engineering projects, reduce engineering construction costs, and increase the safety of subsequent engineering operations. Summary of the Invention

[0006] To address the aforementioned technical problems, this disclosure provides a method for determining the macroscopic distribution of expansive rock / soil.

[0007] In a first aspect, this disclosure provides a method for determining the macroscopic distribution of expansive rock / soil, the method comprising the following steps:

[0008] (1) Determine the stratigraphic units in which mudstone is developed in the area to be studied, and divide the mudstone-developed strata into segments and the sedimentary facies of each segment.

[0009] (2) Samples were taken from multiple locations in each stratigraphic segment where mudstone was developed, and major and trace element analysis was performed on the samples to determine the lithological category of the source rock and to calculate the weathering index of sandstone and mudstone.

[0010] (3) Perform swelling tests on the samples from step (2) to determine the stratigraphic segments in which swelling rock / soil is developed;

[0011] (4) Based on the spatial distribution characteristics of sedimentary facies in different stratigraphic segments and the lithological categories of source rocks, the stratigraphic distribution range controlled by different source rocks in each stratigraphic segment is divided, and the macroscopic distribution range of expansive rocks / soils is determined based on the weathering degree and expansive characteristics of sandstone and mudstone in each stratigraphic segment.

[0012] The method disclosed herein can systematically analyze and determine the macroscopic spatial distribution law of expansive rocks / soils from aspects such as sedimentary facies characteristics, provenance characteristics, stratigraphic weathering characteristics, and expansibility characteristics of rocks / soils at different stratigraphic levels in the area under study. This method can guide the design of linear transportation engineering projects and reduce the construction cost of linear transportation engineering projects.

[0013] The linear transportation engineering described in this invention includes transportation engineering such as railways and highways.

[0014] As a preferred technical solution of this disclosure, the method for determining the stratigraphic unit of mudstone development in the area to be studied in step (1) includes: collecting geological map data of the area to be determined, and determining the geological map data based on the geological data, wherein the geological map data includes geological maps at a scale of 1:250,000, 1:200,000, and 1:50,000, or geological maps at a larger scale.

[0015] As a preferred technical solution of this disclosure, the classification of sedimentary facies in step (1) is based on rock assemblage characteristics, spatial location of sedimentation, and sedimentary microfacies.

[0016] As a preferred technical solution of this disclosure, the sedimentary facies include alluvial fan sediments, alluvial fan sediments, fluvial sediments, lacustrine sediments and marine sediments, preferably braided river facies sediments, braided river delta facies sediments and lacustrine sediments.

[0017] The sedimentary facies involved in different study areas can vary greatly. The main sedimentary facies include alluvial and diluvial fan deposits, fluvial deposits, lacustrine deposits, and marine deposits. Different sedimentary facies are further subdivided into sedimentary subfacies and sedimentary microfacies, etc.

[0018] As a preferred technical solution of this disclosure, the sampling points in step (2) include sampling points in the four directions of east, south, west and north.

[0019] As a preferred technical solution of this disclosure, the lithology of the sampling in step (2) includes siltstone, silty mudstone and mudstone.

[0020] When taking samples, sampling points in different study areas should cover the four directions of east, south, west, and north as much as possible. The spatial density of the samples should be appropriately adjusted according to the complexity of the sedimentary facies development. The more complex the sedimentary facies development, the greater the sampling density, and vice versa.

[0021] As a preferred technical solution of this disclosure, the method for determining the lithological category of the source rock includes: determining the lithology of the source area of ​​sandstone and mudstone source rocks by major elements, trace element Hf and La / Th, and trace element Co / Th and La / Sc, as follows:

[0022] (1) Determine the source lithology of sandstone and mudstone parent rocks by major elements. The determination criteria are as follows: Figure 1 As shown, for Figure 1 The calculation methods for F1 and F2 involved are as follows:

[0023] F1 = [F1'(TiO2) × sample(TiO2)] + [F1'(Al2O3) × sample(Al2O3)] + [F1'(Fe2O3) × sample(Fe2O3)] + [F1'(MgO) × sample(MgO)] + [F1'(CaO) × sample(CaO)] + [F1'(Na2O) × sample(Na2O)] + [F1'(K2O) × sample(K2O)] + C (constant);

[0024] F2 = [F2'(TiO2)×sample(TiO2)] + [F2'(Al2O3)×sample(Al2O3)] + [F2'(Fe2O3)×sample(Fe2O3)] + [F2'(MgO)×sample(MgO)] + [F2'(CaO)×sample(CaO)] + [F2'(Na2O)×sample(Na2O)] + [F2'(K2O)×sample(K2O)] + C (constant);

[0025] Wherein, sample (TiO2), sample (Al2O3), sample (Fe2O3), sample (MgO), sample (CaO), sample (Na2O), and sample (K2O) represent the percentage content of each major element;

[0026] The values ​​of F1' and F2' are shown in Table 1:

[0027] Table 1

[0028] variable <![CDATA[TiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> MgO CaO <![CDATA[Na2O]]> <![CDATA[K2O]]> C (constant) <![CDATA[F1']]> -1.773 -0.607 0.76 -1.5 0.616 0.509 -1.224 -9.090 <![CDATA[F2']]> 0.445 0.070 -0.25 -1.142 0.438 1.475 1.426 -6.816

[0029] (2) Trace element Hf and La / Th ratios are used to determine the provenance lithology of sandstone and mudstone parent rocks. The criteria are as follows: Figure 2 As shown;

[0030] (3) Trace element Co / Th and La / Sc ratios determine the lithology of the source rock of sandstone and mudstone parent rocks. The criteria are as follows: Figure 3 As shown, in Figure 3 The Archean, Proterozoic, and Phanerozoic eons in the text are all mineralization periods.

[0031] exist Figure 3 In geology, TTG refers to Trondhjemite, Tonalite, and Granodiorite, which are generally felsic rocks. Therefore, TTG is quite similar to felsic volcanic rocks in the Co / Th-La / Sc discrimination diagram.

[0032] As a preferred embodiment of this disclosure, the weathering degree of the sandstone and mudstone is represented by the CIA index, which is calculated using the formula shown in Equation I:

[0033] CIA=Al2O3 / [Al2O3+K2O+Na2O+CaO*]×100

[0034] Wherein, Al2O3, K2O, and Na2O refer to the mole fraction of the substance in the sample, and CaO* refers to the mole fraction of CaO in the silicate in the sample.

[0035] Calculating the weathering index (CIA) of sandstone and mudstone samples can determine whether there is a recycled source in the provenance area. A recycled source refers to the source provided by the re-uplift and erosion of early sedimentary strata. Recycled sources often have a high degree of weathering (most of the feldspar has been weathered and altered to form expansive minerals such as kaolinite and montmorillonite), and are therefore more likely to form expansive mudstone.

[0036] Secondly, this disclosure provides the application of the method described in the first aspect in the survey and design of linear traffic engineering projects.

[0037] The method disclosed herein can determine the distribution and degree of expansive rock / soil in the route area during the preliminary reconnaissance and survey stages of linear transportation engineering design. This can guide the large-scale route selection in the early stages of linear (railway, highway, etc.) transportation engineering, and also provide basic geological support for the preliminary investigation of regional industrial and civil building engineering. It can significantly reduce construction costs and increase the safety of later engineering operation.

[0038] The technical solution provided in this disclosure has the following advantages compared with the prior art:

[0039] (1) This disclosure realizes the method of determining the spatial distribution law of expansive rock / soil in the region by performing major and trace tests, sedimentary facies analysis and expansibility tests on a small number of samples;

[0040] (2) The method provided in this disclosure can determine the spatial distribution of expansive rock / soil in a region from a macroscopic perspective, which is of great significance for guiding the early planning of linear traffic projects, reasonable detours, and optimized route selection.

[0041] (3) The method provided in this disclosure is highly versatile and applicable to the determination of the spatial distribution pattern of expansive rocks / soils within all sedimentary basins, especially suitable for sedimentary basins where the source rocks are igneous rocks and metamorphic rocks. Attached Figure Description

[0042] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0043] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a diagram illustrating the analysis of the provenance lithology of sandstone and mudstone parent rocks based on major elements, as described in this disclosure.

[0045] Figure 2 This is a diagram illustrating the analysis of the provenance lithology of sandstone and mudstone parent rocks based on trace element Hf and La / Th ratios as described in this disclosure.

[0046] Figure 3 This is a lithological analysis diagram of the source region of sandstone and mudstone parent rocks determined by trace element Co / Th and La / Sc as described in this disclosure;

[0047] Figure 4 Geological data and research sampling maps of the Helan Mountain area provided in Embodiment 1 of this disclosure;

[0048] Figure 5 This is a spatial distribution diagram of the four sedimentary facies sections in the extended group of Example 1;

[0049] Figure 6 This is a spatial distribution diagram of the sedimentary facies of the five sections of the extended group in Example 1;

[0050] Figure 7 The results of major and trace element analysis of the sample Figure 1 (Discrimination diagram of property functions in clastic rock source areas);

[0051] Figure 8 The results of major and trace element analysis of the sample Figure 2 (La / Th-Hf discriminant plot);

[0052] Figure 9 The results of major and trace element analysis of the sample Figure 3 (Co / Th-La / Sc discriminant diagram);

[0053] Figure 10 This is a model diagram of the paleogeographic features and provenance of sections four and five of the extended group. Detailed Implementation

[0054] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0055] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0056] Example 1

[0057] This embodiment provides a method for determining the macroscopic distribution of expansive rocks / soils in the Upper Triassic Yanchang Formation within the Helan Mountain region. The study area is as follows: Figure 4 As shown.

[0058] According to geological data of the Helan Mountain area, the Upper Triassic Yanchang Formation in the Helan Mountain area can be divided into a total of 5 sections. The lithology of the first to fifth sections of the Yanchang Formation changes from coarse to fine from bottom to top. The main sedimentary facies of the first to third sections of the Yanchang Formation are alluvial fans and braided rivers. In the fourth and fifth sections of the Yanchang Formation, the sedimentary facies are mainly braided rivers, braided river deltas and lacustrine deposits.

[0059] The method includes the following steps:

[0060] (1) Segmentation and sedimentary facies division

[0061] Segmentation: Collect geological map data of 1:250,000, 1:200,000 and 1:50,000 scales for the Helan Mountain area. Based on the geological data, determine that the main stratigraphic units for mudstone development in the Helan Mountain area are the fourth and fifth members of the Yanchang Formation.

[0062] Sedimentary facies classification: Based on rock assemblage characteristics, spatial location of sediments, and sedimentary microfacies, the mudstone-developed strata of the fourth and fifth members of the Yanchang Formation were classified into sedimentary facies. According to the field stratigraphic rock assemblage characteristics, spatial location of sediments, and sedimentary microfacies of the fourth and fifth members of the Yanchang Formation, the sedimentary facies of the fourth member were determined to be braided river deltaic facies and lacustrine facies, while the sedimentary facies of the fifth member were mainly braided river facies, braided river deltaic facies, and lacustrine facies. The specific spatial distribution of sedimentary facies is as follows: Figure 5 , Figure 6 As shown;

[0063] (2) Sampling was conducted to determine the lithological type of the source rock and to calculate the weathering index of sandstone and mudstone.

[0064] Sampling: Multiple sampling sites were taken from the mudstone strata of the fourth and fifth members of the Yanchang Formation in the study area. Sampling points in different study areas were designed to cover all four cardinal directions (east, south, west, and north). The spatial density of the sampling was adjusted according to the complexity of the sedimentary facies development; the more complex the sedimentary facies development, the higher the sampling density, and vice versa. Sampling locations are as follows: Figure 4 As shown, the sampled lithology is mainly siltstone and mudstone;

[0065] Determine the lithological category of the source rock: Perform major and trace element analysis on the sample from step (3), calculate F1 and F2, La / Th, Co / Th and La / Sc. The results of the major and trace element analysis of the sample are shown in [reference needed]. Figure 7-9 ,Depend on Figure 7 and Figure 8 It can be seen that the source rocks of the fourth member of the Yanchang Formation are mainly quartzite, felsic rocks, and intermediate rocks, while the source rocks of the fifth member of the Yanchang Formation are mainly quartzite and mafic rocks; Figure 9 It can be seen that the age and lithology of the parent rocks of the fourth and fifth members of the Yanchang Formation tend to be TGG rocks and felsic volcanic rocks. The specific age of the parent rock bodies varies depending on the sampling location, and needs to be determined in conjunction with the rock bodies developed around the study area.

[0066] The Langshan area in the northwest of the Helan Mountains is mainly composed of the Paleoproterozoic Alashan Group and the Proterozoic Langshan Group, with lithology primarily consisting of garnet biotite plagioclase gneiss, biotite hornblende plagioclase gneiss, plagioclase amphibolite, and a small amount of marble interlayers. The northern part of the Helan Mountains is mainly composed of high-grade regional metamorphic rocks of the Paleoproterozoic amphibolite-granulite facies, namely the Khondalite series. Currently, the northeastern Yinshan, Daqingshan, and Wulashan areas of the Helan Mountains mainly expose the Khondalite series, high-grade metamorphic gneiss and basic gneiss, as well as dioritic gneiss and greenschist. The southern part of the Helan Mountains exposes mainly igneous and metamorphic rocks, including the Zhaochigou Group biotite plagioclase gneiss, biotite monzogranite gneiss, and Huangqikou granite. The eastern and western parts of the Helan Mountains are early sedimentary basins, with the main rock bodies being pre-Late Triassic sedimentary strata.

[0067] Based on the source rock type of sediments at different sampling locations and the exposure of surrounding rock masses, the paleogeographic features and source control ranges of the fourth and fifth members of the Yanchang Formation in the Helan Mountain area were divided, such as... Figure 10 As shown, the material transport and control range in four directions of the fourth and fifth sections of the Yanchang Formation in the Helan Mountain area was determined.

[0068] The CIA (Chemical Index of Aquatic and Mudstone) was calculated to determine whether a recycled source exists in the provenance area. If the weathering coefficient of some samples is generally high, a recycled source is likely to exist. For example, samples from Xiangchizigou, Gulaben, and Rujigou generally have high CIA indices. Combined with the outcropping of rock masses around the Helan Mountain area, the provenance in the east and west directions of the study area was finally determined to be a recycled source. Recycled sources often have a high degree of weathering (most of the feldspar has weathered and altered to form expansive minerals such as kaolinite and montmorillonite), and are more likely to form expansive mudstone.

[0069] (3) Expansibility testing to determine the main stratigraphic segments in which expansive rocks / soils are developed.

[0070] According to the Railway Engineering Geological Investigation Specification (TB 10012-2019), expansive rock refers to rock containing a large amount of hydrophilic minerals, which undergoes significant volume changes when the water content changes. Expansive soil refers to cohesive soil rich in hydrophilic minerals, exhibiting characteristics of significant swelling, softening, and disintegration upon water absorption, rapid shrinkage and cracking upon water loss, and cyclic deformation. The analysis of expansive soil is as follows:

[0071] The classification of expansive soil differs from that of expansive rock. The expansion potential is mainly determined by indicators such as free expansion rate, montmorillonite content, and cation exchange capacity. When the above two indicators are met, it is judged to be of that grade. The specific judgment criteria are shown in Table 1.

[0072] Table 1: Classification of Expansion Potential

[0073]

[0074] The analysis of the swelling rock is as follows:

[0075] 1) The experimental items for expanding rocks include conventional rock physics experiments, such as saturated water absorption rate, swelling force, swelling rate, and free swelling rate;

[0076] 2) The determination of expansive rock conforms to the provisions of Table 2. When two or more indicators meet the requirements, it can be determined as expansive rock.

[0077] Table 2: Criteria for Judging Indoor Tests of Expanding Rock

[0078]

[0079] Note:

[0080] 1. For rocks that are not easily disintegrated, the axial V should be taken. H or radial V D The largest value in the free expansion rate is used for determination;

[0081] 2. Easily disintegrating rocks should be crushed, screened through a 0.5mm sieve to remove coarse particles, and then tested in accordance with the test method for the free swelling rate of soil.

[0082] The above criteria can be used to determine the expansibility of a sample and identify expansible rock / soil.

[0083] (4) Based on the spatial distribution characteristics of sedimentary facies in different stratigraphic segments and the lithological categories of the source rocks, the stratigraphic distribution range controlled by different source rocks in each stratigraphic segment is divided, and the spatial distribution range of expansive rocks / soils is determined based on the weathering degree and expansive characteristics of sandstone and mudstone in each stratigraphic segment.

[0084] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0085] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for determining the macroscopic distribution of expansive rock / soil, characterized in that, The method includes the following steps: (1) Determine the stratigraphic units in which mudstone is developed in the area to be studied, and divide the mudstone strata into segments, and classify the sedimentary facies of each segment; wherein, the method for determining the stratigraphic units in which mudstone is developed in the area to be studied includes: collecting geological map data of the area to be determined, and determining the sedimentary facies based on the geological data, wherein the geological map data includes 1:250,000 geological maps, 1:200,000 geological maps and 1:50,000 geological maps, or geological maps of larger scale; the basis for the division of sedimentary facies includes rock assemblage characteristics, spatial location of sedimentation and sedimentary microfacies; (2) Samples were taken from multiple locations in each stratigraphic segment where mudstone was developed, and major and trace element analysis was performed on the samples to determine the lithological category of the source rock and to calculate the weathering index of sandstone and mudstone. The sampling points included sampling points in the four directions of east, south, west and north. The lithology of the samples included siltstone and mudstone. (3) Perform swelling tests on the samples from step (2) to determine the stratigraphic segment in which expansive rock / soil is developed; the discrimination index for expansive soil includes free swelling rate, montmorillonite content and cation exchange capacity; the discrimination index for expansive rock includes saturated water absorption rate, swelling force, swelling rate and free swelling rate. (4) Based on the spatial distribution characteristics of sedimentary facies in different stratigraphic sections and the lithological categories of source rocks, the stratigraphic distribution range controlled by different source rocks in each stratigraphic section is divided, and the macroscopic distribution of expansive rocks / soils is determined based on the weathering degree and expansive characteristics of sandstone and mudstone in each stratigraphic section.

2. The method according to claim 1, characterized in that, The degree of weathering of the sandstone and mudstone is expressed by the CIA index, which is calculated by the following formula: CIA=Al2O3 / [Al2O3+K2O+Na2O+CaO*]×100 Among them, Al2O3, K2O, and Na2O refer to the mole fraction of the substance in the sample, and CaO* refers to the mole fraction of CaO in the silicate in the sample.

3. The application of the method described in claim 1 or 2 in the survey and design of linear traffic engineering.

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