Study of factors affecting the remediation of contaminated soil through pneumatic fracturing and soil vapor extraction.

In low-permeability soils, the effectiveness of soil vapor extraction (SVE) is often constrained, resulting in increased time and operational expenses. In this study, pneumatic fracturing and the SVE were combined to remediate low-permeability clay contaminated with ammonia gas. The soil parameters, pneumatic fracturing parameters, extraction mode, and other influencing factors were investigated via laboratory testing. The results indicated that: (1) Pneumatically induced fracturing disrupts soil structure, forming cracks and providing new pathways for ammonium gas migration; (2) the soil crack area exhibits a quadratic function relationship with both the fracturing pressure and frequency, and the soil crack area increases with higher pneumatic frequencies, leading to a faster pneumatic pressure decline; (3) a denser network of pathways emerges within the soil due to the reduced distance between the two pneumatic fracturing points, consequently enhancing soil permeability and increasing pollutant elimination efficiency; (4) the ammonium gas removal efficiency gradually increases with an increase in the extracted vapor flow rate, but there is an optimal extraction flow rate (9 L/min); (5) continuous extraction combined with gas injection effectively ameliorates the issue of prolonged fluctuations in ammonium gas concentration during the later stages of extraction. (6) Fracturing and extraction reduce the moisture content of the surrounding soil. The results demonstrated the feasibility and superiority of pneumatic pre-fracturing extraction in low-permeability soils.

Study on the deformation law of the construction of the cutoff wall of the reservoir.

Relying on the middle line of south-to-north water diversion project ning storage reservoir has built the construction load impact assessment project, the study through the analysis of field conditions select reasonable monitoring section and monitoring scheme, the late monitoring, the results can reflect the overall deformation of the wall and stress, and use in advance in the wall, monitoring instruments, to the typical section of field deformation, pressure, strain and stress, automatic oblique monitoring results to introduce the stress strain of the whole wall. Research results: The soil pressure showed the larger on the outside and the slightly smaller on the inside; Concrete strain relative to the initial state in the direction of vertical wall and vertical strain increment is larger, The strain increment along the wall direction is small; The data of the reinforcement stress gauge are all negative, And the quantity value of the inner steel bar gauge continues to increase, The monitoring value of the outer steel bar gauge has a tendency to decrease gradually; Small displacement of the plastic concrete walls, Large displacement of reinforced concrete walls, And the value along the wall for the small law; The inclination displacement value of monitoring section 2-2 and 3-3 gradually decreases with the continuous construction, The displacement value of monitoring 1-1 section also becomes smaller in the first and middle stages of construction, But in the late construction, This shows that the horizontal displacement of the monitoring 1-1 section in the later construction period has a recovery trend; The top settlement value is larger at the 1st-3rd wall, About 6 mm-10mm, The 4-6 pin is smaller, About 4 mm-5mm, Article 7-10, the pin is directly crushed by the vehicle, Its value is approximately 6 mm-8mm.

Multi-scale analysis of the mechanism of microbially induced calcium carbonate precipitation consolidation loess.

Microbial-induced calcium carbonate precipitation (MICP) treatment of consolidated loess has the advantages of high efficiency and environmental protection. In this study, changes in the microscopic pore structure of loess before and after MICP treatment were compared and quantified, combined with test results at different scales, to better understand the mechanisms of MICP-consolidated loess. The unconfined compressive strength (UCS) of MICP-consolidated loess is significantly increased, and the stress-strain curve indicates improved strength and stability of the loess. X-ray diffraction (XRD) test results show that the signal strength of calcium carbonate crystals is significantly enhanced after loess consolidation. The microstructure of the loess was determined by scanning electron microscopy (SEM). The loess SEM microstructure images are quantitatively analyzed using comprehensive image processing methods (including gamma adjustment, grayscale threshold selection, median processing). The changes in microscopic pore area and average pore sizes (Feret diameter) of the loess before and after consolidation are described. More than 95% of the pores consist of pores with a pore area of less than 100 µm2 and an average pore size of less than 20 µm. The total percentage of pore numbers with pore areas of 100-200 and 200-1000 µm2 decreased by 1.15% after MICP consolidation, while those with 0-1 and 1-100 µm2 increased. The percentage of pore numbers with an average pore size greater than 20 µm decreased by 0.93%, while the 0-1, 1-10, and 10-20 µm increased. Particle size distributions revealed a significant increase in particle size after MICP consolidation, with an increase of 89 µm in D50.

Experimental Study on Silt Soil Improved by Microbial Solidification with the Use of Lignin.

At present, in the field of geotechnical engineering and agricultural production, with increasingly serious pollution an environmentally friendly and efficient means is urgently needed to improve the soil mass. This paper mainly studied the microbial induced calcium carbonate precipitation (MICP) technology and the combined effect of MICP technology and lignin on the improvement of silt in the Beijing area. Through unconfined compressive strength and dynamic triaxial test methods, samples improved by microorganisms were studied to obtain the optimal values of cement concentration and lignin under these two test schemes. The results show that after the incubation time of Sporosarcina pasteurii reached 24 h, the OD600 value was 1.7-2.0 and the activity value (U) was 930-1000 mM ms/min. In the unconfined static pressure strength test, after MICP treatment the optimal concentration of cementitious solution for constant temperature and humidity samples and constant-temperature immersion samples was 1.25 mol/L. The compressive strength of the constant temperature and humidity sample was 1.73 MPa, and the compressive strength of the constant-temperature immersion sample was 3.62 Mpa. At the concentration of 1.25 mol/L of cement solution, MICP technology combined with lignin could improve the constant temperature and humidity silt sample. The optimal addition ratio of lignin was 4%, and its compressive strength was 1.9 MPa. The optimal lignin addition ratio of the sample soaked at a constant temperature was 3%, and the compressive strength was 4.84 MPa. In the dynamic triaxial multi-stage cyclic load test, the optimal concentration of cementation solution for the constant temperature and humidity sample after MICP treatment was 1.0 mol/L, and the failure was mainly inclined cracks. However, in the condition of joint improvement of MICP and lignin, the sample mainly had a drum-shaped deformation, the optimal lignin addition ratio was 4%, and the maximum axial load that the sample could bear was 306.08 N. When the axial dynamic load reached 300 N, the strain accumulation of the 4% group was only 2.3 mm. In this paper, lignin, an ecofriendly material, was introduced on the basis of MICP technology. According to the failure shape and relevant results of the sample, the addition of lignin was beneficial for the improvement of the compressive strength of the sample.

Experimental Study on Different Improvement Schemes of EICP-Lignin Solidified Silt.

In practical engineering applications, silt is prone to liquefaction and quicksand. This paper mainly studies the improvement effects of urease, lignin and their mixture on the strength and liquefaction resistance of silt. Based on the results and phenomena of an unconfined compressive strength and dynamic triaxial test, the improvement effects of the compressive strength, deformation resistance and liquefaction resistance of silt under different improvement schemes are analyzed, and the optimal values of the cement or lignin when enzyme-induced calcium carbonate precipitation (EICP) technology, lignin alone or EICP and lignin are obtained. The results show that the optimum concentration of the constant temperature and humidity sample (referred to as the constant humidity sample) and the constant temperature immersion sample (referred to as the soaking sample) of urease in the unconfined compressive strength test is 1.0 mol/L, and the compressive strength of the soaking sample is 4.9 MPa, which is 1.56 times that of the constant humidity sample; the optimum addition ratio of the lignin-improved constant humidity sample is 3%, and its compressive strength is 2.07 Mpa; the optimum addition ratio of the samples immersed at constant temperature is 4%, and the compressive strength is 3.05 MPa; when urease combines with lignin to improve silt, 4% is the best lignin addition ratio, the compressive strength of the constant humidity sample reaches 1.57 Mpa and the compressive strength of the soaking sample reaches 3.75 MPa; in the dynamic triaxial multi-stage cyclic load test, all samples were cured at constant humidity sample, and in the urease modified silt scheme, 1.0 mol/L was the optimal cement concentration; in the scheme of improving silt with lignin, 3% is the optimal addition ratio; when 1.25 mol/L cementation solution plus urease crude extract is combined with different ratios of lignin in the experimental scheme, 3% is the best lignin addition ratio.

Experimental Study on the Influence of Different Factors on the Mechanical Properties of a Soil-Rock Mixture Solidified by Micro-Organisms.

In this paper, we focus on the application of mechanical properties in a soil-rock mixture modified by microbial mineralization under the influence of different factors, including pH value, cementing solution concentration, and cementing time. Cementing fluids and samples with different pH values, calcium ion concentrations, and mineralization cementation were prepared. The process of urea hydrolysis MICP under different factors was studied. A solidified soil-rock mixture sample under triaxial compression was measured. Then, combined with scanning test methods, such as SEM and XRD, the influence of different factors on the mechanical strength and failure mode of the soil-rock mixture structure was analyzed from a microscopic point of view. The results show that a low concentration of cementing solution with a high concentration of bacteria liquid generated the highest calcium carbonate content and the strongest cementing ability. When the pH value of the cementation solution is six, the cementation effect between the pores is the best, and the deviatoric stress is stronger. When wet-curing samples, short or long curing time will adversely affect the strength of soil-rock mixture samples, the strongest curing and cementing ability is 5 days. The microscopic results show that the microbial mineralization technology fills the pores between the particles, and the interaction force between particles is enhanced to enhance the strength of the soil-rock mixture.

Study on Ultrasonic Nondestructive Testing of Self-Compacting Concrete under Uniaxial Compression Test.

To study the variation law of ultrasonic parameters of self-compacting concrete before and after damage under uniaxial compression test conditions, the C30 self-compacting concrete blocks stored for 7 days and 28 days were subjected to ultrasonic nondestructive testing, and the variation law of the sound time, amplitude, and sound velocity before and after the damage of self-compacting concrete blocks was emphatically analyzed. The concrete acoustic detection software was introduced to judge and analyze the abnormal values of the parameters of each measuring point, and the defect distribution map of each test block was obtained. The results showed that after curing the self-compacting concrete test block for 7 days and 28 days, the average value of sound time before and after the failure of each measuring point of the test block is small, and the average value of sound time before the failure is less than that after; the average amplitude after failure is smaller than that before failure, and the amplitude of some measuring points will be smaller than that before. The average sound velocity after failure is less than that before failure, and the internal defects appear and the structure is not dense. This study provides a theoretical basis for the application of ultrasonic detection technology in the field of self-compacting concrete and also provides a practical basis for the stability monitoring and failure warning of self-compacting concrete.

Role of Na-Montmorillonite on Microbially Induced Calcium Carbonate Precipitation.

The use of additives has generated significant attention due to their extensive application in the microbially induced calcium carbonate precipitation (MICP) process. This study aims to discuss the effects of Na-montmorillonite (Na-MMT) on CaCO3 crystallization and sandy soil consolidation through the MICP process. Compared with the traditional MICP method, a larger amount of CaCO3 precipitate was obtained. Moreover, the reaction of Ca2+ ions was accelerated, and bacteria were absorbed by a small amount of Na-MMT. Meanwhile, an increase in the total cementing solution (TCS) was not conducive to the previous reaction. This problem was solved by conducting the reaction with Na-MMT. The polymorphs and morphologies of the CaCO3 precipitates were tested by using X-ray diffraction and scanning electron microscopy. Further, when Na-MMT was used, the morphology of CaCO3 changed from an individual precipitate to agglomerations of the precipitate. Compared to the experiments without Na-MMT in the MICP process, the addition of Na-MMT significantly reduced the hydraulic conductivity (HC) of sandy soil consolidated.

Effectiveness and safety of low-dose apatinib in advanced gastric cancer: A real-world study.

Apatinib has been demonstrated to be effective and safe among patients with gastric cancer failing after at least two lines chemotherapy. This study aimed to evaluate its effectiveness and safety of low-dose apatinib for the treatment of gastric cancer in real-world practice. We performed a prospective, multicenter observation study in a real-world setting. Patients with advanced gastric cancer more than 18 years old were eligible and received low-dose apatinib (500 mg or 250mg per day) therapy. The median progression-free survival (PFS), median overall survival (OS), objective response rate (ORR), disease control rate (DCR), and safety were assessed. Between September 2017 and April 2019, a total of 747 patients were enrolled. The mPFS was 5.56 months (95% CI 4.47-6.28), and mOS was 7.5 months (95% CI 6.74-8.88). Four patients achieved complete response, 47 achieved partial response, and 374 patients achieved stable disease. The ORR was 6.83% and DCR was 56.89%. In addition, multivariate Cox regression analysis indicated that hand-foot syndrome was one independent predictor for PFS and OS. The most common adverse events (AEs) at any grade were hypertension (36.55%), proteinuria (10.26%), hand-foot syndrome (33.53%), fatigue (24.9%), anemia (57.35%), leukopenia (44.49%), thrombocytopenia (34.21%), and neutropenia (53.33%). Grade 3-4 AEs with incidences of 5% or greater were anemia (13.97%), thrombocytopenia (7.14%), and neutropenia (6.67%). No treatment-related death was observed during the treatment of apatinib. The prospective study suggested that low-dose apatinib was an effective regimen for the treatment of advanced gastric cancer with tolerable or controlled toxicity in real world. Trial registration: NCT03333967.

Pathological complete response from oral chemotherapy combined with trans-arterial chemotherapy and embolization in an unresectable gastric cancer patient: A case report.

RATIONALE: Gastric cancer is still one of the most common cancer in East Asia. More than 70% gastric cancer patients are diagnosed at an advanced stage in China. Moreover, about 10% cases are unresectable which usually suffer a poor prognosis with a median survival time of 5 to 12 months. In recent years, some clinical studies found that many unresectable gastric cancer cases could get opportunity for surgery after treatment that improve prognosis significantly PATIENT CONCERNS:: 64-year-old male patient was admitted with upper abdominal pain. Upper gastrointestinal endoscopy showed a large ulcerated tumor located from the cardia to the anterior wall of the upper gastric body. Histopathological examination showed it was moderately differentiated adenocarcinoma. Computed tomography (CT) scan image showed a large bulging mass with internal ulcer at the lesser curvature wall, left gastric artery and coeliac trunk were surrounded by fused lymph nodes. DIAGNOSES: Based on the histopathological examination and imaging findings, patient was diagnosed advanced gastric cancer and hardly to resect radically. INTERVENTION: Oral chemotherapy combined with trans-arterial chemotherapy and embolization (TACE) was initiated. Eight weeks after initial therapy, radical laparoscopy-assisted total gastrectomy with D2 lymph node dissection and Roux-en-Y anastomosis were performed successfully. OUTCOMES: Patient was discharged on postoperative day 11 without complications. Histological analysis of the specimen and resected 31 lymph nodes revealed no malignancy. The patient experienced a pathological complete response (pCR). LESSONS: In this case, oral chemotherapy combined with TACE which was rarely reported in the treatment of unresectable gastric cancer achieves a great therapeutic benefit. Although further clinical studies will be needed to establish, it may be a potent strategy for degrading stage and supplying a new chance for surgery.

lncRNA GAS5 inhibits colorectal cancer cell proliferation via the miR­182­5p/FOXO3a axis.

Long non­coding RNAs (lncRNAs) are mainly involved in diverse biological processes in human malignancies. The expression profile and underlying mechanism of the lncRNA growth arrest specific transcript 5 (GAS5) in colorectal cancer (CRC) are poorly understood. Here, we investigated the role of GAS5 in human CRC tissues. lncRNA GAS5 was specifically downregulated in CRC tissues and cell lines. Reduced GAS5 levels were significantly associated with advanced clinical stage and lymph node metastasis in CRC. GAS5 overexpression suppressed CRC cell proliferation and promoted cellular apoptosis. A dual­luciferase reporter assay showed that GAS5 could negatively regulate the expression of microRNA (miR)­182­5p. Upregulated miR­182­5p abrogated the effect of GAS5 overexpression on CRC cell proliferation and apoptosis. Furthermore, GAS5 positively regulated the expression of FOXO3a in CRC cells. Taken together, these findings suggest that overexpression of the lncRNA GAS5 inhibits cell proliferation and promotes apoptosis by inhibiting miR­182­5p expression, and thus could be a therapeutic target in CRC.

Laparoscopy-Assisted D2 Radical Gastrectomy for Advanced Gastric Cancer.

BACKGROUND/AIMS: The aim of this study was to investigate the efficacy and advantages of laparoscopy-assisted gastrectomy (LAG) with D2 lymphadenectomy versus conventional open D2 gastrectomy (ODG) in advanced gastric cancer (AGC) patients. METHODOLOGY: From June 2009 to June 2014, 233 patients who were treated by conventional radical ODG and 188 cases who underwent radical LAG for AGC at our department were enrolled in this study. Clinical data recorded in hospital database was retrospectively reviewed and analyzed. RESULTS: There were no significant differences in age, gender or preoperative laboratory tests distribution between the LAG group and the ODG group. Two (1%) of the patients who underwent LAG required conversion to ODG. The advantages of minimally invasive surgery including earlier recovery of bowel movements and shorter postoperative hospitalization time were observed in LAG group. The number of harvested lymph nodes was 24.3 ± 3.3 in the LAG group and 25.0 ± 2.8 in ODG (p = 0.110). CONCLUSIONS: Although prospective randomized trials with long follow-up period are needed to identify the feasibility, we have shown the safety and advantages of LAG with D2 lymphadenectomy for treating AGC patients in this study.

Sentinel lymph node and skip metastases in gastric cancer: a prospective study.

BACKGROUND/AIMS: The aim of the present study was to investigate localization and distribution of sentinel lymph node (SLN) in gastric cancer and influenced factors of skip metastasis. METHODOLOGY: Eighty-nine cases with solitary or single station metastatic lymph nodes (LNs) among 779 gastric cancer patients were included in this study. D2 or D2+ lymph node dissection with total or distal gastrectomy had been performed. The location of SLNs and characteristics were analyzed retrospectively. RESULTS: Seventy-one patients (79.8%) had SLNs at the first level of the regional LN group and 18 cases (20.2%) had skip metastases SLNs. NO.7 (44.4%) and NO.8a (27.8%) were the most common sites of skip metastases. Multivariate analysis identified the differentiated degree of tumor as the only significant influenced factor of skip metastases (p=0.031). The number of metastatic SLNS was significantly greater in advanced gastric cancer patients (2.4 ± 1.4) than early gastric cancer patients (1.5 ± 0.9) (pT4 vs. pT1, p=0.002; pT4 vs. pT2, p=0.014; pT3 vs. pT1, p=0.018). CONCLUSIONS: The differentiated degree of gastric cancer is the most important influenced factor of skip metastases and NO.7 and NO.8a are the most important N2 LN stations that should be observed when lymphadenectomy is performed.